At the Brink of Extinction Why?
webpage assembled by Connie Barlow
founder of Torreya Guardians
(latest update November 2022)
HOW TO USE THIS WEBPAGE: This webpage has been online (and periodically updated) for more than a dozen years. However, in 2019 it seemed time to reconfigure the text for ease of use and to distinguish the background, objective summaries (with key links) from my own advocacy sections. Two events in 2018 indicated a reconfiguration was in order: In March 2018, genetic engineering of the Torreya genome was advocated by a University of Florida forest pathologist. And in August of 2018 the U.S. Fish & Wildlife Service announced that the 2010 recovery plan would be updated. The recovery plan for Florida Torreya was updated in 2020 and marginalized the "assisted migration" poleward strategy, compared with the more expansive 2010 plan. (Access the 2020 Revised Plan, along with comments.)
Necessarily, this "extinction" webpage now has to deal with the sudden turn in official institutional thinking toward single-agent disease focus, which began in 2011. Nevertheless, the original "extinction" webpage on the Torreya Guardians site that focused on the PALEOECOLOGY AND GEOGRAPHY aspects of the GLACIAL RELICT understanding of Florida Torreya is as relevant as ever. Thus the webpage highlighting key glacial relict points initiated by Connie Barlow in 2010 is recommended for all as background. A core excerpt follows:
EXCERPT: WHAT PREVENTED THIS GLACIAL RELICT FROM RETURNING NORTH?
... 7B. An alternative hypothesis is that the large-seed of Torreya (which is sometimes capable of floating for several days) easily caught a fast and obstacle-free river ride southward from the Appalachian Mountains by way of the Chattahoochee River at the onset of cooling during the Pliocene or Pleistocene. But there was no river-flow way to return north during any of the interglacial warmings. In the first half of the 20th century, the add-on of human-caused warming finally surmounted the physiological threshold of genus Torreya, and it was no longer able to ward off more than a half-dozen native diseases. The fact that the Florida Yew, Taxus floridana is also a subcanopy rare endemic limited to the same relictual range as Florida Torreya suggests that river-flow assistance may truly be limiting. After all, the seed of Florida Yew is bird-dispersed; dispersal by birds offers faster and greater long-distance distribution than can squirrels or tortoises.
• VISIT THE "PALEOECOLOGY" PAGE FOR FLORIDA TORREYA on this website, for a detailed and illustrated explanation of the evidence and arguments that this ancient subcanopy species once occupied an area of North America far poleward of its present, refugial location.
UPDATE OCTOBER 2021: The threat of genetic engineering seems to be defused, owing in part to the USF&WS decision on "PETITION TO DOWNLIST FLORIDA TORREYA", which was filed by Connie Barlow September 2019. The agency published its decision 29 September 2020, with language that quenched focus on the previously implied single disease agent, Fusarium torreyae, which in 2018 had led to mention of genetic engineering as a potential response. Excerpts of the 2021 decision will be included in relevant sections below. On the negative side, the 2021 agency decision backtracked on all previous agency publications on the matter of Florida Torreya as a bona fide glacial relict. In the petition decision "glacial relict" status of Florida Torreya was, for the first time, cast into doubt.
LINKED LIST OF TOPICS WITHIN THIS EXTINCTION WEBPAGE
Part 1. Overview and History: Quest to Determine Cause (background and sources)
Part 2. Ascertaining the Ultimate Cause of the Proximate Disease (background, sources, advocacy)
Part 3. Assisted Migration of Glacial Relicts, Not Genetic Engineering (background, sources, advocacy)
Part 4. Torreya taxifolia = Climate Adaptation Case Study in Conservation Biology (advocacy, sources)
Part 5. U.S. Forest Service Leads the Way in Assisted Migration Policy (background, sources)
Part 6. CONCLUSION: Assisted Migration Now (advocacy and previous advocacy publications by Barlow)
Part 1 - "Overview and History" is a streamlined way to learn (and access key links) of the quest to find the cause(s) of Torreya's inability to thrive and reproduce in its small native range in Florida. It is intended to be a reliable, objective way to quickly learn the background and to access the source documents.
Part 2 - "Ultimate Cause", while serving as advocacy, points to key sources as a reminder that it is crucial to ascertain the ultimate cause of a proximate disease cause and that the ongoing dispute about ultimacy is still an important factor for evaluating proposed recovery actions and plans. It is also crucial to actually read the academic papers, rather than accepting statements made in media reports or blogs as accurate representations of peer-reviewed science.
Part 3 - "Assisted Migration" provides the history of this line of advocacy for Florida Torreya (based on its undisputed status as a "glacial relict"), as well as the post-2008 surge of academic papers and news reports on assisted migration as a climate-adaptation response for even common forest trees. Hence, the 2019 recovery plan update takes place within the context of assisted migration having become a prominent conservation issue and with Florida Torreya now widely regarded as the foundational case study.
Part 4 - "Climate Adaptation Case Study" is included on this page as notice for decisionmakers, journalists, and activists that, since 2008, the actions of Torreya Guardians and the decisions and actions (including nonactions) made by the official agency and implementing institutions of this listed endangered species is a leading and widely watched example of whether and how traditional standards for ascertaining native range and native species will need to be adapted owing to ongoing rapid climate change. Staff members and advisors officially engaged in the scheduled 2019 recovery plan update for this species should be aware of this larger context. UPDATE: The official recovery plan was updated in 2020 and appears to be even less open to the benefits of assisted migration to help this Florida glacial relict escape diseases than previous versions of the recovery plan.
Part 5 - "U.S. Forest Service Leads the Way in Assisted Migration Policy" puts into federal context the long-standing U.S. Fish and Wildlife Service hesitancy to utilize the Florida Torreya case as perhaps the ideal opportunity to responsibly begin to experiment with an assisted migration component to endangered species management plans in this time or increasing climate change. Here, a 2018 report by the U.S. Forest Service expressly on "assisted migration" is excerpted. More USFS reports on the necessity for "climate adaption" (along with examples ongoing in Canadian forests) can be accessed at this forestry section of "Assisted Migration Scholarly Links" webpage, originated by Barlow a dozen years ago. UPDATE 2021: Barlow collaborated with a Canadian to establish a new, and scholarly referenced, page on WIKIPEDIA titled "Assisted migration of forests in North American". This wikipedia page includes sections that present the policy and action leadership (and scholarly papers) by governmental forestry staff in both the USA (USDA) and Canada.
Part 6 - CONCLUSION: "Assisted Migration Now" (by Connie Barlow) is a brief summary of advocacy, with UPDATES.
Part 1. Overview and History: Quest to Determine Cause
1A. OVERVIEW SOURCES ON THE DEGREE OF DIEBACK (AND POSSIBLE CAUSES)• WIKIPEDIA ENTRY - Torreya taxifolia ("Critically Endangered Species" section)1B. TORREYA'S SLIDE INTO ENDANGERMENT WAS SUDDEN AND HAPPENED MORE THAN 50 YEARS AGO
• Center for Plant Conservation: Profile of Torreya taxifolia
• Chasing Ghosts: The steep ravines along Florida's Apalachicola River hide the last survivors of a dying species, Torreya taxifolia, by Rob Nicholson, 1990, Natural History Magazine
A 1962 "letter" in Science by R.K. Godfrey and Herman Kurz, "The Florida Torreya: Destined for Extinction, is often cited as the foundational publication that established the degree of loss and the short time interval in which it occurred Excerpt:"One of us (H. K.) recalls very well having escorted in 1954, two parties of botanists to two localities along the Apalachicola River to view Florida torreya. No one present noticed anything abnormal about the trees. Since that time there has been a diminution in their number, and recently we decided to make a special trip to determine the present status of the torreya. On 17 March 1962 we visited and thoroughly explored the Jackson County site and two places east of the Apalachicola River, at Aspalaga and at Rock Bluff. We learned that only a few abortive sprouts survive. The culprit? Apparently, a fungal disease of the stems. We know nothing more than that."
LEFT: A few months later, a "letter" was published in the same journal, which explained rescue efforts by the Florida Park Service:
1C. MULTIPLE DISEASE AGENTS WERE STUDIED FOR DECADES (no consensus reached)
• Excerpt from the original 1986 Recovery Plan (pp. 5-6; emphases added):A current list of fungi associated with diseases of Torreya taxifolia is as follows (Alfieri et al., 1984):• Excerpt from the 2010 Recovery Plan Update (p. 5; emphases added)
Recently, Fusarium lateritium was isolated from spots on needles of 30-year-old-Florida torreya trees.... There is a possibility that an introduced, non-native pathogen such as Phytophthora cinnamomi is involved (Barnard 1985).
The occurrence of multiple fungi, some of them known to be soil inhabitants and opportunistic pathogens of several plant species, suggests that the fungal infections are merely symptoms of another underlying cause of decline (Kurz 1938, Mundkur 1949, Hartman and Kester 1968, Alfieri 1983, Barnard 1985). Barnes (1983b, 1984) noted that the major episodes of torreya dieback have occurred following periods of drought. Major diebacks of mature torreya trees occurred in the late 1930s and the late 1950s (Godfrey and Kurz 1962, Alfieri et al. 1967). In both cases, 4 to 7 years of below average rainfall preceded diebacks. Drought stress renders plants more vulnerable to fungus infections. But torreya has presumably survived droughts in its native habitat for millenia; this suggests that other factors may have contributed to the decline.
Torreya appears to occupy sites where a steady supply of cold moisture is available from seepage, and where it is shady in the summer. Soil moisture at these sites may have been affected by alteration of the pine forests on uplands above the ravines (Clewell 1977, Kurz 1938b), which altered the drainage and retention of surface and ground water, in turn probably altering seepage into the ravines. Logging has altered the forests in the ravines (Reinsmith 1934). Concern has also been expressed over changes in the microclimates of the ravines that may have been caused by construction of the Jim Woodruff Dam, completed in 1956. This impoundment altered the Apalachicola River flooding cycle and raised downstream water temperatures, which possibly raised air temperatures near the river (Toops 1981) resulting in a change of microclimate. No inquiry has been made into the possible effects of air or water pollution. It is possible that relatively minor human alterations of the habitat may seriously affect torreya; it is possible that the present-day physical environment of the Apalachicola bluffs and ravines is only marginally suitable to Florida torreya. The species may be restricted to the area because it failed to migrate northward at the end of the Pleistocene.Identify pathogen(s) responsible for the decline: This is an ongoing action that goes back to 1967 (Alfieri et al. 1967). The authors observed that the stem and needle blight disease of T. taxifolia appears to be incited by a fungus causal agent implicating Physalospora and Macrophoma. Alfieri et al. (1987) isolated six other fungi from leaves and stems of T. taxifolia. Lee et al. (1995) isolated more than 30 different endophytic fungi, but consistently, Pestalotiopsis microspora (a fungus that resides in the inner bark of symptomless T. taxifolia trees) was found on diseased trees. They concluded that the pathological activity of this fungus could be triggered by physiological and/or environmental stress.• "Root and Soil-borne Oomycetes (Heterokontophyta) and Fungi Associated with the Endangered Conifer, Torreya taxifolia in Georgia and Florida", by Lydia I. Rivera Vargas and Vivian Negron-Ortiz, 2013, chapter in book (25 pp; highly detailed academic writing).
Herman and Schwartz (1997) studied the pathogenicity of Scytalidum sp. They inoculated both needles and stems causing needle spots and necrosis, but couldn't provide evidence that it was the cause of the original decline of T. taxifolia. Soil-borne pathogens, such as Phytophthora sp., Pythium sp., Rhizoctonia solani and Sclerotium rolfsii have been reported on T. taxifolia. At present, Dr. Lydia Rivera (Univ. of Puerto Rico, 2009) is conducting a soil-borne pathogen survey, emphasizing the detection of Phytophthora spp. She isolated 102 fungi from TSP, FL, and Corps property, GA. Of the trees surveyed, 48 % had root necrosis and stem cankers. She is designing a pathogenicity test associated with potential disease outbreaks.
Dr. Jason Smith (Univ. of Florida) is conducting an above-ground plant pathogen study. He isolated numerous fungi from cankers and consistently found an undescribed Fusarium sp.; he is working with a specialist in Japan to describe the new Fusarium species. According to Smith (2010, pers. comm.), "inoculation experiments with seedlings and larger potted torreyas have provided ample evidence that Fusarium is the causal agent" for the current population decline; the cause of the initial decline remains unknown. When plants are inoculated with Fusarium, it leads to canker development, lesions, and mortality (Smith 2010, pers. comm.). He proposes to elucidate the disease biology, as well as conductive epidemiological factors and treatment. Aaron Trulock is a graduate student under Smith and will be doing his research on the biology of canker disease of the T. taxifolia.EXCERPTS and TABLES: ... Several Fusarium species have been shown pathogenic to T. taxifolia, by causing needle spots, i.e. F. lateritium Nees (El-Gholl 1985, Alfieri et al. 1987), and has been associated with root rot (Alfieri et al. 1984). More recently, a novel described species F. torreyae Aoki, Smith, Mount, Geiser, and O’Donnell, was demonstrated to be the causal agent of stem cankers (Smith et al. 2011). Until now, no Fusarium spp. has been demonstrated to cause cankers comparable to those observed in the field. In other conifer species, F. oxysporum Schltdl. Emend. Snyder and Hansen has been associated with seedling death and root rot (Viljoen et al. 1992).
... In this study, various Fusarium species (anamorph of Gibberella spp.) were isolated in both locations from roots and associated to bark, plant litter and dying trees. From Georgia, Fusarium oxysporum was isolated from roots and plant litter. This species has been associated with seedling death and with root rot in Pinus and Eucalyptus seedling in South Africa (Viljoen et al. 1992). Fusarium solani was also isolated from roots of dying trees at this site (Table 3). Based on macroconidia and chlamydospores morphology, none F. torreyae was isolated during this study (Aoki et al. 2013). Recently this species have been shown to cause Torreya canker disease in Florida (Smith et al. 2011). DNA analysis of the ITS rDNA region showed that Fusarium spp. isolated during this study were closed to F. subglutinans, F. oxysporum and Gibberella spp. clades (Figure 5). However, amplification of other more informative genetic regions such as RNA polymerase largest subunit (RPB1 and RPB2) was not employed during this study....
SEE PHOTOS OF LEAF AND STEM PATHOLOGIES ON TORREYA: disease photos.
1D. LETHAL FUSARIUM PATHOGEN IDENTIFIED IN THE 2010s AND IMPLIED AS PROXIMATE CAUSE UNTIL 2020In 2010, Prof. Jason Smith, a forest pathologist at the University of Florida, Gainesville, undertook pathology research culminating in a series of papers that (a) identified an oomycete (water mold) that caused stem cankers as being the cause of current lethal pathology, and (b) concluded that the Fusarium was sufficiently different from the previously identified pathogen afflicting torreya (Fusarium lateritium) to merit naming as a new species: Fusarium torreyae.
Peer-reviewed Fusarium papers by Jason Smith:• "A Novel Fusarium Species Causes a Canker Disease of the Critically Endangered Conifer, Torreya taxifolia", by Jason A. Smith et al., Plant Disease, June 2011, 7 pp. with photos.Non peer-reviewed papers by Jason Smith and/or student:
• "Fusarium torreyae sp. nov., a pathogen causing canker disease of Florida torreya (Torreya taxifolia), a critically endangered conifer restricted to northern Florida and southwestern Georgia", by Takayuki Aoki, Jason A. Smith, Lacey L. Mount, David M Geiser, Kerry O'Donnell, 2013, Mycologia.
• "Two novel Fusarium species that cause canker disease of prickly ash (Zanthoxylum bungeanum) in northern China form a novel clade with Fusarium torreyae", by Zhou Xue, Kerry O'Donnell, Akayuki Aoki, Jason A. Smith, Matthe T. Kasson, Zhi-Min Cao, 2016, Mycologia.
• "Detection method for Fusarium torreyae the canker pathogen of the critically endangered Florida torreya, Torreya taxifolia", by Tyler J. Dreaden, Tania Quesada, Jason A. Smith, 2020, Forest Pathology. NOTE: This 2020 paper refrains from speculating that F. torreyae may have a non-native origin, and does not conclusively state that this pathogen was the cause of 1950s torreya blight in Florida.
Access annotations of all these pathogen papers here.• "The Decline of Florida Torreya: An Endemic Conifer on the Edge of Extinction", by Jason A. Smith and Aaron Trulock, 2010, University of Florida School of Forest Resources and Conservation, research paper.1E. 2018 TORREYA SYMPOSIUM REPORTS DISEASE CONSENSUS; LAUNCHES GENETIC ENGINEERING ADVOCACY
• "Host Range and Biology of Fusarium torreyae, Causal Agent of Canker Disease of Florida Torreya, by Aaron J. Trulock, 2012, 55 pp., (master of science thesis, University of Florida)• 2018 Torreya Symposium Announcement and Speaker List. News reports and blogs on the symposium:
• "For Endangered Florida Tree, How Far to Go to Save a Species?", by Janet Marinelli, 27 March 2018, Yale Environment 360 (2,300 words)EXCERPT: ... Although few scientists fear that the transgenic chestnut would result in a 'super tree' capable of overrunning Eastern forests, the public is still jittery about genetic engineering. An impartial committee has been convened by the National Academy of Sciences to study "the potential of biotechnology to address forest health." Its report is expected at the end of this year. In part to sidestep the controversy, Smith is hoping to use CRISPR to, in his words, "toggle up" disease resistance in the Florida torreya's own genes. Given the tree's imminent extinction along the Apalachicola, he says, "regular breeding is too slow." CRISPR exploits a natural ability of bacterial immune systems to identify and disable invading viruses. Scientists create short RNA sequences that attach to corresponding sequences in the receiving species' DNA. This molecular guidance system is paired with an enzyme that originally was designed to snip the DNA, "knocking out" a targeted gene. Using modified versions of the enzyme, it is now possible to activate or increase gene expression....• "Scientists outline novel approach to save endangered torreya tree", by Samantha Grenrock, Tallahassee Democrat, 05 April 2018. (Note: Grenrock is a "public relations specialist" at University of Florida; the Tallahasee Democrat article is drawn from her blog on the UF site.)EXCERPT: ... Finally, scientists will begin screening trees to look for those resistant to the fungus that’s so devastated the species. Scientists will then determine which genes in these resistant trees make them more resilient. If they can identify this genetic component, the gene editing technology CRISPR can be used to produce trees that have these traits, Smith said. "When funded, this holistic strategy, involving many scientists and institutions, could give us a fighting chance at saving the torreya. This isn't typically how conservation is done, so we're excited to be trying this novel approach," Smith said. "With the rate at which genetic technologies are advancing, as well as the programs we already have in place, the goal is to have a method we can implement in the next three to five years."• A Tallahassee TV station conducted a 4-minute VIDEO interview with Jason Smith (as of March 2019, no longer available online.)
• "Saving the Torreya: Workshop Brings Scientists and Conservation Leaders Together", by Sarah Farmer, in USDA Southern Research Station, CompassLive, 8 May 2018.
• "Travels of a 'Real Naturalist'", by Rob Nicholson, Botanical Collections Manager, Spring 2018 in Friends of Wellesley College Botanic Gardens, 1 page pdf where Nicholson reports on his speaking at the Torreya Symposium in March, including his role in collecting and rooting branchlets of wild specimens, beginning in the 1980s.
• "Saving the Endangered Torreya taxifolia", by Adam Black, article in March 2018 newsletter of Peckerwood Garden Conservation Foundation, multi-page illustrated report of his experience at the Torreya Symposium.
• "'Ice Age' Tree in Peril: Florida Torreya", by Sheila Dunning, 14 April 2019, University of Florida Extension Service.EXCERPTS: ... The Florida Torreya (Torreya taxifolia) is one of the oldest known tree species on earth; 160 million years old. It was originally an Appalachian Mountains ranged tree. As a result of our last "Ice Age" melt, retreating icebergs pushed ground from the Northern Hemisphere, bringing the Florida Torreya and many other northern plant species with them. The Florida Torreya was "left behind" in its current native pocket refuge, a short 40 mile stretch along the banks of the Apalachicola River. There were estimates of 600,000 to 1,000,000 of these trees in the 1800’s. Torreya State Park, named for this special tree, is currently home to about 600 of them. Barely thriving, this tree prefers a shady habitat with dark, moist, sandy loam of limestone origin which the park has to offer.1F. 2019 ARTICLE REPORTS ATLANTA BOTANICAL GARDEN DISAGREES THAT GENETIC ENGINEERING IS NECESSARY NOW
... There is great concern for this ancient tree in the scientific community and with citizen organizations. Efforts are underway to help bring this tree back from the edge of extinction! Efforts include CRISPR gene editing technology research being done by the University of Florida Dept. of Forest Resources and Conservation making the tree more resistant to disease. Torreya Guardians "rewilding" and "assisted migration". Reintroducing the tree to its former native range in the north near the Biltmore Estate in Asheville, NC, which has maintained a grove of Torreya trees and offspring since 1939 and supplying seeds for propagation from their healthy forest....• "The Race to Save the Most Endangered Conifer in America", by Brian Kahn, 9 April 2019, Earther.EXCERPTS: .... This ex situ collection of trees [at Atlanta Botanical Garden] form a cornerstone of the recovery plan. Scientists here and with the University of Florida are monitoring them to see which have proven resistant to the fungus and have also been using the clippings to help sequence their genomes. [Emily] Coffey [of Atlanta Botanical Garden] said the analysis will help "see how distinct each individual tree is." If scientists can find out what makes the trees that can handle the fungus tick, they could crossbreed them. There has even been talk of using CRISPR, a revolutionary new genetic engineering tool, that could open up a fast track to editing torreya genes.1G. 2021 UPDATE: USF&WS MAIN TORREYA PAGE SIDELINES THE "EXOTIC" PATHOGEN, SINGLE-CAUSE OF LONG-TERM TORREYA DECLINE
Coffey said anything involving CRISPR is likely 10-15 years down the road, though. In the near term, her group and their partners are also doing experiments with fungicides. And in February, they installed sensors near some trees in North Florida that can assess temperature, humidity, and sun exposure. That data can then be cross-referenced with how the trees deal with fusarium fungus in the hopes tracking what conditions make the outbreak better or worse.
It's all a race against the clock as trees wither away in the wild. And the fallout from Hurricane Michael could open up the ravines to even more punishment than the immediate canopy loss. The lack of tree cover means the ravines could become hotter and drier, and with downed wood everywhere, the risk of previously unheard of fires is on the rise. Just over a week ago, a blaze ignited near Panama City that firefighters couldn't contain until it burned 600 acres. A similar fire in the steephead ravines could deal a major blow to the torreya still clinging to life there....• U.S. Fish & Wildlife Service page: "Florida torreya (Torreya taxifolia):GENERAL INFORMATION: Torreya taxifolia Arn. is an evergreen conifer endemic to the slopes of the Apalachicola River presently located in two Florida panhandle counties and one county in Georgia. T. taxifolia has lost at least 98.5% of its total population size since the early 1900s, causing that this species be federally listed as endangered. The loss of T. taxifolia is thought to have primarily been a result of fungal pathogens during the 1950s and 1960s, and/ or a combination of environmental stress and native pathogens, but studies have yet to provide an explanation for this species decline. The pathogen F. torreyae is a key contributor to the continued decline of this species. The magnitude of stem damage caused by deer rubbing represents a current threat; the vascular cambium is rubbed off causing an aperture for fungal infection. Overcollection was a threat of high importance in the past, but at present is not of concern. Despite the conservation actions to protect and determine the cause of this species decline, the degree of threat to its persistence remains high; therefore, the threat of extinction that faces T. taxifolia is imminent. [emphases added]• USF&WS "Record of Actions" for Torreya taxifolia includes mention of a "different" pathogen of the same (Fusarium) genus that is causing cankers on the California species of Torreya:ACTION #34: Conduct grafting experiments: "The recovery plan suggests grafting [asexual propagation where the tissues (vascular cambium) of one plant are fused with those of another] with T. californica. However, T. californica is exhibiting some issues with cankers caused by pathogens with a different Fusarium species which is killing the cambium."1H. 2021 UPDATE: USF&WS PUBLISHES A "DECISION" ON THE 2019 "PETITION TO DOWNLIST" (that Connie Barlow filed in Sept 2019) and this decision REMOVES THE FOCUS OF FUSARIUM TORREYAE AS A SINGLE, DOMINANT CAUSE OF TORREYA DELCINE.• U.S. Fish & Wildlife Service "DECISION" on the "Petition to Downlist", which was filed by Connie Barlow Sept 2019.IMPORTANCE: This decision returns to the pre-2018 inferred conclusion that multiple disease agents were and are at cause (at least proximately) for Florida Torreya's inability to thrive and reproduce within the geographic limits of its narrow endemic range in the Florida panhandle. On the other hand, for the first time, the status of Florida Torreya as a bona fide glacial relict is cast into doubt. The update in "disease agent" is excerpted here in the para below. Retrenchment in characterization of Florida Torreya as a "glacial relict" will be excerpted in Section 3A.DISEASE EXCERPT: "... The primary decline in species abundance is thought to have resulted from fungal pathogens during the 1950s and 1960s, and/or a combination of environmental stress and native pathogens, but studies have yet to provide an explanation. As a result, the main threat for this species' decline is still not well understood, even though considerable research and management activities have been and are presently conducted on this species."
Part 2. Ascertaining the Ultimate Cause of the Proximate Disease
NOTE: You may advance directly to the section that LINKS AND EXCERPTS♦ Notice by Connie Barlow: Links and logic shift to advocacy at this point. All of the links and annotations in Part 1 should be noncontroversial, as the above series presents a straightforward history (with key citations linked) on scientific observations, research, and contentions on the issue of WHY Florida torreya is rapidly failing in its native range.
RECENT PAPERS ON STEM CANKER PATHOLOGY (Fusarium torreyae).
2021 UPDATE: April 2021 Connie Barlow accessed the main Florida Torreya page of the USF&WS to ascertain whether any changes had been made. Indeed they had. The single paragraph of "General Information" gives no indication that the newly named Fusarium torreyae is an exotic pathogen, and it is now portrayed as "a key contributor to the continued decline of this species." There is no indication that it is the sole contributor. Hence, one can surmise that the USF&WS has returned to its long-standing portrayal of environmental deterioration of the native range as the ultimate cause of pathogenicity.
Because reportage on the 2018 Torreya Symposium implies that University of Florida torreya involvement is on a fast-track for engineering disease-resistance into the Torreya genome, it is important to take a look at the foundational cause(s) of the context that opened the way for pathogens to become rapidly and severely lethal in the 1950s (and continuing today). For a quick review of the concept of nested levels of causation and their importance, visit this wikipedia page: "Proximate and ultimate causation".
Crucially, the 1986 Recovery Plan made clear the distinction between PROXIMATE and ULTIMATE cause(s):... The decline of Torreya taxifolia in its native habitat may ULTIMATELY be due to environmental factors that stressed the trees, including alteration of its forest habitat, alteration of vegetation above the ravines it inhabits, alteration of water seepage into the ravines, or droughts. The PROXIMATE causes of the decline are an assortment of fungal infections, resulting in stem cankers, stem and leaf blight, and possibly other problems (see p. 6). The decline has affected all wild Florida trees (Godfrey and Kurz 1962) and possibly all cultivated trees. (p. 2, emphases and caps added)2A. STEP BACK FROM "PROXIMATE" (DISEASE) CAUSE TO CONSIDER "ULTIMATE" (ENVIRONMENTAL) CAUSEAssuming that there is little or no scientific disagreement on Jason Smith's conclusion that Fusarium torreyae is the singular lethal agent now (and presumably during the 1950s as well), what caused this fusarium to become lethal? There are really only two possibilities for "ultimate cause":(1) Something may have shifted in the environmental conditions of Florida Torreya's tiny native range that assisted one or more pathogens and/or stressed the tree's defenses. Reference: "Anthropogenic Disturbances and the Emergence of Native Diseases: A Threat to Forest Health", 2022, Treena Burgess et al., Current Forestry Reports.Point (2) will be explored in depth before point (1).
(2) Perhaps a singular Fusarium species that was identified and established as lethal in 2011 is an exotic species that entered the Apalachicola region (perhaps from another continent) prior to the onset of Torreya population collapse.
2B. THERE IS NO SCIENTIFIC CONSENSUS THAT FUSARIUM TORREYAE IS AN EXOTIC SPECIESIt is true that several press reports in 2018 presented an exotic origin of this disease agent as fact (see below), but none of the peer-reviewed papers listed in 1D above (by Prof. Jason Smith) present the newly named Fusarium torreyae as exotic. Indeed, a cautionary note appears in the 2016 paper:
• "Two novel Fusarium species that cause canker disease of prickly ash (Zanthoxylum bungeanum) in northern China form a novel clade with Fusarium torreyae", by Zhou Xue, Kerry O'Donnell, Akayuki Aoki, Jason A. Smith, Matthe T. Kasson, Zhi-Min Cao, 2016, Mycologia.EXCERPT (emphasis added): ...Molecular clock estimates place the divergence of the FTOSC in the mid-Eocene , 40 Mya (O’Donnell et al. 2013), but it remains an open question whether this clade first evolved in the Old or New World. Furthermore, it remains to be determined whether F. torreyae is native to North America and restricted to T. taxifolia. Surveys for F. torreyae on Torreya endemic to China are warranted because it is the modern area of diversity of this genus (Li et al. 2001) and because the putative Asian origin of the CDZB pathogens could indicate that the most recent common ancestor of the FTOSC evolved in Asia....
NOTE: BARLOW has linked and excerpted all Fusarium torreyae papers here:
Recent Papers on Torreya Stem Canker Pathology.
Below are press reports or blogs that inaccurately present an exotic origin of the disease as factual:• "For Endangered Florida Tree, How Far to Go to Save a Species?", by Janet Marinelli, 27 March 2018, Yale Environment 360 (2,300 words)2C. IF THE PROXIMATE PATHOGEN IS NOT EXOTIC, THEN ULTIMATE CAUSATION SHIFTS TO ENVIRONMENTAL FACTORSEXCERPT: ... But in 2010, Jason Smith discovered the culprit, Fusarium torreyae, a fungal pathogen new to science. Evidence suggests that it was introduced from China....• "Saving the Torreya: Workshop Brings Scientists and Conservation Leaders Together", by Sarah Farmer, in USDA Southern Research Station, CompassLive, 8 May 2018.EXCERPT: ... The primary culprit appears to be a fungus called Fusarium torreyae. Jason Smith, an associate professor at the University of Florida, discovered the fungus in 2010. Scientists think the fungus is native to China....• "Saving the Endangered Torreya taxifolia", by Adam Black, article in March 2018 newsletter of Peckerwood Garden Conservation Foundation, multi-page illustrated report of his experience at the Torreya Symposium.EXCERPT: ... The fungus is thought to be introduced to the U.S. from overseas, considering how quickly it decimated the torreyas....
Indeed, the 2013 paper (Aoki et al.) that identified and named Fusarium torreyae (on which Jason Smith is a coauthor) put this disease agent in the context of environmental stresses long recognized:Aoki et al. 2013 EXCERPT: ... In addition to climate and other abiotic stresses, various biotic factors and anthropogenic activities have been implicated in the decline of this species. Added to these factors is a newly described canker disease of Florida torreya (hereafter abbreviated CDFT, Smith et al. 2011) caused by a novel species of Fusarium. Field surveys throughout its range in 2009 revealed that all dead and the vast majority of living Florida torreya trees exhibited signs of canker disease. Isolates of a Fusarium species recovered from cankers were used to successfully complete Koch’s postulates on cultivated Florida torreya, establishing that it was the casual agent of CDFT....Until the 2010s, a tremendous amount of thought (and some hypothesis testing) went into fleshing out possible environmental shifts that either elevated the virulence of native pathogens or degraded Torreya's disease defenses. The sense was that, if a shift in environmental conditions could be identified that correlated with the timing of population collapse, then remedial actions could be taken onsite to restore a healthy environment. Two lengthy technical reports may be the most complete online sources for learning the history of environmental hypotheses.
• "The Population Biology of Torreya taxifolia: Habitat Evaluation, Fire Ecology, and Genetic Variability", by Mark W. Schwartz and Sharon M. Hermann, 1992, Technical Report 1992(2) prepared for Florida Game and Freshwater Fish Commission, 108 pp. The table below lists 9 causal hypotheses, 7 of which are environmental. Note in particular the 9th hypothesis in the table, "Fungal Pathogens as an epiphenomenon." Clearly, that a proximate disease might have become lethal owing to environmental degradation was an early consideration.
See also: "Population Persistence in Florida Torreya: Comparing Modeled Projections of a Declining Coniferous Tree", by Mark W. Schwartz, Sharon M. Hermann, and Phillip J. Van Mantgem, Conservation Biology, 4 August 2000.
• "The Effects of Habitat Alterations on Growth and Vitality of Torreya taxifolia Arn. in Northern Florida, U.S.A: A Dendroecological Study", by Elizabeth A. Atchley, 2004, Master's Thesis, University of Tennessee (Knoxville), 118 pp. (Original research by Atchley centered on tree-ring analysis of downed Torreya logs, which are rot-resistant, and living pines.)EXCERPTS (emphases added): ABSTRACT. ... A master chronology extending back to 1869 was established using 125 pine cores. Twenty of the T. taxifolia cross sections were successfully dated, extending the chronology back to 1814. I found a significant positive relationship between growth and spring precipitation and an inverse relationship between growth and summer drought severity and summer temperature. The climate-growth response of T. taxifolia mirrored that of the pines, but was not as intense, possibly because of the protected understory habitat.2D. WHETHER THE FUSARIUM IS NATIVE OR EXOTIC, DO NORTHWARD PLANTINGS INDICATE DISEASE RESISTANCE?
The correlation between tree growth and precipitation suggests that moisture is the strongest determining factor of growth in this area. The inverse relationship with temperature illustrates the effect of higher temperatures on available moisture. A drought and warm period occurred simultaneously during the mid-1950s in combination with heightened clear-cutting practices and the construction of Woodruff Dam. It is my conclusion that habitat destruction occurring as early as the turn of the 20th century began weakening the Torreya. The unfavorable climate conditions and rapid degradation of the habitat that occurred during the mid-1950s further weakened the Torreya and allowed them to succumb to terminal infection by the blight.
Page 2: Some of the fungi possibly responsible for the blight are common natives that have never been serious problems in the past. There is now much speculation about multiple factors within the environment causing the decline of the T. taxifolia population. Several successive drought years that occurred in the mid-1950s were blamed for the initial decline, but this population is believed to have occupied the area since the last glacial period (Toops, 1981). A population established since then is likely to have survived more severe climatic shifts. Just prior to the decline of Torreya, part of the uplands above the Apalachicola bluffs were cleared and planted with slash pine (Nicholson, 1990). It is believed that the clearing of the area may have changed the hydrology of the ravines, or the reduction of canopy cover may have increased ambient temperature as more heat radiated off the unshaded soil. These factors could have weakened the trees to the point that they were more likely to exhibit pathologic symptoms of the fungus (Nicholson, 1990).
Page 12: It is also possible that current populations are climatic relicts that once had a more northerly range, but during the last glacial the advancing ice pushed them south where they mixed with the temperate deciduous forest species. It is possible that when the ice retreated, the Torreya did not reoccupy their northern range and could only survive in cool, moist refuges such as evergreen mountain forests, ravines, and some riverbanks. This is believed to be the case for Torreya taxifolia.
This is a key question that not only sidelines the disease genesis question. It suggests that assisted migration could be tested as an alternative to genetic engineering. Crucially, the answer may already be available, thanks to the presence of mature Florida Torreya specimens that were horticulturally planted in states northward of Georgia prior to species listing as endangered. Here is how to proceed:
(1) Access the HISTORIC GROVES annotated list on the Torreya Guardians website. Focus on the 90-year-old grove at Biltmore Gardens (Asheville, NC) and the century-old grove at Harbison House (Highlands, NC). See the photos, videos, stats, and learnings derived from each grove during site visits by Torreya Guardians. As you will see in the photos and videos, there is no macro indication that any specimens at these two sites are in disease-induced decline. The three upslope original plantings at the Biltmore that were exposed to sudden sunlight and topped when a pair of hurricanes felled the higher canopy white pines in their grove in September 2004 are neither thriving nor declining. Environmental deterioration is their main problem: Prolific basal sprouts appeared following the injury (as unlike genus Sequoia, genus Torreya does not repair top damage; instead it puts forth new stems via basals). Because these 3 trees abut the sidewalk, basal growth has been severely trimmed back by garden staff. Thus the trees are unable to repair and regrow in their customary way and they still lack canopy shade (on a south-facing slope). Meanwhile, at the Harbison House grove (which has deciduous canopy shade), there is no evidence of decline, although overly close placement of the specimens has generated differential access to sun and hence growth potential. Note: The original 1986 recovery plan for Torreya taxifolia (its first) contains this mention of the Biltmore trees:
(2) Test for whether Fusarium torreyae is present in either or both of these North Carolina mature, seed-producing groves (Biltmore and Highlands). Test both the originally planted trees and the naturally spawned saplings and seedlings nearby that were evidently dispersed from seed by squirrels.
(3) Evaluate results and consider next steps:(3a) If the pathogen is present, but nonlethal, then genetic engineering should not even be considered. Instead, the ideal way to free this endangered tree from its current glide toward extinction is assisted migration (see next section). Note: It is recommended that Prof. Jason Smith be queried on this matter, as it is possible that he has already sampled (and perhaps found) Fusarium torreyae in the Biltmore grove and with as-yet nonlethal consequences.NOVEMBER 2019 UPDATE: In November 2019 an audio interview with a primary institutional implementer of the Florida Torreya official recovery plan, JENNIFER CESKA (State Botanical Garden of Georgia), indicated that the fear of native conifer contamination in northward plantings (including official ex situ plantings in north Georgia) had ramped up to a level that "if we do see a problem, we would remove and burn that material." Ceska explained:
(3b) If the pathogen is not present in the two oldest North Carolina groves, the question turns to: What is the farthest northward extent the pathogen has reached and is it problematic there? Notably, is it on the grounds of Atlanta Botanical Garden or Callaway Gardens (southwest of Atlanta)? And has it established even farther northward in any of the ex situ plantings of Torreya in the northern region of Georgia (the southern-most Appalachian mountains). Overall, is there a sense that northward locations reduce or eliminate the destructive (even lethal) capabilities of Fusarium torreyae?
(3c) PROTOCOLS for plant translocations to guard against pathogen spread: Ideally, SEEDS (which are easy to de-flesh and purify in bleach water) are the ideal plant materials transferred from any source site to locale of final planting (hence the advantage of "freeplanting" seeds directly into their final forested habitat). If there is concern about pathogens migrating with the plants, protocols will need to be developed around branchlet cuttings and potted plants. Knowledge of the benefits of healthy symbiotic mycorrhizal partnerships has grown tremendously during the past 30 years. Even so, the 1986 recovery plan offered this cautionary note about the use of fungicides:... However, the coarse, thick roots of Torreya suggest that vesicular-arbuscular mycorrhizae may be very important to Torreya. Wide spectrum fungicides probably harm beneficial mycorrhizal fungi which could accentuate stress on the trees and further predispose them to fungal infection. (p. 11)"We thought we were taking the torreya away from the disease; we thought this was in the soil. We thought it could be introduced or always been there. Well, no. It's in the torreya; it is part of torreya. He named it; it's a fusarium named for torreya. It's in all of its tissues; it's passed from mother to child. And if the tree is healthy, everything's fine; they live together. But if the tree is weak in some way horticulturally, then this fusarium can express and it can spread. And in the lab Jason Smith has learned, he's done inoculations in the lab, that it can jump in the lab to different plant families."Meanwhile, Torreya Guardians posted a Historic Groves webpage that documents two century old plantings of Florida Torreya in the vicinity of Asheville and Highlands NC being not only disease-free but also regularly producing offspring that establish nearby (and with no human assistance). The other conifers in their surrounds express no pathologies (even though Fusarium torreyae has been documented by Jason Smith as present in the Biltmre torreyas). Links to the audio podcast of the Ceska interview and a transcript of key excerpts can be found in a November 2019 entry on the Torreya Guardians Reports webpage. For a lengthy argument on the importance of historic groves, see page 5 of the 26-page "Petition to Downlist Florida Torreya to Threatend" by Connie Barlow, September 2019.
2E. 2021-2022 - SCIENTISTS CONCLUDE THAT POLEWARD PLANTINGS DO ENABLE TORREYA TO LIVE ASYMPTOMATICALLY WITH FUSARIUM; ARGUMENT TO "KEEP" TORREYA IN NATIVE RANGE SHIFTS TO FEAR THAT OTHER TREE SPECIES MIGHT BE HARMED IF FUSARIUM SPREADS.
NOVEMBER 2021: "The Endangered Florida Torreya", November 2021, by Lilly Anderson-Messec, for Tallahassee Democrat. Key excerpts confirming that Fusarium torreyae, while present, do not exhibit disease symptoms when Torreya trees are "not stressed" and that northward plantings seem to evoke the tree's resistance to this canker-causing fungus:... So, what is killing the Florida Torreya? The reasons for its decline have been hotly debated, though habitat degradation due to development, silviculture, climate changes, and other human causes have all contributed. The trees are also susceptible to damage by deer rubbing. Over the years, many hypotheses have been proposed for the disappearance of Torreya, however, the primary culprit of the death and decline of this species was named in 2011: Fusarium torreyae.
This fungal pathogen was unknown to science until recently identified and described by Dr. Jason Smith at the University of Florida. Jason suspects this fungus evolved in Asia along with relatives of Torreya taxifolia native to that region and was likely introduced through the import of those non-native species for horticultural uses, though more work will be needed to know for sure. This is just one example of how we "roll the dice" ecologically when we import and plant non-native plants. The plants you add or remove from your yard can have devastating effects on our ecosystems. Choosing native plants is always the best option.
When the trees are stressed, the fungus causes leaf blight and stem cankers, ultimately killing it back down to the roots or killing the plant entirely. The tree may resprout but remains infected and will repeat this process. Trees can be infected without showing any signs of disease but may begin to show signs if stressed. All Torreya taxifolia trees tested have been infected with the fungus, so even if they don't show signs of disease, it is probable that all plant material of this species is infected...." Lilly Anderson-Messec is the Director of North Florida Programs for the Florida Native Plant Society (FNPS), the Director of the FNPS TorreyaKeepers Project, and a volunteer writer for UF/IFAS Extension Leon County, an Equal Opportunity Institution.
MARCH 2022, a webinar was posted on youtube titled, "Endemic and Endangered: The Plight of the Florida Torreya" by Lilly Anderson-Messec, Feb 2022. Anderson-Messec is a staff person of the Florida Native Plant Society whose works centers on northern Florida plants and thus supports the "Torreya Keepers" subgroup of the society, which formed just prior to Hurricane Michael and which garnered funds from FEMA to support a staff person following the hurricane. Mission: "The purpose of TorreyaKeepers is to assist in recovery of the Florida Torreya tree in its native range by conducting citizen science and outreach to private landowners in support of the federal recovery plan and to provide local support to efforts for recovery partners."
ABOVE: At timecode 21:00, Anderson-Messec describes Florida Torreya as "functionally extinct" in its native range, and describes the reasons for its decline as being "hotly debated." Then, at 23:18 she says "the primary culprit of the death and decline of this species is due to another reason: Fusarium torreyae ... Jason [Smith] suspects that this fungus evolved in Asia along with relatives of Torreya taxifolia native to that region and was likely introduced through the import of non-native species for horticultural uses although it's very difficult to know for sure.... The trees can look healthy, and especially planted specimens tend to look and grow very healthy, until for some reason they are stressed... The trees can have no symptoms of the fusarium but still be infected.... It is suspected that all known materials of this species is infected with this fusarium.... Most worryingly, this fusarium (which is spread by airborne spores) has been shown to infect unrelated hardwood species as well as other rare conifers such as Carolina hemlocks, Eastern hemlocks, and other Pinus species. So, for this reason, it is not recommended to plant Torreya taxifolia outside of its narrow native range, to avoid unforeseen consequences of spreading this fungal pathogen."
ABOVE: At timecode 28:20, Anderson-Messec states, "So, again, the most important thing you can get from this talk is not to plant Torreya outside of its native range. So, Dr. Jason Smith at the University of Florida has been doing extensive trials on this fusarium, and he has done many experiments inoculating other genera with this fusarium, and it definitely infects and kills other species.... The most susceptible to the fusarium was actually Pinus pungens, which is the photo in the lower right. In just 4 weeks, post inoculation with the fungus, it killed the tree. And it negatively affected the health of pretty much all the trees he tested it on, with the exception of one of the torreyas that occurs in China."
During the Q&A session of this webinar, at timecode 58:13, a Torreya Guardian planter in Ohio has his question read from the chat: "I have 4 trees planted in 2007 before the discovery of the fusarium. Are Torreya Keepers suggesting these trees be removed?"
Anderson-Messec answers, "We're not suggesting that. No. Planted trees are much less likely to show signs of infection. And also they're less likely to spread infection, if they're not showing signs, because the fungus needs to create spores and grow. So if you aren't seeing signs of the fungus on your torreya, then it is likely considered to be still infected but it is less likely to spread that infection if it is not showing outward signs.... We're not suggesting anybody should remove them. We're just suggesting that planting them outside of its native range is putting other species at risk."
Immediately following the webinar, CONNIE BARLOW wrote a lengthy email to USDA forest pathologist, Tyler Dreaden, who is lead author of "Detection method for Fusarium torreyae the canker pathogen of the critically endangered Florida torreya, Torreya taxifolia", by Tyler J. Dreaden, Tania Quesada, Jason A. Smith, 2020, Forest Pathology. Barlow's email to Dreaden is posted. Her final paragraph is this:CONNIE BARLOW concluded her correspondence: As I expressed in my previous email to you about your 2020 paper, I have great skepticism about the relevance of inoculations of Appalachian tree species in potted laboratory settings and presumably with no exposure to annual winter conditions of freezing, as occurs in the Appalachian region and northward. At minimum, I hope your forthcoming paper clarifies that detection of the Fusarium on an outdoor northward-planted Torreya specimen that does not exhibit symptoms of the disease, does not pose a risk to other tree species. Ideally, I hope your forthcoming paper also specifies the methodology of inoculation and the timing and conditions of the lab testing, so that the ecological relevance of the results can be evaluated by other pathologists and ecologists.
ABOVE: Spring 2022, Barlow encountered several papers that exemplify the broad scholarship dealing with many species of genus FUSARIUM (both exotic and native species) that are regarded as pests of conifer species planted in tree farms for economic uses:• "Management of Fusarium Diseases Affecting Conifers" EXCERPTS: "Indications that co-occurring microbes can have suppressive effects on pathogens affecting conifer seedlings follow from the observation that although decline and death of seedlings induced by F. oxysporum is common in nurseries, disease caused by this fungus is not a problem in coniferous forest soils covered with needle litter. Smith (1967) noted whereas F. oxysporum was recovered from the roots of 90% of sugar pines when trees were lifted from nursery soil, this fungus was not detectable on roots of sugar pines four years after outplanting in the forest.... F. oxysporum is rarely recovered from forest soils.... Predictions of the model were consistent with the distribution of pitch canker in North America, where the disease has been established long enough to have approached ecological limits on its geographic range.Barlow was grateful to encounter these papers because they suggest that natural conditions in forest soils, in healthy climates, seem to discourage development of fusarium infestations into pathogenic outbreaks. Instead, the fact that tree farms rely on planting of nursery-grown stock and that fumigation (which may also destroy mycorrhizal symbiotic fungi) has regularly been applied by nurseries but may be disallowed in the USA, substantiates that the care taken by both free-planting and potted seedling techniques within Torreya Guardians for ensuring healthy, symbiont-rich soil conditions reduces the prospect of fusarium diseases. As well, the group deliberately plants Torreya substantially poleward of peak-glacial range and thus in climates less conducive to Fusarium outbreaks.
• "A Global Climatic Risk Assessment of Pitch Canker Disease" The map at upper right is drawn from this paper, and it demonstrates that, with respect to a now-global pest of tree farms, Fusarium circinatum, is clearly blocked by cooler climates. As well, the paper states, "Likewise, Chile, which is known to have Fusarium circinatum in the nurseries but not in the plantation forests, was also predicted to have marginal to suitable climatic conditions for pitch canker establishment. Regions of China, Brazil, Australia, and New Zealand were predicted to have optimal climate conditions for disease establishment."
• "Management of Fusarium diseases affecting conifers". This paper offers (1) helpful background on understanding the importance of environmental conditions in determining whether a Fusarium pitch canker or root disease will show injurious symptoms, (2) the difficulties in any attempt to prevent Fusarium species from spreading, (3) methods that determined that F. circinatum, which currently causes pitch canker problems in the USA probably was native to Mexico, spreading into various places in the USA via commercial nursery trade. F. torreyae is mentioned in this 2015 paper as being too recently discovered to have a knowledge base appropriate for treatment in this genus-level paper.
• "Fusarium species associated with plants in Australia". Although within the geographic context of Australia, this paper also includes "cosmopolitan" species some attributing, at least in part, the wide distribution to the global trade in plant materials; others implying that multi-continental distribution may be caused by natural airborne distribution of propagules. One also learns in this lengthy paper that many Fusarium species manifest disease symptoms in plantation forestry of globally grown conifer species only in particular climates. As well, within the believed native ranges of a Fusarium species, disease symptoms on conifers may appear in regions where that Fusarium is found in native grasses but exhibiting "asymptomatic" and "commensal" (thus non-problematic) behavior in those grass species. In such circumstances, one cannot expect to eliminate from conifer plantations disease outbreaks that carry forward commensally in native grasses.
A rereading of the Australia paper in December 2022 helped Barlow understand that recent assertions that Fusarium torreyae can be found "in all plant materials" of Florida Torreya (including the internal tissues of seeds) is not unexpected. These would be "endophytic" occurrences of Fusarium, which only manifest in disease problems when the plant is "stressed." Importantly, endophytic occurrences within SEEDS are problematic mainly when trade would deliver seeds into climatic zones where the Fusarium would manifest disease symptoms in the developing seedling. Accordingly symptomless endophytic" pathogens, including fungal species, were reported in the 2010 Recovery Plan Update (p. 5; excerpted at length in item 1E above). Key passage:Identify pathogen(s) responsible for the decline: This is an ongoing action that goes back to 1967 (Alfieri et al. 1967). The authors observed that the stem and needle blight disease of T. taxifolia appears to be incited by a fungus causal agent implicating Physalospora and Macrophoma. Alfieri et al. (1987) isolated six other fungi from leaves and stems of T. taxifolia. Lee et al. (1995) isolated more than 30 different endophytic fungi, but consistently, Pestalotiopsis microspora (a fungus that resides in the inner bark of symptomless T. taxifolia trees) was found on diseased trees. They concluded that the pathological activity of this fungus could be triggered by physiological and/or environmental stress.A U.S. Fish & Wildlife Service scientist engaged in direct study of Torreya taxifolia pathogens herself, and coauthored a book chapter that reported results in 2013. A lengthy quote from that report appears in item 1E above). There you will find mention of the history of Fusarium species documented in the wild specimens (including F. lateritium), the prior inability to single out a single pathogen as cause of stem dieback, and initial attempts to utilize DNA analysis to situate Fusarium pathogens into known clades.
A short, 2022 paper titled "Root Rot Disease of Torreya grandis Caused by Fusarium fujikuroi in China" was notable for concluding, via sophisticated genetic testing, that "this is the first report of F. fujikuroi causing root rot of Torreya grandis in China." The paper was also notable for stating, "Its fruit is a precious nut in China, rich in vitamins and minerals, can be directly eaten, can also be used as medicinal plants with functions of lowering blood lipids and softening blood vessels."
2F. EXPERIENCE VISUALS OF THE NATIVE TORREYA HABITAT AND DISEASE SYMPTOMS• VIDEO: Site Visits to Florida's Endangered Torreya and Yew Trees
Connie Barlow presents 15 years of baseline photos and videos she recorded of Torreya taxifolia and Taxus floridana in their historically native range in Torreya State Park in northern Florida. Photos of spectacular California Torreya trees, recorded by Barlow in 2005, show the potential for Florida Torreya recovery efforts to strive for. Fred Bess shows (in 2014 video) 2 Asian conifers (Cephalotaxus and Cunninghamia) used in landscaping that are Torreya look-alikes. Paleoecological evidence that Florida's Torreya was "left behind" in its peak glacial refuge supports "assisted migration" actions.
2G. TEST FOR DISEASES IN WILD GROVES OF CALIFORNIA TORREYA
In 2005 I (Connie Barlow) visited wild groves of Torreya californica primarily to gain personal experience in ascertaining where, how, and structurally this genus grows in its native mountainous range. Although I did document one large tree dying in a built area, I did not look for, nor perceive, leaf- or stem-killing diseases. Photos below are (left to right) a fog-laden creek canyon just north of Santa Cruz (Scott's Creek); Sequoia King's Canyon National Park; coast range NW of Napa Valley. Access photo essays of all California sites visited in 2005. A serious deficit in the official actions for Florida Torreya recovery (Atlanta Botanical Garden, State Botanical Garden of Georgia, University of Florida) throughout the decades following the 1986 recovery plan is that only Torreya Guardians has paid any attention to what the California congeneric can teach us for discerning preferred habitats during these peak interglacial (and beyond) times.
DETAILS OF ABOVE CALIFORNIA PHOTOS: (1) Left - The biggest wild specimens are all near the foggy coast just north of Santa Cruz. Scott's Creek torreyas may have benefited from the 1806 San Francisco earthquake/fire, which stimulated logging of the overstory Coast Redwoods for rebuilding. The subcanopy torreyas would have been released into sunlight, with champions now approaching 200 feet in height. (2) Middle - Connie stands on a very steep slope with a common form of mature torreya: 2 or 3 stems sprouting from presumably the same root crown. Right foreground are torreya saplings and seedlings. Because the species is rare, but locally abundant wherever it is found, a dispersal problem for its large seed is the likely cause. (3) Right - Towering Redwoods and Douglas-fir consign Torreyas to horizontal growth, with main stems leaning with branches then rising vertically in quest of snatches of sunlight. Seedling in the foreground is lit by camera flash, as midday is very dark on this steep ravine wall.
TORREYA VIDEO 23: Florida Torreya's California Cousin Has Clues for Ex Situ Plantings
In 2005, Connie Barlow visited 4 forested regions in California where Torreya californica could be found growing in the wild. Her aim was to experience and photo-record observations of the trees and their surrounds such that volunteer planters of the Torreya species native to the eastern USA (along with professionals in charge of this endangered species' recovery) could discern habitat preferences of the genus and thus pinpoint similar environments in eastern states for planting seeds and seedlings. Read Connie's 2005 observational notes at: Photo-essays of California Torreyas.
WHY DISEASE TESTING OF CALIFORNIA TORREYA MATTERS: If the same Fusarium stem-canker is present in one or more wild Torreya californica groves but it is not lethal, then either disease-resistant genetics or better peak-interglacial habitat could be the cause, and further experimentation would be warranted.
Part 3. Assisted Migration of Glacial Relicts, Not Genetic Engineering
3A. APALACHICOLA AS GLACIAL REFUGIUM AND TORREYA AS GLACIAL RELICT ARE UNDISPUTED
Until 2021 it was undisputed that the Apalachicola area (within which is Torreya State Park) is a glacial refugium and that Torreya taxifolia is a glacial relict. The 2010 recovery plan, the original (1986) recovery plan, the (1984) listing in the Federal Register of Florida Torreya as an endangered species, and the original Draft Environmental Impact Statement all mention the refugial nature of the habitat and the relictual ecological status of the tree (see items below). First, a look at the limits of the decision-process that guided the agency's response to the Downlisting Petition.
• 2021 U.S. Fish & Wildlife Service "DECISION" on the "Petition to Downlist". (The downlist petition itself was filed September 2019 by Connie Barlow.)EXCERPT: "... the petition has not provided substantial evidence that would lead a reasonable person to believe that the historical range of T. taxifolia is larger than described at the time the species was listed (Factor A). The petition cited our 1986 Recovery Plan and 2010 5-year review in support of the position that the historical range is larger than described at the time of listing. However, while we acknowledge that the 1986 Recovery Plan and the Service's 2010 5-year review speculate that the geographical range of T. taxifolia, or presumably an ancestral species (i.e. T. antigua), may have, in past geological times, included localities as far north as North Carolina, no native trees have been documented outside of the species' defined current or historical range, and both the Service's 2010 5-year review and the 1986 Recovery Plan confirm that all known native populations occur within four counties in Florida and Georgia."Editor's note: Just as the USF&WS policy is not open to considering future range shifts forced by climate change, this document evidences that whether or not the species is a glacial relict, the only geographic focus for recovery is the established "historic range." Sadly, whether or not the species arrived at its present endemic range as a result of glacial advance and cooling is not a matter for discerning the boundaries of geographic locale that will be the sole focus for 'habitat amelioration." This is a significant departure from the early days of ESA recovery planning, when "glacial relict" status was deemed important for discerning how best to serve a listed species. And given 21st century rapid climate change, the confines of restoration merely to "historic range" become even more out of sync with reality dooming the species to a future life, in any, merely of permanent "safeguarding" rather than a wild, forest future.
• (undated) Draft Environmental Impact Statement - "... the bluffs and ravines served as a refugium when northern species migrated southward during glacial times and today the area has a high rate of endemism and unique vegetation."
• 1984 Federal Register. EXCERPTS: The Service determines Torreya taxifolia (Florida torreya) to be an endangered species pursuant to the Endangered Species Act. This plant is endemic to the Apalachicola River area in Florida and Georgia. It is endangered by a fungal disease, which kills trees before they reach seed-bearing size.... An evergreen tree reaching 18 meters tall, Torreya taxifolia (Florida torreya) was first discovered in 1834 and formally described in 1838. The Florida torreya and other endemics of the Apalachicola River system have received much attention from scientists and local residents. The relictual nature of this area accounts for the presence of many unique species (James, 1967). During recent glaciations, species migrated southward by way of the Apalachicola River system, which served as a refugium during cooling periods. The Apalachicola River is the only Deep River system that has its headwaters in the southern Appalachian Mountains. With the receding of the glaciers, cool moist conditions persisted on the bluffs and ravines of the Apalachicola River after climatic change rendered the surrounding area much drier and warmer. The entire Apalachicola River bluff system today is an extremely diverse and unique ecosystem, of which Torreya taxifolia is a part. ... All mature viable trees are located in botanical gardens and arboreta. The wild trees do not now have good long-term survival prospects. The initial focus of recovery will be to address controlling the disease. After the disease has been overcome, recovery efforts would address reintroduction of the species into the wild."
• 1986 "Florida Torreya Recovery Plan", U.S. Fish & Wildlife Service - EXCERPTS: Torreya is a genus of four or five species from Florida and Georgia, California, China, and Japan. The present geographic distribution of the genus is similar to the distributions of several other plant genera. The distributions, together with fossil evidence, suggest that these genera had wide distributions during the Tertiary Period that were subsequently reduced by climatic changes during the Quaternary (James 1961, Delcourt and Delcourt 1975).... The decline of Torreya taxifolia in its native habitat may ultimately be due to environmental factors that stressed the trees, including alteration of its forest habitat, alteration of vegetation above the ravines it inhabits, alteration of water seepage into the ravines, or droughts. The proximate causes of the decline are an assortment of fungal infections, resulting in stem cankers, stem and leaf blight, and possibly other problems (see p. 6). The decline has affected all wild Florida trees (Godfrey and Kurz 1962) and possibly all cultivated trees.... The species may be restricted to the area because it failed to migrate northward at the end of the Pleistocene.
• 2010 "Torreya taxifolia (Florida Torreya) 5-Year Review: Summary and Evaluation", U.S. Fish & Wildlife Service - "... Based on fossil records, we can speculate that the geographical range of T. taxifolia included North Carolina and perhaps, it was forced south by glaciers, and when they retreated, it became isolated in small areas of the southeastern United States." (p. 12)
Source: "Phylogenetic Relationships of Torreya (Taxaceae)
Inferred from Sequences of Nuclear Ribosomal DNA ITS Region",
by Jianhua Li et al., 2001, Harvard Papers in Botany.
TWO BOTANY PAPERS IN 1905 PORTRAY TORREYA AS A GLACIAL RELICT:
• 1905 - "A Remarkable Colony of Northern Plants Along the Apalachicola River, Florida, and Its Significance" - by H. C. Cowles, in Report of the Eighth International Geographic Congress Held in the United StatesRECENT REVIEW PAPER IN JOURNAL OF BOTANY FEATURES TORREYA TAXIFOLIA AS EXAMPLE OF "MIGRATIONAL LAG":EXCERPT: ... In this association one finds two of our most notable endemic plants Torreya and Croomia. It seems likely, then that we should regard Torreya taxifolia as a northern mesophytic left stranded to-day only in Florida. It presumably is one of the plants that failed to follow up the last retreat of the Pleistocene ice, and is preserved here perhaps because of exceptionally favorable topographic conditions.
• 1905 - "Gameotophytes and Embryo of Torreya taxifolia", by John M. Coulter and W.J.G. Land, pp. 161-62 in Botanical GazetteEXCERPT: ... It is associated with a remarkable and somewhat extensive group of northern mesophytic plants, and the conclusion is irresistible that Torreya is a northern plant of the most pronounced mesophytic tendencies, and to be associated with such forms as the beech-maple-hemlock forms of our northern woods, our most mesophytic type of association."... Torreya taxifolia Arn. has experienced, range-wide decline, which may be due to lagged responses to climate change (Barlow and Martin, 2005)." "Disequilibrium Vegetation Dynamics Under Future Climate Change", by Jens-Christian Svenning and Brody Sandel, 2013, American Journal of Botany, "Special Invited Article."RECENT MAGAZINE ARTICLES PORTRAYING TORREYA AS A GLACIAL RELICT:
• 2007 - "The Florida Torreya and the Atlanta Botanical Garden", by David Ruland, in Conifer Quarterly, pp. 10-14. Note: As of 2019, David Ruland is Greenhouse Manager for Atlanta Botanical Garden.3B. PUBLICATIONS POST-LISTING (ENDANGERED SPECIES) LACK ASSISTED MIGRATION DISCUSSIONEXCERPT: ... According to fossil records, the Florida torreya is estimated to be over 165 million years old. Like many other conifers with such an impressive age, it was once scattered throughout the northern hemisphere. Scientists theorize the species was driven south by glaciers that once covered the northern latitudes. When the glaciers retreated, the Florida torreya was left isolated in small microhabitats of the southeastern United States, where it thrived for thousands of years. ... The Florida torreya is a glacial relic, seemingly stranded in an increasingly hostile niche without any natural means of escape or survival. This tree would certainly be doomed without the intercession of concerned individuals and institutions....• 2017 - "Steephead Salamander Search, and the Apalachicola's Ice Age Refugees", by Rob Diaz de Villegas, WFSU Ecology Blog, 16 November 2017 (contains many excellent photos)EXCERPTS: ... If you go back millions of years, before the ravines that you see are in place, you would have had a relatively large, flat, sandy plateau," says David Printiss. Printiss is The Nature Conservancy's north Florida program manager, overseeing the Conservancy's Apalachicola Bluffs and Ravines Preserve. "During the last glaciation," says David Printiss, "all species from the Appalachians were pushed southwards by the cold weather." These changes occurred over thousands of years, so everything from large tree species to little salamanders would shift their ranges as temperatures changed. When these Appalachian species found steep, narrow ravines with cool, flowing water, it felt like home. So when temperatures got warmer again, many northern plants and animals left behind small populations in ravines and slope forests. Some entire species remained here, and only here. And so we have an interesting mix of flora and fauna that makes steepheads unique. "We have the southern end of the distribution of species like mountain laurel that you wouldn't expect," says David Printiss. "And you have other species that you'd call glacial relicts. They were left behind, so their sister species are up in the Appalachians.... There are other [relict] species like the torreya tree that just simply could not run uphill fast enough and was left behind," says Printiss. "So its global distribution is Torreya State Park and the Apalachicola Bluffs and Ravines Preserve."
The 1986 recovery plan, p. 8, confines the geographical goal: "(3) ... investigate the decline to determine its cause, and, if possible, to find a cure; and (4) introduce cultivated plants into secure habitat within its former range."
Written records accessible online fail to indicate any intent (not even curiosity) about thwarting the lethal disease(s) by moving Torreya northward to cooler climes. Rather, discovery of a curative approach culminating in "reintroduction" to its currently native range was the only desired outcome set forth. A popular article published in 1990 and written by one of the scientists who participated in the official collection and rooting of branchlets from the remaining wild trees failed to mention that establishing northward sites might be helpful even while pointing to "global warming" as a possible cause:
• Chasing Ghosts: The steep ravines along Florida's Apalachicola River hide the last survivors of a dying species, Torreya taxifolia, by Rob Nicholson, 1990, Natural History MagazineEXCERPTS: ... All the unknowns confound any recovery plan. Is Torreya an early victim of global warming and a precursor of a new wave of inexplicable extinctions? Has local land use destroyed this Torreya habitat? Is there any point in trying to fortify existing populations by replanting if a virulent pathogen lurks unchecked? Will propagations of cuttings from existing wild trees carry a new pathogen wherever the new trees are distributed? Or, frozen by doubt, will plant scientists do nothing while the unique species slips away, tree by tree?• CLASSIC BOTANY PAPERS are excerpted in a special section toward the bottom of this webpage. Two 1905 papers (one by John Coulter and the other by H. C. Cowles) identify Torreya taxifolia as a glacial relict. Their proclamations were preceded decades earlier by none other than Asa Gray.
... The Apalachicola Bluffs and the ravines that dissect them are at the cusp of the deciduous woodlands and the lush subtropical jungle. It is an undecided forest, its luxuriant ecotone having been shaped by the forces of glaciation during the Pleistocene era. As a New Englander used to deciduous woods, I was unsettled by seeing beech, maple, and hickory mixed with bold fan-leafed palmettos, spiky yuccas, and huge evergreen magnolias.
"... In June 1989 I joined Mark Schwartz and we surveyed as many ravine systems as possible, carefully mapping and labeling the plants growing there.... When we returned in the fall, we collected small cuttings, tissue samples, and soil samples for genetic, propagation, and pathological studies. Alarmingly, in just a few months, a number of our mapped trees had been lost to deer rubbing, disease, and even falling limbs from the upper canopy. The species was going extinct before our eyes and will probably not last another generation.
... More than 2,500 cuttings were collected from 166 trees and were treated with a variety of hormones to promote rooting. These were brought to Harvard's Arnold Arboretum, where 2,100 were successfully rooted and potted. The accession number of the sampled trees follows each of these clones (and any subsequent propagations) with the particulars as to the plant's original location in the wild. Therefore, in the distant future, ravines might be replanted with the same genetic material that once grew there. Cuttings taken from the wild five years ago are growing well and so far show no signs of disease.
... While the few remaining saplings may outlast the blight, not many people who have seen the trees would wager their homes on it. More likely, clusters of trees, propagated from specific ravines, will be grown in botanical gardens, universities, preserves, and state parks. This Florida native, as evidenced by the few healthy trees in cultivation, seems to thrive on the southern slopes of the Appalachian Mountains and is more cold tolerant than its present range would suggest. Possibly an Apalchicola refugium can be re-created, an artificial Torreya forest where pollen can float, genes mingle, and the evolution of the past hundred million years can continue, even if it is in a pitifully discounted format.
, 2018, prepared for USDA Forest Service Climate Change Resource Center
3C. EARLY ADVOCACY OF ASSISTED MIGRATION BEGINS WITH BILL ALEXANDER AND CONNIE BARLOW
CONNIE BARLOW WRITES: I am founder of Torreya Guardians, and I am documented as having advocated for assisting Florida Torreya to migrate northward, beginning in 2001:
• The Ghosts of Evolution: Nonsensical Fruit, Missing Partners, and Other Ecological Anachronisms, by Connie Barlow, 2001 (Basic Books)
EXCERPT: ... In a study of endangered species published in 2000, Rob Channell and Mark Lomolino concluded that "most species examined persist in the periphery of their historical geographic ranges." The implication is that the last place a troubled species is found may not, in fact, be the best place to assist its recovery. Transplantation is an uncommon and controversial technique for biodiversity conservation today. But after the greenhouse effect has ratcheted up temperatures and rerouted rainfall, it surely will become the norm. If gardening a few local patches of endangered plants is tough today, it's going to get a lot tougher when, like it or not, we become gardeners of the planet. Helping plants track climate change from one patch of forest to another will be a routine tactic for conserving biodiversity decades hence. Is it too early to begin now with Florida torreya?
Note: My 1999 visit to Torreya State Park and subsequent ruminations appear on pages 229-231.
Later, I learned there had been an advocate for northward movement of Torreya before me. In late February 2004 I visited the Biltmore Estate and Garden near Asheville NC for the first time. There I met with Bill Alexander in his office before he showed me the otherwise unmarked site where Florida Torreya had been growing and naturalizing. Bill told me that he had advocated (alas, to no avail) at a conference in the 1990s for assisting the recovery of Torreya taxifolia by planting more specimens in northward locales. I documented that conversation in a chapter I contributed to a 2009 book, published by MIT Press.
• Chapter 10, "Deep Time Lags: Lessons from Pleistocene Ecology", by Connie Barlow:• Next, in 2004 CONNIE BARLOW and Pleistocene ecologist PAUL S. MARTIN co-authored an advocacy essay:
... One section of [my 2001 Ghosts of Evolution] book used the deep-time perspective to re-examine the circumstances of perhaps the world's most endangered species of conifer tree: the Florida torreya (Torreya taxifolia). It occurred to me that torreya's desperate plight owed to its failure to migrate north (perhaps for want of a seed disperser) from its Ice Age refuge in the Florida panhandle to habitat better suited to the tree's needs in peak interglacial times. That better habitat would likely have been the core of torreya's range during previous interglacials: the southern and central Appalachian Mountains.
As it turns out, I was not the first to make this suggestion. Bill Alexander, forest historian at the Biltmore Gardens of Asheville, North Carolina (in the central Appalachian Mountains), observed his garden's own grove of Florida torreya, and concluded that North Carolina seemed more conducive to the wellbeing of this conifer than was northern Florida (personal communication)...
EXCERPT CONTINUES: In a 1990 article, botanist Rob Nicholson speculated, "Is Torreya an early victim of global warming and a precursor of a new wave of inexplicable extinctions?" How prescient he was! Thanks to a host of recent scientific papers (e.g., Barlow and Martin 2005; McLachlan et al. 2007; Hoegh-Guldberg 2008) and popular articles (e.g., Fox 2007; Nijhuis 2008; Marris 2008), Florida torreya has become a "poster plant" for alerting the public and scientists alike to the lurking dangers of global warming and to the consequent need for what has come to be known as assisted migration. Assisted migration must not, of course, be promoted as an alternative to reducing greenhouse gas emissions. But it is decidedly unrealistic to assume that climatic change and its challenges to biotic diversity will vanish in the next decade or two. Again, time lags (melting polar and glacial ice) will take a long time to equilibrate even if the concentration of atmospheric CO2 could politically and economically be stabilized at today's levels....
ABOVE: Wild Earth journal published a "Forum" pair of essays in its Winter 2004/2005 issue. Access in pdf the PRO Assisted Migration article by Connie Barlow and Paul S. Martin. Also, the ANTI Assisted Migration article by Mark Schwartz.
BACKGROUND ON THE ABOVE "FORUM" ARTICLES. Barlow initiated extensive communications with professional botanists and others in 2003-2004, hoping to work through issues and find common ground for joint publication of a journal article in favor of assisted migration for Florida Torreya. Discussions were helpful but ultimately failed to reach any consensus. Barlow and Paul S. Martin held the most radical position, so they stepped ahead with writing an article, and then recommended that Mark Schwartz would be the professional most suited for (and interested in) contributing an oppositional piece. More detail, along with links to archival documentation of communications can be accessed at Archived Documents of Early Roots of Torreya Guardians. An excerpt is below:• CONNIE BARLOW has a peer-reviewed chapter in a 2009 book that advocates in behalf of Florida Torreya. (This book was already referenced above as documenting Bill Alexander's advocacy. Here it appears in chronological sequence to affirm Barlow's published advocacy.)
March 24, 2004 - title: Torreya: 10 questions for discussion
Hello Torreya Group: This is Connie Barlow. I am dedicating today to Torreya taxifolia, as I need to catch up with you all with thoughts and conversations that have come my way over the past few weeks, and which only now I am having a chance to assimilate and pass on. Bascially, since I last wrote to you in depth, I have visited the T. taxifolia propagation effort at Atlanta Botanical Garden (Ron Determann and Carol Denhoff), the thriving grove of T. taxifolia at the Biltmore Gardens in Asheville (Bill Alexander), the office of Hazel and Paul Delcourt at University of Tennessee Knoxville (from which I walked off with a lot of useful papers to read and a lot of sobering thoughts), and a potential private preserve for rewilding T. tax along the east side of the Cumberland Plateau.
....[final para] This realm of thought is very depressing for me, because I am a wildlands advocate and would vastly prefer us to simply make preserves big enough and corridors connected enough for nature to do what it needs to do without our meddling. The Fall issue of Wild Earth is on the theme of corridors, so what sorts of contributions might be generated from this group, from our discussion of T. taxifolia and all the ancillary thoughts that go along with that?
"Deep Time Lags: Lessons from Pleistocene Ecology"
by Connie Barlow, 2009, (9 pp. pdf)
Eileen Crist and Brruce Rinker, eds., MIT Press
EXCERPTS CONTINUE (that focus on "assisted migration" as a new tool in conservation biology): ... Assisted migration as a conservation tool is both fascinating and frightening for anyone focused on plants. It is fascinating because endangered plants can be planted by whomever so chooses, with no governmental oversight or prohibitions—provided that private seed stock is available and that one or more private landowners volunteer suitable acreage toward this end. This cheap-and-easy route for helping imperiled plants is in stark contrast to the high-profile, high-cost, and governmentally complicated range recovery programs for mobile animals, like gray wolf, lynx, and California condor.
&nbps; Assisted migration frightens for precisely the same reasons it fascinates: anybody can do it, for good or ill, and with care or abandon. Its promotion could undermine decades of public education about the dangers of nonnative plants, as well as more recent efforts to promote the concept of wildlands corridors and connectivity. Still, in an age of deforestation, severe habitat fragmentation, and rapid global warming, assisted migration as a plant conservation tool should not be ignored. According to Peter Wharton, curator of the Asian Garden of the University of British Columbia Botanical Garden writes, "... the Torreya question is a door to immense issues relating to how we facilitate global 'floraforming' of vegetational zones in a warming world. It represents another layer of responsibility for those of us who have a passion for forests and wish to promote the ecologically sensitive reforestation of so many degraded forest ecosystems worldwide" (P. Wharton, personal communication).
The test case for assisted migration occurred in July 2008 when the citizen group I helped found (Torreya Guardians) undertook assisted migration for 31 seedlings of Torreya taxifolia purchased from a nursery in South Carolina. A handful of volunteers (and reporters documenting the action) gathered in the mountains near Waynesville, North Carolina, to spend a day planting the seedlings into wild forested settings on two parcels of private land. The Torreya Guardians' website documents that action....
Torreya taxifolia is a Case Study in Conservation Biology
ENDANGERED SPECIES PROTECTION OF PLANTS V. ANIMALS: A 1988 paper published in Pace Environmental Law Review offers an excellent history of the long-held distinction in U.S. governmental regulation of plants v. animals ("wildlife") and how that distinction was forged into a compromise that entailed less rigid regulation (and to some extent, entire "exceptions") for how plants would be handled under the 1973 Endangered Species Act. See in pdf the 1988 article by Faith Campbell, "Legal Protection of Plants in the United States", which is also a reference for the PLANTS paragraph in the ESA 1973 wikipedia entry.
A visit to the Annotated Scholarly Links webpage on this website reveals that the controversy over assisted migration of Florida Torreya, (and the fact that citizens have stepped out ahead of official managers of this listed endangered species) has garnered a lot of attention within both the conservation biology and forestry professions.
The MEDIA have also given this controversy a great deal of attention. On the History of Torreya Guardians webpage one can learn about these citizen actions and also access a linked and excerpted list of Torreya Guardians in the Media.
Overall, TORREYA GUARDIANS IN THE MEDIA includes news reports in these science journals: Nature, Nature Climate Change, Science, Forestry Chronicle, Environmental Science and Policy. Non-academic news outlets and magazines have also reported on Torreya Guardians: New York Times, Los Angeles Times, Scientific American, Audubon, Orion, Sierra Magazine, Earth Island Journal.
Research papers published in FORESTRY JOURNALS have also paid a good bit of attention to the actions of Torreya Guardians. Foresters have a more use-oriented and practical relationship with tree species than do conservation biologists. Owing to ongoing and expected climate change (and the impacts of warmth and drought already evident even among common native trees), an urgency manifests among foresters to move past the assisted migration controversy. Hence, Torreya Guardians is helpful in that we serve as the radical edge of a continuum of possible climate adaptations actions, as pictured in the image below.
Nevertheless, because it is professionals in CONSERVATION BIOLOGY rather than FORESTRY who decide the actions authorized for Florida Torreya climate adaptation under the Endangered Species Act, several of the key multi-author or review papers published in conservation biology or botany journals will be focal points below. These demonstrate the high visibility that Florida Torreya receives.
4A. ACCESS PAPERS ON ASSISTED MIGRATION CONTROVERSYwas formed to explore and aim for a coauthored statement on whether and how to professionally move forward on this new tool in conservation biology for assisting species and ecological communities in moving in sync with the expected shifts in climate zones. Two multi-author papers resulted from that initiative: David M. Richardson and 22 coauthors in 2009; then Mark W. Schwartz and 30 coauthors in 2012. The citizen actions of Torreya Guardians were mentioned in both papers, as below.
Conservationist scientists, activists, managers, journalists, and others who need to become familiar with the 21st century controversy over assisted migration (a.k.a. managed relocation, assisted colonization) as a new tool for climate adaptation not only of endangered species but of other plants and animals unlikely to track the rapid movement of climate zones on their own may access the SCHOLARLY LINKS webpage on this website, as below.
Although the modern debate about assisted migration began around 2007, prominent conservation biologists recognized decades earlier that, should global warming continue, humans would indeed need to play a role in assisting species to migrate to cooler realms.
Below is the first widely-cited CONSERVATION BIOLOGY paper, 1985, to recognize that GLOBAL WARMING would make HUMAN ASSISTANCE IN MIGRATION necessary. Published in the journal Bioscience, this paper by Robert L. Peters and Joan D.S. Darling is also highly recommended for its thorough and well-written overview of the basic concepts in conservation biology. EXCERPTS: "... If estimates of a several-hundred-kilometer poleward shift in temperate biotic belts during the next [21st] century are correct, then a localized population now living where temperatures are near its maximum thermal tolerance would have to shift northward at a rate of several kilometers per year to avoid being left behind in areas too warm for survival...."
"... Although some species, such as plants propagated by spores or dust seeds, may be able to match these rates, many species could not disperse fast enough to compensate for the expected climatic change without human assistance." (p. 711)
"... If such measures are unsuccessful, and old reserves do not retain necessary thermal or moisture characteristics, individuals of disappearing species may have to be transferred to new reserves.... "It makes sense to locate reserves as near the northern limit of a species' range as possible, rather than farther south, where conditions are likely to become unsuitable." (p. 715)
• "The Greenhouse Effect and Nature Reserves", by Robert L. Peters and Joan D.S. Darling, 1985, Bioscience
Note: A 2016 Research Summary (Technical Report) of U.S. Forest Service (289 pages in pdf), references the above 1985 paper, as excerpted below: Effects of Drought on Forests and Rangelands in the United States: A Comprehensive Science Synthesis, James Vose et al., editors (collaborative effort of 77 scientists).Assisted migration, a management strategy where organisms are translocated from sites with suboptimal environmental conditions to sites with more optimal conditions, may become integral to conservation strategies as the rate of climate change increases (Peters and Darling 1985). Assisted migration can encompass a broad range of goals, from minimizing loss of biodiversity to preventing extinction, and operate at a range of spatial scales, from local to continental (Williams and Dumroese 2013). Seed transfer guidelines, because they determine transfer distances that avoid maladaptation (Johnson and others 2004) and can be re-projected using models of expected future environmental conditions (Thomson and others 2010), will play an integral role in the planning of assisted migration efforts under global change. (page 182)4B. FLORIDA TORREYA IS A FOCAL SPECIES IN ASSISTED MIGRATION CONTROVERSY
CONNIE BARLOW WRITES: I initiated the above Annotated Scholarly Links webpage in 2007, when journalist Douglas Fox published in Conservation Magazine a cover story: "When Worlds Collide". Our citizen-led assisted migration actions of Torreya Guardians was the introductory example in that article, but our effort was presented as just the preview of what would follow as climate change pressed on. Nearly simultaneously, the New York Times posted a story by science writer Carl Zimmer: "A Radical Step to Preserve Species: Assisted Migration". Through 2014, I could barely keep up on all the papers and news reports dealing with this utterly new and (to many) disturbing conservation strategy. Using "Google Alerts" to ongoingly learn of new publications has been a great help in recent years for keeping this page current, while preserving its complex history.
As of July 2016 the debate and the publications arising from it have tapered off enormously. "Assisted migration" (by whatever term used) is now a standard entry in revisions to management plans for continuing to conserve lands, waters, and biodiversity in this century of rapid climate change. Assisting native species in moving upslope, poleward, and toward climate refugia is now just one more acceptable tool for moving ahead with "climate adaptation." By far, public and private forestry professionals have moved the fastest and farthest in forecasting when and where native tree species should be given a boost, and implementation is well underway in the forests of Alaska and western Canada (hardest hit by climate change in North America.)
Florida Torreya as focal species: As of March 2019, if you do an internal "Find" for "Torreya" within this Annotated Scholarly Links webpage you will discover that this word appears 171 times at least 80 percent of which occur within the excerpts of papers, articles and news reports on assisted migration that are listed, linked, and annotated. 4C. FLORIDA TORREYA IS THE LONGEST-STANDING CASE STUDY ON ASSISTED MIGRATION IN CONSERVATION BIOLOGY
In 2008, at the annual meeting of the Ecological Society of America, a Managed Relocation Working Group
• 2009 - "Multidimensional Evaluation of Managed Relocation", by David M. Richardson, Jessica J. Hellmann, Jason S. McLachlan, Dov F. Sax, Mark W. Schwartz, Patrick Gonzalez, E. Jean Brennan, Alejandro Camacho, Terry L. Root, Osvaldo E. Sala, Stephen H. Schneider, Daniel M. Ashe, Jamie Rappaport Clark, Regan Early, Julie R. Etterson, E. Dwight Fielder, Jacquelyn L. Gill, Ben A. Minteer, Stephen Polasky, Hugh D. Safford, Andrew R. Thompson, and Mark Vellend, edited by Paul R. Ehrlich, 2009, Proceedings of the National Academy of Sciences.ABSTRACT: Managed relocation (MR) has rapidly emerged as a potential intervention strategy in the toolbox of biodiversity management under climate change. Previous authors have suggested that MR (also referred to as assisted colonization, assisted migration, or assisted translocation) could be a last-alternative option after interrogating a linear decision tree. We argue that numerous interacting and value-laden considerations demand a more inclusive strategy for evaluating MR. The pace of modern climate change demands decision making with imperfect information, and tools that elucidate this uncertainty and integrate scientific information and social values are urgently needed. We present a heuristic tool that incorporates both ecological and social criteria in a multidimensional decision-making framework. For visualization purposes, we collapse these criteria into 4 classes that can be depicted in graphical 2-D space. This framework offers a pragmatic approach for summarizing key dimensions of MR: capturing uncertainty in the evaluation criteria, creating transparency in the evaluation process, and recognizing the inherent tradeoffs that different stakeholders bring to evaluation of MR and its alternatives.This 2009 multi-author paper includes a "Supplementary information" pdf summarizing the application of their methods to 3 CASE STUDIES, of which Torreya taxifolia was case study #2. "Case 2: Translocating Torreya taxifolia to the Southern Appalachians"EXCERPT: ... More recently, 2 efforts have begun for the conservation of this species. Torreya taxifolia has been planted in North Carolina in an attempt to establish populations in that region (http://www.torreyaguardians.org/). This effort was done as an indirect response to climate change. The species is in declining in its native range with no sign of recovery. Proponents felt that this species 'belongs' in the region where they relocated it. They also feel that this intervention is the best chance for the species to survive, given its condition in its native range.
Evaluation of Case 2 by Stakeholder A, "Advocate for a Broad Distribution of Torreya taxifolia." Feasibility score is 4 (±1): Seeds are moderately easy to germinate; plant material in the form of cuttings are legally available through several botanical gardens in possession of numerous genotypes of known origin. Cuttings, however, take many years to reestablish apical dominance, so the process is slow. With a small number of mature female trees at Biltmore Gardens (Asheville, NC), the most available seed represents a very narrow subset of the genetic variability of the species. Although this is a federally listed species, it is possible to plant legally obtained plant material on private lands without seeking state or federal approval or permits. Acceptability score is 4.5(±0.5): The species is generally sparse and does not tend to form monospecific stands. The likelihood of this species becoming weedy is low. Focal Impact score is 4.5 (±0.5): There is no supportive evidence that we can conserve the species in its recent historical range. Torreya taxifolia represents 1 of 2 North American species in the genus and 1 of 5 North American Representatives in its family; 1 of 7 species in its genus and 16 species in its family worldwide (17). Loss of this species significantly erodes biodiversity. Collateral impact score is 4.5 (±0.5): This species is slow growing, produces few seed and is of relatively small stature as a mature tree. Being dioecious and producing relatively few seeds, this species would be relatively easy to control. Related taxa tend to be found either in localized patches or as subdominants in mixed forests. It appears unlikely to dominate and displace other Appalachian forest species [none of the 10 species in the family are known to be invasive when planted outside their range (18).
Continue reading the online pdf for the anti-assisted-migration perspective on Florida Torreya: Evaluation of Case 2 by Stakeholder B, "Advocate for Local Conservation of Torreya taxifolia." Feasibility score is 2 (±1)
Note: Case #1 in the above paper was on the Bay Checkerspot Butterfly. However, that case dropped out of continuing discussion when in April 2014, this mobile creature did something unexpected: "Endangered butterfly defies climate change with new diet and habitat". Case #3 centered on actions by commercial foresters. That leaves Florida Torreya as the focal species for discussion of assisted migration among conservation biologists.
• 2012 - "Managed Relocation: Integrating the Scientific, Regulatory, and Ethical Challenges" by Mark W. Schwartz and 30 coauthors, BioScience August 2012 (12 pp in pdf)List of all authors: Mark W. Schwartz, Jessica J. Hellmann, Jason M. McLachlan, Dov F. Sax, Justin O. Borevitz, Jean Brennan, Alejandro E. Camacho, Gerardo Ceballos, Jamie R. Clark, Holly Doremus, Regan Early, Julie R. Etterson, Dwight Fielder, Jacquelyn L. Gill, Patrick Gonzalez, Nancy Green, Lee Hannah, Dale W. Jamieson, Debra Javeline, Ben A. Minteer, Jay Odenbaugh, Stephen Polasky, David M. Richardson, Terry L. Root, Hugh D. Safford, Osvaldo Sala, Stephen H. Schneider, Andrew R. Thompson, John W. Williams, Mark Vellend, Pati Vitt, and Sandra Zellmer
ABSTRACT: Managed relocation is defined as the movement of species, populations, or genotypes to places outside the areas of their historical distributions to maintain biological diversity or ecosystem functioning with changing climate. It has been claimed that a major extinction event is under way and that climate change is increasing its severity. Projections indicating that climate change may drive substantial losses of biodiversity have compelled some scientists to suggest that traditional management strategies are insufficient. The managed relocation of species is a controversial management response to climate change. The published literature has emphasized biological concerns over difficult ethical, legal, and policy issues. Furthermore, ongoing managed relocation actions lack scientific and societal engagement. Our interdisciplinary team considered ethics, law, policy, ecology, and natural resources management in order to identify the key issues of managed relocation relevant for developing sound policies that support decisions for resource management. We recommend that government agencies develop and adopt best practices for managed relocation.
Note: The word "Torreya" appears 11 times in this paper. Key excerpts below.
EXCERPTS: ... Managed relocation is already being applied. Climate motivated translocations have been implemented with an endangered tree, Torreya taxifolia, in the southeastern United States (Barlow 2011; www.torreyaguardians.org) and with two butterfly species in the United Kingdom (Willis et al. 2009). Additional undocumented cases may be more frequent than is realized. For example, giant sequoia (Sequoiadendron giganteum) has been widely planted outside its historical range, although the motivation for such plantings remains unclear. Pressure to undertake managed relocation is likely to increase as the consequences of climate change become more apparent.
"...Therefore, it may be as important to discourage ad hoc managed relocation by enthusiastic individuals or groups as it is to provide guidelines for well-planned actions. So far, there has been little discussion of how best to limit unsanctioned private actions. This is a curious gap, given that one of the most visible cases of managed relocation is being conducted by a citizen action group (www.torreya guardians.org) that has moved a federally listed endangered plant species across state lines and 600 kilometers north of the historical distribution of the species, without any regulatory oversight (figure 1). This is not to imply a governance failure. Plants are afforded limited protection under the ESA, no oversight was required by the agencies, and this private group sought no public consultation. Although legislating or regulating restraint sounds simple, it is difficult to do so effectively. Private translocation, as the Lake Davis example mentioned above demonstrates, can be extremely difficult to detect and prevent. However, individuals and groups like the Torreya Guardians, who are motivated by conservation goals, may be dissuadable by education efforts. An ideal policy framework for managed relocation would not rely on a simple prohibition of private actions but, instead, would include outreach efforts designed to inform well-meaning conservation advocates of the harm that inappropriate translocation can cause.
Comments on Schwartz et al. 2012 by Connie Barlow were posted on this website, December 2012.EXCERPTS: ... A second reason why the 2012 paper's definition of "assisted migration" does not accurately depict the intentions of what we at Torreya Guardians are doing is that, with respect to our particular species, the core group of activists and private landowners believe that our actions are simply assisting this species in mirroring the natural northward migrations it is reasonably assumed to have undertaken in sync with the onset and intensification of previous interglacial episodes of climate warming during the Pleistocene. T. taxifolia's "historic native range" is, after all, also known to be a well-established "pocket glacial refugium," and thus it served as a vitally important refuge for eastern deciduous forest species at the peak of each glacial episode. That is why the late Paul S. Martin (Pleistocene ecologist) depicted Torreya taxifolia as having been "left behind in near time." See our 2004 paper on this topic, "Bring Torreya Taxifolia North Now".• 2017 - REVIEW: "Climate Change, Managed Relocation, and the Risk of Intra-Continental Plant Invasions: A Theoretical and Empirical Exploration Relative to the Flora of New England", by Jesse Bellemare, Bryan Connolly, and Dov F. Sax, June 2017, Featured Review, Rhodora.
What the word "migration" thus means in this context is not the annual migration of seasonally resident animal species but the epochal movements of the species at the timescale of Milankovitch cycles. By using the term "migration" to depict what we are are assisting Torreya in doing, rather than "colonization" or "relocation," we hope that regional residents near our project sites will be able to grasp that we are simply assisting this endangered species in doing what it naturally has done in previous warming periods. The term "assisted migration" thus has a far less interventionist aura to it than does the hegemonic feel of "colonization" or "relocation."
...In my view, until conservation biologists and managers and the public at large are given an opportunity to reflect on how long-lived species and genera of plants (such as Torreya) have indeed had to migrate long distances in the past, this issue of "managed relocation" will continue to foment more discord than necessary. We must cast what we are doing (or thinking about doing) not in the light of purely artificial intrusions in natural ecological dynamics but rather as necessary assistance in helping plants do what they have naturally done over the course of millennia and millions of years.
Indeed, I would not have initiated the Torreya Guardians movement simply on the basis of experiencing the species as doomed and feeling sorry for it; a deep-time paleoecological perspective (which I gained largely thanks to Paul S. Martin and Hazel Delcourt) was the crucial impetus moving me into action. My sense was that the managers and ecologists in charge of the Endangered Species Act (ESA) management of Torreya taxifolia lacked this perspective, and thus would continue to constrict their management focus exclusively to the ever-degrading "historic range" in Florida. Sadly, this proved to be true: In June 2010 Torreya Guardians were the only participants to vote "Yes," when the USF&WS staffer in charge of the ESA management plan update for T. taxifolia asked the gathered advisors whether a "pilot project" to test planting Torreya taxifolia to the north of its historic range should be added to the management plan. (You can access ours and other comments via: http://www.torreyaguardians.org/esa-recovery-plan.html.)
Frustrated by the lack of a deep-time perspective by the ESA advisory group for Torreya, I wrote and posted online the essay that I am grateful the 2012 Bioscience paper chose to include in its references cited: "Paleoecology and the assisted migration debate: Why a deep-time perspective is vital". This 12-point summary aggregates the data and develops strong scientific reasoning in favor of assisted migration for Torreya taxifolia. The essay also advocates a shift in the foundational paradigm from assuming 1491 is the proper time-standard for assessing native range to a "deep-time" perspective grounded in a paleoecological understanding that native ranges for all plants in temperate latitudes of the Northern Hemisphere have undergone substantial altitudinal and/or latitudinal migrations that have tracked changes in climate during the past several million years of Pleistocene glacial and interglacial cycles.
Note 1: Barlow's above comments were written in 2012. In 2015 (following a site visit to a 19th-century horticultural planting of Florida Torreya along the Chattahoochee River by Columbus GA), she revised her "glacial relict hypothesis" to offer the possibility that at whichever glacial episode during the Pleistocene Florida Torreya extended its range into Florida while losing its populations northward, it may never have been able to return northward again. That is, Torreya may have had to survive previous interglacial warm times in its current Holocene range. It is only the anthropogenic warming within the last hundred years that pushed this species over a physiological threshold of tolerance. Access the full explanation of this, and the Chattahoochee Torreya Tree VIDEO at this section on the Learnings webpage.
Note 2: The lead author of the above paper, Mark Schwartz, was the lead scientist exploring Florida torreya's decline in field studies in the early 90s; he is also the author of the anti-assisted-migration Torreya paper that was paired with the Barlow and Martin pro-assisted-migration Torreya paper in the Forum section of the Winter 2005/5 issue of Wild Earth.EXCERPT RE TORREYA: In the well-documented case of T. taxifolia, a private group called the Torreya Guardians has already launched unofficial managed relocation efforts aiming to naturalize the species at sites in the southern Appalachians, where the tree apparently grows more successfully than within its small native range on the coastal plain (Barlow and Martin 2004; but see Schwartz 2004).• 2017 - INVASIVE SPECIES ADVISORY COMMITTEE: "Managed Relocation: Reducing the Risk of Biological Invasion" - U.S. Department of the Interior, December 2017 (3 pages plus citations). ISAC Members: Edward E. Clark, Jr. (Wildlife Center of Virginia), Dan Simberloff (University of Tennessee), Mark Schwartz (University of California - Davis), Brent Stewart (Hubbs-SeaWorld Research Institute), and John Peter Thompson (Maryland Nursery and Landscape Association).EXCERPTS: ... In order to further Action 4.1.3, a Managed Relocation Task Team was established under the auspices of ISAC. This paper reflects the work of that task team, including internal group discussions, expert consultations, and literature review. The Task Team considered two parallel bodies of science to inform the analysis: a) the species translocation literature (Schwartz and Martin 2013; Seddon 2010), particularly as it relates to changing climates and b) a parallel, more empirically rich and much larger literature on the harmful consequences of invasive species on ecosystems (Mack et al. 2000) and on prediction and management of the risks of invasion (Hulme 2009; Kolar and Lodge 2002; Simberloff 2009; Thuiller et al. 2005). See Annex 1 for examples of managed relocation scenarios, Annex 2 for a list of referenced literature, and additional as citations for further reading.Alert by Connie Barlow: Two of the authors of this 2017 DOI policy statement have been among the strongest critics of assisted migration (managed relocation) of Florida Torreya since the onset of this controversy:
The task team offers the following key finding and recommendation to strengthen federal capacities to reduce the risk of biological invasion being facilitated through managed relocation practices....
At a minimum, the national policy and any supporting policies should:A. Limit the use of managed relocation to extraordinary circumstances;EXCERPT from Annex 1: Private Landowner Effects on Public Lands - Private land managers have the capacity to a affect public lands by introducing non-native species to their property with little or no ecological justification. These species may spread onto federal lands creating a potential need for land managers to either declare the species an invasive species or of conservation value. The Torreya Guardians began a program to actively spread Torreya taxifolia more than a decade ago (http://www. torreyaguardians.org). The group began with an effort to expand this species' range from northern Florida and southern Georgia over 600 km northward to North Carolina. The group has continued the spread of T. taxifolia as far north as Michigan and New Hampshire and west to Oregon with apparently no effort for ecological justification. In all cases the group has endorsed private plantings of this federally listed endangered tree species on private lands in a manner that is ecologically unjustified and risky, though they have not violated any rules or guidelines adopted by any governing body...
B. Delineate conditions that constitute legitimate exceptions to E.O. 13571 (e.g., imminent extinction of a keystone species), recognizing that the national need that may supersede the caution imposed by the executive order;...
Factual correction by Connie Barlow: Torreya Guardians did not move the species into Oregon; that was done by a private landowner in Oregon several decades before the group was established; the group did accept 3,900 seeds offered by the Oregon grower in 2016, for experimental plantings east of the Mississippi.• Daniel Simberloff, well known for his long leadership in invasive species policy, is coauthor of "Assisted colonization is not a viable conservation strategy", 2008, Trends in Ecology and Evolution, which is the most-cited anti-assisted-migration paper in the academic literature. It includes this direct mention of the torreya controversy:"... A recent position paper by the Ecological Society of Australia supports assisted colonization as a management response to climate change (http://www.ecolsoc.org.au/Position_papers/ClimateChange.htm). Other organizations could follow, driven by desperation in the face of anticipated species loss. Indeed, some scientists have claimed that rejecting assisted colonization will 'greatly increase the threat of climate-driven extinction' . At least one private group has already taken matters into its own hands: the 'Torreya Guardians' (http:// www.torreyaguardians.org) are planting seeds and seedlings across the eastern USA to expand the range of an endangered conifer, Torreya taxifolia, whose modern distribution is confined to the Florida panhandle. These events signal the emergence among some conservationists of a new philosophy regarding species introductions that is at odds with the traditional objective of preservation...."• Mark Schwartz did a great deal of field research on Torreya taxfiolia (with many publications) in the 1990s. (An internal find for "Schwartz" within this webpage turns up 28 instances.) The issue of assisted migration (managed relocation) as a potential conservation action to assist this endangered species first appeared in the Winter 2004/5 Forum of Wild Earth in which Schwartz wrote the anti-assisted-migration opinion piece in contrast to the pro-assisted-migration piece by Connie Barlow and Paul S. Martin. His leadership on this issue continued, culminating in first authorship of the 30-coauthor paper linked and annotated above.
Part 5. U.S. Forest Service Leads the Way in Assisted Migration Policy
5A. U.S. FOREST SERVICE LEADS THE WAY IN U.S. GOVERNMENT FOR ASSISTED MIGRATION POLICY.
• REPORT: "Assisted Migration"
EXCERPTS: Evidence suggests that species have responded individually during historic periods of dramatic climate change through geographic migrations to and from unique glacial refugia. Recent research has demonstrated that many tree species are already undergoing distribution shifts in response to climate change, with different studies highlighting species that are moving poleward and higher in elevation, or moving east-west to track changes in moisture availability. Despite the complexities of forecasting species range shifts into the future, the underlying challenge still remains that many species will face extinction or local extirpation if they do not acclimate, adapt via natural selection, or migrate to new suitable habitats as conditions change.
EXCERPTS cont: Given the observed and projected rates of change, there is a substantial risk that some species will be unable to migrate quickly enough to track change. Natural migration over long distances requires several generations, and this process is slow because trees require several years to get to reproduction age, and regeneration opportunities may be limited for a variety of reasons. Recent estimates indicate that post-glacial migration rates for many tree species were 100 to 500 meters per year. Recent rates of change for particular locations in the US have been even more dramatic, with rates of change from 1,000 to 10,000 meters per year for large areas of the Midwest, Great Plains, and Southeast, as well as isolated locations in the western US. These distances are a function of climate change rates ("climate velocity") and spatial climatic variation due to topography.
For species with very specific habitat needs or ranges limited by physical barriers, such as fragmentation or geographic features, this may mean that the entire species could be at risk of extinction or extirpation due to climate change.
... Studies involving reciprocal transplants of different species along large gradients have demonstrated the potential for assisted migration to benefit tree species and local populations. For example transplant studies of white spruce in Quebec showed that physiological traits such as photosynthetic rate and stomatal conductance were relatively plastic between populations and suggested that southern seed sources might be used in northern locations to increase growth and productivity without sacrificing seedling survival. Promising results have been demonstrated for species with more restricted ranges as well. Trials with whitebark pine demonstrated that seeds can be successfully germinated and grown large distances (800 km, 500 miles) to the north of the current species range boundary seed sources from Oregon and Washington performed well in locations in northwestern British Columbia . These studies, and others, have demonstrated that assisted migration is a reasonable option to help populations and species occupy areas of projected suitable habitat under climate change. Furthermore, assisted migration doesn't necessarily need to be implemented as a widespread action to be successful. Even if small founder populations of individuals can survive beyond existing ranges, they may contribute genetic diversity associated with warmer climates to native populations such that the native populations might have a better chance to adapt through natural selection....
Within the USDA Forest Service, Regional Geneticists have recommended a "no regrets" approach to considering assisted migration and seed transfer as a climate adaptation strategy in the 2012 report "Genetic Resource Management and Climate Change: Genetic Options for Adapting National Forests to Climate Change."...
This USDA report links to: "Adaptive Silviculture for Climate Change.
Part 6. CONCLUSION: Assisted Migration Now
6A. OVERVIEW & ADVOCACY BY CONNIE BARLOW, 2019called forth by immersion in paleoecological literature (especially Quaternary timeframe):
Any decision to implement genetic engineering on Florida Torreya and/or decide yet again to refrain from initiating "assisted migration" pilot projects as part of the recovery plan update process in 2019 will need to set that decision within the context of the actual scholarship and debate on this breakthrough issue in conservation science. Florida Torreya decision-making as part of the official species recovery plan will necessarily play on the world stage.
That the Department of Interior's "Invasive Species Advisory Committee" came out with such a strong statement against "managed relocation" in December 2017 (excerpt is immediately above), and that Torreya Guardians was singled out as a negative example, is important to consider from an agency perspective (Fish & Wildlife Service being part of DOI). That is why, in her comments re the 2019 recovery plan update (directly below), Barlow called attention to the new-in-2018 Historic Groves webpage. There, documentation achieved over the years during site visits by Torreya Guardians to northward plantings of now-mature specimens provide solid evidence that Florida Torreya (which has long been suspected of poor dispersal capabilities) has proved non-invasive in the mountains of North Carolina.
Currently, it appears that the individuals and institutions officially involved or expressing research interest in recovery of Torreya taxifolia have turned concern away from the long-standing questions of invasiveness and ability-to-thrive in northward locations (especially given the decade+ experience of healthy and seed-productive ex-situ groves in northern Georgia) and have recently expressed concerns about assisted migration primarily from the standpoint of possible pathogen transmittal. (See Part 1 and Part 2 of this webpage.) If that is indeed the case, then developing guidelines for guarding against pathogen transmittal would seem to be the primary action to accompany authorization of translocations of plant materials within and beyond Florida and Georgia as part of pilot project experimentations for discerning whether cooler habitats could diminish the lethal effects of any and all pathogens that have long been attacking Florida torreya in its glacial refugium. Here, too, documentation achieved by Torreya Guardians could be helpful: The plant materials least harmed by fungicides and most thoroughly subject to cleansing are ripe seeds. Please consult our new-in-2018 Free-Planting Seeds webpage for a photo-essay of documented experiments and learnings of our half-dozen years of testing various practices and habitats for placing seeds directly into regrowth forest sites, with the goals of maximizing success and minimizing herbivory, while setting in place long-term field experiments with minimal human labor and essentially no cost.
6B. PRIOR PUBLISHED ADVOCACY BY CONNIE BARLOW
• October 2018, Connie Barlow submitted Comments for the Recovery Plan Update:
• A final excerpt from my chapter in the 2009 book already excerpted and cited highlights the deep-time perspective
In her comments, Barlow pointed to several informative webpages on the Torreya Guardians website that should be taken into account in updating the plan, notably:
Since then, another webpage of actions has been added:
• Seed-Planting Experiments (a.k.a. "Freeplanting")
As well, this Brink of Extinction page was revised March 2019 in order to better lay out the argument (with sources linked) in favor of assisted migration of Florida Torreya.
Barlow's filing also stated, "Please add me to your e-list for receiving whatever communications you routinely send to your science advisors and area stakeholders. All citizens in the USA are stakeholders for endangered species. We Torreya Guardians have demonstrated our concern and care for this tree."6C. BARLOW ADVOCACY UPDATE, 2022
"Deep Time Lags: Lessons from Pleistocene Ecology",
by Connie Barlow, 2009, (9 pp. pdf)
Chapter 10 of Gaia in Turmoil: Climate Change, Biodepletion, and Earth Ethics in an Age of Crisis,
Eileen Crist and Brruce Rinker, eds., MIT Press
EXCERPT: ... In conclusion, the deep-time perspective that comes naturally to those who work in the realm of geophysiology can now become the lens through which conservation biologists and other biodiversity activists go about their work. Specifically, the deep-time perspective encourages conservationists to revise the parameters we use for judging which species are native to a region. It also encourages us to be mindful of time lags in biological adjustments to shifts in climate, and thus in how we read the past and how we prepare for the future.
PHOTO ABOVE: This herbivory-free "freeplanted" torreya emerged from seed that had inadvertently been planted by Barlow right next to an evergreen Polystichum fern in NE Alabama. A major learning accrued: Planting seeds (at least 3 inches deep for protection against seed predators) and alongside evergreen ferns provides excellent camouflage for escaping herbivory by deer.
• UPDATE: 19 MAY 2022 Connie Barlow submitted a 2-page "Request" for the (newly appointed) director of the U.S. Fish & Wildlife Service to review the citizen accomplishments of Torreya Guardians. Barlow concluded this way:"REQUEST: Please have a high-level, policy staff person visit the Torreya Guardians website: http://www.torreyaguardians.org/ From the home page, click on the link titled, "Case Study of Agency Failure." As well, our "Historic Groves" link is intended to be a strong and visually rich survey of how well the climate in the Appalachians and northward supports this glacial relict's health: notably its ability to fight a range of native diseases that have made the species functionally extinct in its historically native range. As well, do take a look at our documentation of what we have learned, especially to educate and guide volunteer planters via our "Propagation" page. Finally, please consult with USDA climate lead, Chris Swanston, who is well situated to educate conservation scientists in FWS about the forestry research scholarship that has welcomed "assisted migration" as a climate adaptation tool for timber management and forest ecosystem services. A well-regarded summary of the forestry science on this topic is a wikipedia page I coauthored in 2021 with a Canadian: "Assisted migration of forests in North America." I look forward to the possibility of Florida torreya becoming a highlighted achievement of FWS for the 50th anniversary of the ESA, instead of a sad example of ongoing climate denial and hostility toward citizen contributions."
• UPDATE: 8 AUGUST 2022 Connie Barlow submitted a comment on the proposed federal regulation to eliminate "historical range" as the sole locus for endangered species recovery. After voicing a YES to the proposal, she posted a 5-page PDF that offered RECOMMENDATIONS FOR IMPLEMENTATION:
1. Create implementation frameworks and policies that are distinct for plants.
2. Encourage nongovernmental entities to use the ESA "exception" for plants.
3. Follow the lead of the USDA Forest Service [in their own "assisted migration" terminology and actions.
4. Facilitate respectful dialogue and understandings of worldview differences.
• Barlow Comment, 5-page PDF here or here
• Barlow summary of key institutional comments among the 553 posted (10 pages PDF)
• UPDATE: 15 NOVEMBER 2022 Connie Barlow posted on youtube a richly illustrated HISTORY OF TORREYA GUARDIANS: VIDEO EPISODE 35: Torreya Guardians - Reflections by Connie Barlow
While cleaning and sorting torreya seeds freshly harvested from a private home in Clinton, NC, Connie extemporaneously delivers the history of significant beginnings, achievements, and frustrating institutional obstacles that she and other volunteers encountered during nearly two decades of action and advocacy in behalf of this endangered subcanopy tree.
The first 5 minutes is where she explains the importance of the paleoecological understanding of Florida Torreya as a glacial relict. Later, she offers why this deep-time understanding helps distinguish ULTIMATE from PROXIMATE causes of extinction.
VIDEO: 43 minutes, with timecoded table of topics in the youtube caption. Access the full list of TG videos.
* * * * *
End of "At the Brink of Extinction Why"
SUPPLEMENTARY MATERIALS BELOW
Classic Old Botany Papers Describe Torreya as Glacial Relict
EDITOR'S NOTE: This 1905 publication contains the first suggestion that Torreya's preferred habitat lies northward of its endemic Florida range. Access online the entire report.
Note that in this 1905 report, the author posits that"It is associated with a remarkable and somewhat extensive group of northern mesophytic plants, and the conclusion is irresistible that Torreya is a northern plant of the most pronounced mesophytic tendencies, and to be associated with such forms as the beech-maple-hemlock forms of our northern woods, our most mesophytic type of association."
PHOTO ABOVE: In 2013 AJ Bullard demonstrated on his Torreya taxifolia tree in Mt. Olive North Carolina that this species actually will produce both female cones (top branchlet) and male cones (middle branchlet) on a single individual. Lower left branchlet shows vegetative buds.
In an email to Lee Barnes on 9/29/16 Frank Callahan wrote of his mature Florida Torreya trees in Medford OR: "Both of these trees exhibit male and female 'flowers', which is unusual for this taxon."
"A Remarkable Colony of Northern Plants Along the Apalachicola River, Florida, and Its Significance"
by H. C. Cowles, 1905
Report of the Eighth International Geographic Congress
Held in the United States
"In this association one finds two of our most notable endemic plants Torreya and Croomia. It seems likely, then that we should regard Torreya taxifolia as a northern mesophytic left stranded to-day only in Florida.
"It presumably is one of the plants that failed to follow up the last retreat of the Pleistocene ice, and is preserved here perhaps because of exceptionally favorable topographic conditions."
Scientific Papers of Asa Gray, Vol II, 1841-1886", selected by Charles Sprague Sargent, 1889.
Editor's note: Genus Torreya is one of several plant taxa scrutinized by Asa Gray for the remarkably disjunct ranges including eastern Asia, eastern USA, and (to a lesser degree) California, along with fossil evidence in western Europe. Images below are drawn from his 1872 paper titled "Sequoia and Its History". These excerpts below will begin with p. 149 of the original document:... In the tertiary period, the geological botanists assure us, our own very Taxodium or Bald Cypress, and a Glyptostrobus, exceedingly like the present Chinese tree, and more than one Sequoia, coexisted in a fourth quarter of the globe, namely, in Europe! This brings up the question: Is it possible to bridge over these four wide intervals of space and the much vaster interval of time, so as to bring these extraordinarily separated relatives into connection? The evidence which may be brought to bear upon this question is various and widely scattered. I bespeak your patience while I endeavor to bring together, in an abstract, the most important points of it.
Some interesting facts may come out by comparing generally the botany of the three remote regions, each of which is the sole home of one of these genera, i.e., Sequoia in California, Taxodium in the Atlantic United States, and Glyptostrobus in China, which compose the whole of the peculiar tribe under consideration.
A few pages later Asa Gray offers a paleoecological explanation:"...My speculation was based upon the former glaciation of the northern temperate zone, and the inference of a warmer period preceding and perhaps following. I considered that our own present vegetation, or its proximate ancestry, must have occupied the arctic and subarctic regions in Pliocene times, and that it had been gradually pushed southward as the temperature lowered and the glaciation advanced, even beyond its present habitations; that plants of the same stock and kindred, probably ranging round the arctic zone as the present arctic species do, made their forced migration southward upon widely different longitudes, and receded more or less as the climate grew warmer ... so that different species of the same genus, as in Torreya, or different genera of the same group, as Redwood, Taxodium, and Glyptostrobus, or different associations of forest trees, might establish themselves each in the region best suited to their particular requirements, while they would fail to do so in any other. These views implied that the sources of our actual vegetation and the explanation of these peculiarities were to be sought in, and presupposed, an ancestry in pliocene or still earlier times, occupying the higher northern regions.Editor's note: For more detail on the fossil evidence of genera extant in eastern North America and eastern Asia, but now lost to Europe, access Asa Gray's 1878 paper "Forest Geography and Archaeology", republished in the same volume in pdf as above (Torreya is included in that paper.) I will close these excerpts first with a paragraph admirable for the breadth of knowledge and attention to deep-time mysteries that, alas, have gone missing among the credentialed in charge of the fate of Torreya today. Then, with a paragraph whose beauty and heart remind us of how diminished the human quest for knowledge became when "natural history" was left behind in favor of the more precise and quantitative inquiries of "science." A century and a half ago, Asa Gray wrote (p. 161):
"The genealogy of the Torreyas is still wholly obscure; yet it is not unlikely that the Yew-like trees, named Taxites, which flourished with the Sequoias in the tertiary arctic forests, are the remote ancestors of the three species of Torreya, no severally in Florida, in California, and in Japan...""... I must refrain from enumeration of the angiospermous or ordinary deciduous trees and shrubs, which are now known, by their fossil remains, to have flourished throughout the polar regions when Greenland better deserved its name and enjoyed the present climate of New England and New Jersey. Then Greenland and the rest of the north abounded with Oaks, representing the several groups of species which now inhabit both our eastern and western forest districts; several Poplars, one very like our Balsam Poplar, or Balm of Gilead-tree; more Beeches than there are now, Hornbeam, and a Hop-Hornbeam, some Birches, a Persimmon, and a Planer-tree, near representatives of those of the Old World, at least of Asia, as well as of Atlantic North America, but all wanting in California; one Juglans like the Walnut of the Old World, and another like our Black Walnut; two or three Grapevines, one near our southern Fox Grape or Muscadine, another near our northern Frost Grape; a Tilia, very like our Basswood of the Atlantic States only; a Liquidambar; a Magnolia, which recalls our Magnolia grandiflora; a Liriodendron, sole representative of our Tulip-tree; and a Sassafras, very like the living tree...."
"... I, for one, cannot doubt that the present existing species are the lineal successors of those that garnished the earth in the old time before them, and that they were as well adapted to their surroundings then, as those which flourish and bloom around us are to their conditions now. Order and adaptation did not wait for man's coming, nor were they ever stereotyped. Organic nature, by which I mean the system and totality of living things, and their adaptation to each other and to the world, with all its apparent and indeed real stability, should be likened, not to the ocean, which varies only by tidal oscillations from a fixed level to which it is always returning, but rather to a river, so vast that we can neither discern its shores nor reach its sources, whose onward flow is not less actual because too slow to be observed by the ephemera which hover over its surface, or are borne upon its bosom."
Excerpts from a detailed chapter on Florida Torreya (2015, by Kara Rogers, University of Arizona Press) are accessible at the google books site, page 101, for The Quiet Extinction: Stories of North America's Rare and Threatened Plants.
"By 2010, among wild populations of Florida torreya, only six plants were able to produce cones." Note: Several pages of detailed disease descriptions and experiments then follow.
"In 1955, officials at Torreya State Park, in the heart of Florida torreya habitat, reported a steep decline in the tree's populations. . . Seemingly overnight the situation had turned dire. Adult populations had been decimated, and there was no indication that the species was reproducing. Florida torreya, Kurz and Godfrey warned , was on the brink of extinction. . . . The disease seemed to be worse for trees that received full sunlight than for those in more shaded areas. But the result was still the same. . . The only individuals that were spared the disease were seedlings younger than six months. They presumably were started from seeds left behind by dead adults. By the 1990s, however, virtually all adult trees in the wild had been killed, and between 1,000 and 1,350 juveniles remained. Many young trees displayed symptoms of the disease, and over time their stems were killed off, one by one. The likelihood of their survival being prolonged depended in part on the size of their main stem. A larger main stem meant a more promising outlook, at least for a while. But once the main stem died or when a tree was down to three or fewer stems, each a foot and a half tall or less, death ensued.
"Possibly also affecting the survival of Florida torreya is damage to protective communities of mycorrhizal fungi that associate with Florida torreya. Nearly all of its mycorrhizal associates belong to the genus Glomus, which contains a number of species that help defend trees against root pathogens. The abundance of those fungi, however, appears to be greater among garden explants than among trees in native habitats. Wild Florida torreya currently inhabit heavily shaded areas, which, combined with the presence of disease, may limit the trees' ability to support beneficial mycorrhizal fungi.
Note: Several pages follow that detail current management projects attempting to restore Florida torreya in its historically native range. The remainder of the chapter highlights the work of Torreya Guardians, as imaged below:
2015 ADDENDUM by Connie Barlow:
Supplemental hypothesis on why Florida Torreya was "left behind" in its peak glacial refuge of Florida's Apalachicola River: Might Torreya taxifolia have become stranded in its peak glacial refuge, not so much because of the slow seed-dispersal capacities of squirrels (as hypothesized by Barlow here and here) but because of the absence of northward flowing rivers between Florida and the southern Appalachians? Barlow arrived at this hypothesis during a field visit to the largest remaining Torreya taxifolia in existence: the one along the Chattahoochee River, in the front yard of an historic-register home at the riverfront. (Click on video below.)
While visiting the sole remaining T. taxifolia in Columbus GA, Connie Barlow was struck by its location along a free-flowing section of the Chattahoochee River. The Chattahoochee is the main conduit between the peak-glacial plant refuge in n. Florida and the Appalachian Mountains. Might Torreya taxifolia have been "left-behind" in its Florida refuge because the Chattahoochee River flows southward? The tree could have dropped seeds into the river for a speedy journey south, but it would have been utterly dependent on the slower actions of squirrels for the the return trip north.
Visit the webpage that includes info, photos, and video of this oldest tree.
The International Union for the Conservation of Nature (IUCN) monitors endangered species via its IUCN Red List of Threatened Species. An update of its "critically endangered" Torreya taxifolia IUCN listing in 2011 includes these entries:The estimated 98% decline in mature individuals within the last three generations means that Torreya taxifolia meets the criteria for Critically Endangered under Criterion A2. The actual causes of the decline (the death of individuals and the reproductive failure associated with infection from a range of pathogens) is not well understood: recent surveys indicate it is continuing. The decline may be reversible in the future if those causes can be identified and controlled.
Restricted to a few ravines along the east side of the Appalachicola River in northern Florida and southern Georgia. Its total extent of occurrence is estimated to be about 200 km2 with an area of occupancy under 50 km2.
The current population is estimated to be between 500 and 600 trees. Of these, less than 10 are known to produce male or female cones (this species is dioecious). Individuals persist as stump sprouts. Before the start of the decline in the early 1950s, the population was estimated to have been more than 600,000. Since then there has been a decline of more than 98%.
Torreya taxifolia occurs along limestone bluffs on the Appalachicola River in a region with a warm and humid climate, occasionally influenced in winter by cold waves from the north that dip temperatures below the freezing point. It grows mostly in the shade of wooded ravines and steep, N-facing slopes under canopy of Fagus grandifolia, Liriodendron tulipifera, Acer barbatum, Liquidambar styraciflua, Quercus alba, and occasionally pines (Pinus taeda, P. glabra). Often these woods are hung with vines (e.g. Smilax spp., Bignonia capreolata). Another rare conifer, Taxus floridana, occasionally grows with Torreya taxifolia.
The most significant current threat to T. taxifolia is the continued reproductive failure associated with fungal pathogens. Individuals do not reach reproductive size before being top-killed. Recent research has identified a previously unknown species of Fusarium that may be the cause (J.A. Smith pers. comm. September 2010). Rubbing by deer is an additional problem as it causes physical damage and may also be a vector for disease transmission. Changes in landuse and fire regimes in surrounding areas along with changes in hydrology and soil chemistry linked to the construction of dams may also be implicated in its historical decline. Augmentation plantings within the natural range have proved to be susceptible to infection: no naturally resistant clones have been identified to date. Population viability analyses indicate that extinction within its native range is inevitable. Below: Sample graphic from the IUCN Red List page for Florida Torreya.
Image left from:
Taxonomy and Ecology of Woody Plants in North American Forests:
(Excluding Mexico and Subtropical Florida)
by James S. Fralish and Scott B. Franklin (Feb 8, 2002)
Hardcover: 624 pages
Publisher: Wiley; 1 edition (February 8, 2002)
Note the first sentence:
"Prior to glaciation and the accompanying colder climate, Torreya was circumpolar at high latitudes."
Notice the species richness centered over the Apalachicola region of northern Florida.
Illustration from "Contemporary richness of holarctic trees and the historical pattern of glacial retreat," by Daniel Montoya et al., 2007, Ecography 30:173-182.
Background note: To put the recent canker papers in context, peruse pages 5, 6, and 14 of the 2010 Recovery Plan Update. There you will find a brief history of research and findings on the multi-decadal quest to pinpoint the pathogen/cause of the sudden die-back of mature stems more than 50 years ago and the ongoing problems today.
Recent Papers on Stem Canker Pathology (chronological)
• "The Decline of Florida Torreya: An Endemic Conifer on the Edge of Extinction", by Jason A. Smith and Aaron Trulock, 2010, University of Florida School of Forest Resources and Conservation, research paper. UPDATE: As of 2021, this paper no longer exists online; it was not published in a journal and it was therefore not peer-reviewed, but these excerpts drawn from it may still be useful.EXCERPTS: Considered a common tree in its restricted habitat until just before WWII, by 1962 Florida torreya had declined so severely that the species was considered to be destined for extinction (Godfrey and Kurz, 1962). The decline of Florida torreya was first observed around 1938 (Alfieri et al., 1967). By the 1960s, no adult individuals could be found and the outlook for the species seemed very bleak (Alfieri et al., 1967). The rapid decline of the species was then attributed to an unknown fungal disease because of the abundance of leaf spots and stem cankers and the rapid nature of the decline (Godfrey and Kurz, 1962). Since then, Florida torreya has continued to decline and in addition to disease, has been subjected to changes in hydrology, forest structure, heavy browsing by deer and a loss of reproductive capability (Schwartz and Hermann, 1995). Despite these challenges, Florida torreya stems which have been killed by disease often re-sprout from the stump in a manner reminiscent of American chestnut following chestnut blight, although seed reproduction has been non-existent for decades in the wild (Schwartz and Hermann, 1999). Estimates show Florida torreya has declined 99% since pre-settlement population levels, from an estimated population of 357,500 individuals in 1914 to approximately 1,350 in the 1990s (Schwartz et al., 2000). It is believed that the population has declined further since 2000 to current estimates of 400–600 individuals (T. Spector, unpublished data, 2010).• "A Novel Fusarium Species Causes a Canker Disease of the Critically Endangered Conifer, Torreya taxifolia", by Jason A. Smith et al., Plant Disease, June 2011, 7 pp. with photos.
Despite several attempts to conclusively determine the causal agent responsible, disease etiology has not been previously elucidated (Alfieri et al., 1967; Alfieri et al., 1987; El-Gholl, 1985; Lee et al., 1995; and Schwartz et al., 1996). In the first pathology studies conducted on T. taxifolia (Alfieri et al., 1967), it was noted that disease symptoms of leaf spots, needle necrosis, defoliation and stem lesions were common on native and cultivated T. taxifolia. Several pathogens were isolated commonly from symptomatic needles (Macrophoma sp., Rhizoctonia solani, Sphaeropsis sp. and Sclerotium rolfsii), however, no pathogens were isolated from cankered stems and Koch's postulates (proof of pathogenicity) were not demonstrated. About 20 years later, El-Gholl (1985) implicated Fusarium lateritium as a causal agent by demonstrating this species' capacity to cause leaf spots, however, the causal agent of the canker disease remained unknown. Alfieri et al. (1987) completed more pathogenicity studies with a Phyllosticta sp., Xylocoremium flabelliforme and F. lateritium. They also completed Koch's postulates with F. lateritium as a leaf spot pathogen, but the canker-causing organism remained elusive. In 1991, Schwartz et al. implicated Pestalotiopsis microspora as the causal agent of the canker disease, having isolated the pathogen from 56 symptomatic plants and completed Koch's postulates on 10 stems. However, no information was given on the canker development, morphology or ability to cause mortality. Typically Pestalotiopsis spp. are considered opportunistic pathogens (Sinclair, 2005). Lee et al. (1995) investigated the endophytic and pathogenic chemical attributes of P. microspora infection and artificial inoculations resulted in stem canker development, however, again no stem mortality was observed.
Subsequent studies by Hermann and Schwartz (1997) implicated a Scytalidium sp. due to frequent isolation from cultivated and naturally occurring Florida torreya. Inoculation attempts led to small lesions on needles, but cankers were not observed.
In addition to biotic causes of decline, researchers have looked into changes in soils, drought, global warming, sunlight exposure and fire regime as possible causes of decline (Schwartz et al., 1995). Some of these environmental changes are thought to have occurred because of the building of the Woodruff Dam along the Apalachicola River in 1957 (Schwartz et al., 1995), and changing land uses in the surrounding areas. However, none of these environmental hypotheses have been demonstrated as a cause of the decline. The rapid nature of the decline during the period of 1938 to 1945 and numerous observations of disease symptoms provides ample evidence that a pathogen, possibly non-native, was involved (Schwartz et al., 1995).ABSTRACT EXCERPT: A canker disease of Florida torreya (Torreya taxifolia) has been implicated in the decline of this critically endangered species in its native range of northern Florida and southeastern Georgia. In surveys of eight Florida torreya sites, cankers were present on all dead trees and 71 to 100% of living trees, suggesting that a fungal pathogen might be the causal agent. To identify the causal agent, nuclear ribosomal internal transcribed spacer region (ITS rDNA) sequences were determined for 115 fungi isolated from cankers on 46 symptomatic trees sampled at three sites in northern Florida. BLASTn searches of the GenBank nucleotide database, using the ITS rDNA sequences as the query, indicated that a novel Fusarium species might be the etiological agent...
[Final paragraph]: Florida torreya faces numerous challenges to its future survival in its natural habitat. In addition to the canker disease, deer routinely cause damage to stems from antler rubbing. It is unclear whether they are attracted by the tree's aroma or seek out Florida torreya for some other unknown reason. Whether the wounds caused by deer serve as infection courts for pathogens, including the new Fusarium sp. (Fsp-1), is unclear and warrants further study. Additionally, since lesions on the larger plants in IE3 resulted in less stem girdling and no mortality, the host response to infection, particularly under different stress conditions, needs to be investigated. In addition to more research on the biology and management of CDFT, more work is needed to assess the various factors involved in decline of Florida torreya and how the species can be protected from extinction.
• "Host Range and Biology of Fusarium torreyae, Causal Agent of Canker Disease of Florida Torreya, by Aaron J. Trulock, 2012, 55 pp., (master of science thesis, University of Florida).ABSTRACT: Florida torreya is an endangered, endemic conifer with a limited range near the Apalachicola River. The species began to decline in the 1950's and the population has plummeted from an estimated 375,000 to approximately 1,000. Since 1967 many investigations have tried to determine the cause, including pathological and environmental factors. The Torreya Guardians propose recovering the species through assisted migration, where the species would be "re-introduced" into the southern Appalachian Mountains, the potential "historic" range of Florida torreya. In 2010 a previously unknown pathogen was discovered on Florida torreya, which causes stem cankers and stem girdling. The potential host range was investigated via artificial inoculations. Species tested included conifers whose range overlaps with Florida torreya, other species from the Torreya genus, and conifers from the southern Appalachian Mountains. One species with an overlapping range, Florida yew (Taxus floridana); two other Torreya species, California torreya (Torreya californica) and Chinese nutmeg yew (Torreya grandis), and five species from the Appalachian Mountains, Fraser fir (Abies fraseri), Red spruce (Picea rubens), White pine (Pinus strobus), Table mountain pine (Pinus pungens), and Eastern hemlock (Tsuga canadensis) were found to be potentially susceptible. The effect of temperature on the growth, sporulation, and spore dissemination was tested, also. Growth was maximized at 25 C, sporulation was maximized at 20 C, however, there was no significant difference in spore dissemination among the temperatures tested. The necessity of wounds for infection was investigated; it was found that F. torreyae cannot infect leaf or stem tissue without the presence of wounds.
FINAL PARAGRAPH: Fusarium torreyae appears to have the ability to complete its lifecycle if moved to a new, cooler location and would not be limited by the new environment. The movement of infected T. taxifolia plants into the southern Appalachian Mountains may spread this pathogen to a new area, to stressed, injured susceptible hosts and create a new epidemic. What is the value in moving one species to potentially imperil others?
Note by Torreya Guardians founder Connie Barlow - Although this paper is not peer-reviewed, p. 18 and the final two paragraphs (pp. 46-47) have been used as a reputable source for implicating northward plantings of Florida torreya by Torreya Guardians as dangerous for possibly spreading Fusarium torreyae to two Appalachian native trees: Fraser Fir and Eastern Hemlock. Because this warning is severe, it would be useful for the experiments leading to this conclusion to be published in full in a peer-reviewed journal. The experiment apparently discovered that the Fusarium "grows well and sporulates in the average summer and fall temperatures" of the southern Appalachians, but there is no mention as to whether population dieback occurs in the kinds of severe winter conditions that periodically occur in mountain locations, and there is no mention of actual testing of the Fusarium on the two tree species concluded as vulnerable.
Importantly, this paper was the first published mention that any danger might be associated with translocating Torreya plant materials geographically. A "novel Fusarium" (later named Fusarium torreyae) was first published as the definitive lethal disease the prior year (see the above, 2011, publication). Prior to Torreya Guardians' first reception of seeds from the Biltmore Gardens ca 2005, movement had been routinely conducted by agents associated with the official USF&WS recovery plan, beginning in 1989. No volunteer planter associated with Torreya Guardians has ever taken any material from the native site (Torreya State Park and surrounds) where the canker is rampant; in contrast, Atlanta Botanical Garden agents for many years have shuttled plant materials, tools, and boots directly between the diseased range and facilities in central Georgia. It is unfair to isolate Torreya Guardians as having potentially moved the then-unknown Fusarium, without acknowledging as well the many years in which researchers, experimenters, and even attendees at the 2018 Torreya Symposium in Torreya State Park might have unknowingly served as more direct vectors for northward movement of the Fusarium.
NOVEMBER 2019 UPDATE: Note by Connie Barlow - At first I ignored the Trulock master's thesis for the reasons noted above. But in November 2019 an audio interview with a primary institutional implementer of the Florida Torreya official recovery plan, JENNIFER CESKA (State Botanical Garden of Georgia), indicated that the fear of native conifer contamination in northward plantings (including official ex situ plantings in north Georgia) had ramped up to a level that "if we do see a problem, we would remove and burn that material." This insanity needs to stop. Century old groves of Florida Torreya in the vicinity of Asheville and Highlands NC confirm that the original trees and their nearby offspring show no disease expression, nor do other conifers in their surrounds. Ditto Florida Yew, which has coexisted with Florida Torreya along the Apalachicola presumably for tens of thousands of years (Florida Yew, as well, is a left-behind glacial relict). Despite the fact that the original 1986 recovery plan prescribed as Action 5, "inventory plantings at botanical gardens and arboreta and supplement existing plantings", it is only Torreya Guardians that not only has documented these historic groves and pointed to learnings thereby achieved. Links to the audio podcast and a transcript of key excerpts can be found in a November 2019 entry on the Torreya Guardians Reports webpage. For a lengthy argument on the importance of historic groves, see page 5 of the 26-page "Petition to Downlist Florida Torreya to Threatend" by Connie Barlow, September 2019.
• "Fusarium torreyae sp. nov., a pathogen causing canker disease of Florida torreya (Torreya taxifolia), a critically endangered conifer restricted to northern Florida and southwestern Georgia", by Takayuki Aoki, Jason A. Smith, Lacey L. Mount, David M Geiser, Kerry O'Donnell, 2013, Mycologia.EXCERPTS (in which the Fusarium is named and distinguished from closest Fusarium relatives): During a survey for pathogens of Florida torreya (Torreya taxifolia) in 2009, a novel Fusarium species was isolated from cankers affecting this critically endangered conifer whose current range is restricted to northern Florida and southwestern Georgia. Published multilocus molecular phylogenetic analyses indicated that this pathogen represented a genealogically exclusive, phylogenetically distinct species representing one of the earliest divergences within the Gibberella clade of Fusarium. Furthermore, completion of Koch's postulates established that this novel species was the causal agent of Florida torreya canker disease. Here we formally describe this pathogen as a new species, Fusarium torreyae.• "Two novel Fusarium species that cause canker disease of prickly ash (Zanthoxylum bungeanum) in northern China form a novel clade with Fusarium torreyae", by Zhou Xue, Kerry O'Donnell, Akayuki Aoki, Jason A. Smith, Matthe T. Kasson, Zhi-Min Cao, 2016, Mycologia.
... The available data suggests these three fusaria can be distinguished by host range in that F. torreyae is known only from Florida torreya (Smith et al. 2011), F. lunulosporum has been isolated only from grapefruit (Gerlach and Nirenberg 1982) and wheat (Gert van Coller, A-L Boutigny, A Viljoen pers comm) in South Africa, and F. tucumaniae has been recovered only from soybean in Argentina and Brazil (Aoki et al. 2003, O’Donnell et al. 2010). The identification of F. torreyae as F. lateritium by El-Gholl (El-Gholl 1985) and subsequent confirmation by Paul E. Nelson (D. Geiser pers comm) illustrate the daunting challenge presented by overly broad morphological concepts of fusaria, especially when applied to species that produce only sporodochial conidia. We speculate that the reported needle blight of Florida torreya induced by F. lateritium in a pathogenicity experiment (Alfieri et al. 1987) also can be attributed to F. torreyae; however, no isolate from this study was accessioned so the identity of this pathogen cannot be verified. Other examples of misplaced Fusarium spp. pathogenic to trees are provided by the etiological agent of coffee wilt disease in Africa, F. xylarioides Steyaert, and vascular wilt of pigeon pea (Cajanus cajan (L.) Millsp.) in Africa and Asia caused by F. udum Butler. The latter two species were classified in section Lateritium by Booth (1971), but molecular phylogenetic analyses have clearly established that they are nested within the African clade of the Gibberella fujikuroi species complex (O’Donnell et al. 1998, Geiser et al. 2005, Lepoint et al. 2005)
Note by Torreya Guardians founder Connie Barlow: This publication mentions a half-dozen Fusarium or other canker-causing pathogens that are all, with the exception of the Florida Torreya tree, hosted on plants that are of food value: a spice in China, cultivated grapefruit, wheat, a soybean cultivar in Argentina and Brazil, coffee bushes in Africa, and the pigeon pea that is cultivated in Africa and Asia. This indicates that the majority of documented pathogenic species of genus Fusarium attack plants of commercial value. Might one wonder: How many Fusarium species exist in southeastern North America and sometimes cause cankers on trees and other native plants, but are undiscovered because no researcher has been funded to isolate them? As well, might Fusarium torreyae be found elsewhere in the southeastern USA, but has not been documented because of low virulence in regions where native plants are less stressed by a deteriorating climate? Note: In the "comments" column of the USF&WS matrix of Record of Actions - Florida Torreya, a mention of Fusarium canker in the California Torreya appears: "The recovery plan suggests grafting [asexual propagation where the tissues (vascular cambium) of one plant are fused with those of another] with T. californica. However, T. californica is exhibiting some issues with cankers caused by pathogens with a different Fusarium species which is killing the cambium.EXCERPTS: Canker disease of prickly ash (Zanthoxylum bungeanum) has caused a decline in the production of this economically important spice in northern China in the past 25 y. To identify the etiological agent, 38 fungal isolates were recovered from symptomatic tissues from trees in five provinces in China. These isolates were identified by conducting BLASTN queries of NCBI GenBank and phylogenetic analyses of DNA sequence data ... Results of these analyses suggested that 30/38 isolates belonged to two novel fusaria most closely related to the Florida torreya (Torreya taxifolia Arn.) pathogen, Fusarium torreyae in Florida and Georgia. These three canker-inducing tree pathogens form a novel clade within Fusarium here designated the F. torreyae species complex (FTOSC).• "First Report of Fusarium Crown and Root Rot on Torreya grandis Caused by Fusarium oxysporum Species Complex in China", by Zhang Chuangqing, Shuya Zhang, X.L. Chen, Q.Q. Qi, H.Z. Lou, 2016, Plant Disease.
...Molecular clock estimates place the divergence of the FTOSC in the mid-Eocene , 40 Mya (O’Donnell et al. 2013), but it remains an open question whether this clade first evolved in the Old or New World. Furthermore, it remains to be determined whether F. torreyae is native to North America and restricted to T. taxifolia. Surveys for F. torreyae on Torreya endemic to China are warranted because it is the modern area of diversity of this genus (Li et al. 2001) and because the putative Asian origin of the CDZB pathogens could indicate that the most recent common ancestor of the FTOSC evolved in Asia.
EDITOR'S NOTE: A survey to determine whether a Fusarium is present and causes lethal cankers on Florida Torreya's closest cousin, California Torreya (Torreya californica), is surely "warranted" as well.
EXCERPT CONTINUES: ... Several species of Fusarium are capable of causing cankers on woody plants, and mixed infections frequently occur. For example, a particular FSSC species occasionally was found co-occurring with F. torreyae in cankers on Florida torreya (Torreya taxifolia) (Smith et al. 2011). Although both species could induce cankers, F. torreyae is considered to be the primary pathogen due to increased virulence and consistent isolation from a large number of cankers. By contrast the available data indicates the FSSC taxon should be regarded as an opportunistic (J. Smith pers comm).
ABOVE: FIG. 2. One of two most-parsimonious phylograms inferred from a combined RPB1-RPB2 dataset that strongly supported the monophyly of seven species complexes within Fusarium, including a novel clade of canker pathogens here designated the F. torreyae species complex.... [RED STARS ADDED BY EDITOR to show the "torreyae" complex that is newly split off from the long-established "lateritium" complex (which was the species identification of the canker-causing Fusarium prior to designation of F. torreyae as a separate species.]
EXCERPT of ABSTRACT: Torreya grandis cv. Merrillii is an important economic forest crop with a price as high as $75/kg in nut markets throughout humid regions of South China. In 2009, sporadic occurrence of crown rot disease was recorded in Shaoxing City, which produces 80% yields of T. grandis in China. In 2014, nearly 37% of orchards and 4.5% of trees were affected in Shaoxing. Symptoms were crown rot characterized by light-brown discoloration of the cambium, with brownish black necrotic areas which appeared on the roots and often advanced to the collar on most plants. Diseased trees showed reduced vigor and chlorosis on the foliage and eventually died.... To our knowledge, this is the first report of T. grandis crown and root rot caused by fungus belonging to the F. oxysporum species complex worldwide. Further work is needed to determine the clade of F. oxysporum to which the isolates pathogenic to T. grandis belong.• "Heterothallic sexual reproduction in three canker-inducing tree pathogens within the Fusarium torreyae species complex", by Xue Zhou, Kerry O'Donnell, Hye-Seon Kim, Robert H. Proctor, Gail Oehring, Zhi-Min Cao, 2018, Mycologia.EXCERPT of ABSTRACT: Fusarium zanthoxyli and F. continuum are sister taxa that are the etiological agents of canker disease of prickly ash (Zanthoxylum bungeanum) in northern China. These two pathogens, together with F. torreyae, the causal agent of canker disease of the critically endangered conifer Florida torreya (Torreya taxifolia) from northern Florida and southwestern Georgia, constitute a novel clade, the F. torreyae species complex.... Genotyping of 34 - 40 progeny from the F. zanthoxyli and F. continuum crosses confirmed that they were the products of sexual reproduction. However, only 36% of the progeny in the F. torreyae cross were recombinant, which was roughly half of the nonparental progeny expected with three markers segregating.• "Detection method for Fusarium torreyae the canker pathogen of the critically endangered Florida torreya, Torreya taxifolia", by Tyler J. Dreaden, Tania Quesada, Jason A. Smith, 2020, Forest Pathology.EXCERPT OF ABSTRACT: Recently, a canker disease caused by Fusarium torreyae was identified as the primary cause of Florida torreya decline. Efforts to restore and preserve the species in situ and ex situ are hampered by lack of pathogen-free planting stock, and there exists an interest in methods to verify pathogen presence in seeds and seedlings prior to collection and transport for planting. This paper presents a new species-specific diagnostic method that enables detection of F. torreyae and may allow for conservation programmes to ensure germplasm is free of the pathogen prior to planting.
EDITOR'S NOTE: This 2020 paper refrains from speculating that F. torreyae may have a non-native origin, and does not conclusively state that this pathogen was the cause of 1950s torreya blight in Florida.
EXCERPTS: The pathogen that might have caused the rapid decline in the 1950s is not known, but the Florida torreya is currently being affected by a canker disease caused by F. torreyae and it is hypothesized that this disease might be responsible for the species' rapid decline (Aoki et al., 2013; Smith et al., 2011). An ex situ conservation strategy was initiated with one cutting from each of 150 trees sampled and placed in four botanical gardens (Schwartz, 1993). Ex situ collections are ongoing (Smith et al., 2011), with the Atlanta Botanical Garden (Atlanta, GA) continuing to acquire new accessions and maintaining a large collection. Many of the botanical gardens were unable to maintain the collections, and most of the samples are currently found only at the Atlanta Botanical Garden. There is therefore a need to have ramets of these accessions at other locations to ensure their preservation. This is hampered by the necessity to ensure that the canker pathogen, F. torreyae, is not found in seed or seedlings that will be sent to the new locations where that pathogen is currently not found. This study was undertaken to develop a rapid and inexpensive PCR-based method to identify F. torreyae from culture to help screen samples for the pathogen before propagules of T. taxifolia are moved to new locations.
... Current T. taxifolia conservation/restoration efforts include ex situ collections. While this will help maintain the genotypes, the movement of the plants is a pathway for also spreading the canker pathogen to new locations. The assay developed here can be used to screen T. taxifolia plants or seed before they are moved to new locations and thus limit the spread of the damaging canker pathogen that could affect other hosts in new environments (Trulock, 2013).
Photos of Diseased Specimens • January 2004
by Connie Barlow • Torreya State Park
SPECIMEN #1. Steve Urse of Tallahassee with a reclining Torreya stem in an upland area near the ravines.
Below: Close-up of the lower stem, with healthy basal sprout on one side and a cluster of basals on the other, cropped by herbivory.
BELOW: Base of Specimen #1 in Florida on the LEFT, compared at RIGHT to an herbivore-damaged young stem in California, next to its healthy mature stem (photo 2005 by Connie Barlow).
SPECIMEN #2 (January 2004)
Multi-stem regrowth Torreya near bridge over creek. Nearby large-stemmed trees include Bald Cypress, American Holly, American Beech, Southern Magnolia. The five remaining photos show close-ups of diseased areas of stems and leaves.
OTHER PHOTOS OF TORREYA IN TORREYA STATE PARK
Access a webpage for a PHOTO-ESSAY BY GLENN RILKE of his periodic visits to surviving Torreya trees in historically native range in Torreya State Park (panhandle of Florida).
Note by Connie Barlow: Two early contributors to professional field studies of Torreya taxifolia, Mark Schwartz and Sharon Hermann, published in 1999 a paper on their study of Torreya californica in the field: "Is Slow Growth of the Endangered Torreya taxifolia (Arn.) Normal?", Journal of the Torrey Botanical Society. Their final paragraph:In aggregate, the results of this work suggest that the observed low growth rates of T. taxifolia might not be indicative of disease-induced stress. The similarity between T. taxifolia and T. californica growth rates and patterns is consistent with the hypothesis that T. taxifolia is growing normally within its environment. The infrequent expansion of terminal buds may simply be the way that these trees naturally grow in low light environments. Evidence of suppression and release growth pattern in tree rings, along with a preliminary observation that trees in high light environments grow more frequently than those in low light, support the hypothesis that growth in T. taxifolia is light limited. Given the continued lack of an identified primary disease agent, we recommend pursuing further tests of the light limitation hypothesis, and management to increase light levels above extant trees in the wild.Barlow adds: This is a helpful paper. My own natural history observations in 2005 (at a greater number and diversity of sites than the quantitatively driven experimental approach undertaken by Schwartz and Hermann) would add two interpretations: (1) Genus Torreya evolved as a definitive sub-canopy species (as are other members of the yew family); presumably with the assistance of mycorrhizae it is capable of living a very long time in a seemingly stunted state, until a canopy opening enables growth and also seed production on the individual branches that can access sufficient sunlight. (2) With the rare exception of the immense Torreya trees found along Swanton Creek north of Santa Cruz (which is artificial, given that the canopy redwoods were removed in the early 20th century, thus artificially releasing a population of subcanopy Torreyas to grow tall and to seed), Torreya seems to do best on extremely steep slopes, where the usual canopy giants (Coast Redwoods and Douglas-fir) are not found.
Access my PHOTO-ESSAYS OF CALIFORNIA TORREYA GROVES or my 2-part NARRATED VIDEO OF TORREYA CALIFORNICA.
"Coevolution of Cycads and Dinosaurs" paper by George E. Mustoe, The Cycad newsletter, March 2007.Barlow and Martin 2004 proposed that Torreya taxifolia might have gotten trapped in its peak-glacial pocket reserve (in northern Florida) for lack of its coevolved seed disperser, and thus was unable to geographically respond to the warming interglacial climate. The above paper suggests that another taxon of gymnosperm that thrived (along with genus Torreya) in the Jurassic period might have suffered from an inability to easily track climate change when the seed-dispersing dinosaurs died out.
Access in PDF two articles, for and against assisted
migration of Torreya taxifolia, published as the featured
Forum in the Winter 2005 issue of Wild Earth. Download
the pro and con articles separately for printing on standard
size paper. Or, for viewing the 2-article Forum as it
appeared in publication (wide-screen, with all illustrations),
download the "Forum."
FOR assisted migration, by Connie Barlow & Paul Martin
ANTI assisted migration by Mark Schwartz
FORUM (both articles for wide screen)
Standards for Assisted Migration (by Barlow & Martin 2004)
"Rewilding North America" The 18 August 2005 issue
of the prestigious science journal, Nature contains an advocacy
article that proposes "rewilding" close-kin of some of the
large mammals that went extinct in North America at the
end of the Pleistocene, 13 thousand years ago. By comparison,
the proposal to "Rewilding Torreya taxifolia" looks mild! To access
this amazing article, you can view or download it at
The Apalachicola as a Peak-Glacial Habitat
Palynologist Hazel Delcourt, botanist Rob Nicholson, and others have each independently concluded that the Apalachicola habitat in which T. tax is found is one of a small group of "pocket refuges" along the Gulf (and southern Atlantic) coasts in which the vast majority of warm and cool temperate plant species found crucial refuge when the Pleistocene continental glaciers achieved their peak advances during the past 2 million years. Without these refuges, it is likely that North America would have lost not only Torreya taxifolia but also its tuliptrees, sweet gum trees, bald cypress, hemlocks, and a host of shrubs and forbs (such as mayapple). How do we know this? Because Europe lost these species, presumably owing to unfortunate geography: southward migration blocked by the Mediterranean, Black Sea, Carpathian Mountains, etc.
ABOVE left: Tuliptree. ABOVE right: Sweetgum
BELOW left: Bald cypress (Taxodium) BELOW right: Franklinia
Indeed, the species name of Franklinia, Franklinia alatamaha derives from the only place this lovely tree was found the Altamaha River of southeastern Georgia before it vanished from the wild. The Altamaha River thus joins the Apalachicola (and the Tunica Hills of Louisiana) as a peak-glacial pocket refuge for plants of eastern North America.
ABOVE: Two of the three crucial peak-glacial pocket refuges include the Apalachicola River of the Florida panhandle and the lower reaches of the Altamaha River of southeastern Georgia (both shown in yellow; orange denotes the section of the Apalachicola containing T. tax).
"A Remarkable Colony of Northern Plants Along the Apalachicola River, Florida, and Its Significance"KEY SECTION:
by H. C. Cowles, 1905
Report of the Eighth International Geographic Congress
Held in the United States
"In this association one finds two of our most notable endemic plants Torreya and Croomia. It seems likely, then that we should regard Torreya taxifolia as a northern mesophytic left stranded to-day only in Florida.
"It presumably is one of the plants that failed to follow up the last retreat of the Pleistocene ice, and is preserved here perhaps because of exceptionally favorable topographic conditions."
Where Should "Native" Range Be During an Interglacial?
If the Apalachicola is, in fact, peak-glacial habitat for Torreya taxifolia, then we might conjecture that, for some reason, Torreya taxifolia (as well as the equally endemic, though not equally stressed, Florida yew) was unable to migrate north in tandem with a warming climate during the past 15,000 years. Thus where might its "native" range be at this point in an interglacial?
Learn about efforts to SAVE Torreya taxifolia from extinction and how our actions are legal.