genetic diversity

Dr. Johnny Randall, North Carolina Botanical Garden

The infamous Venus flytrap, Dionaea muscipula, found across North Carolina and into South Carolina, has been seen to be declining in recent years. It is currently under review for federal listing, is ranked G2 on NatureServe, and considered vulnerable by RedList. Threats to this charismatic plant include poaching, trampling, and changes in fire and hydrology. Dr. Randall of the North Carolina Botanical Garden is conducting a double-pronged conservation effort, collecting and banking seeds by maternal line, and doing genetic analysis across the populations. Results from the genetic data suggest four distinct clusters that closely match phylogeographic areas.

Contributing Author(s): 
Date Recorded: 
Wednesday, March 4, 2020

Dr. Sean Hoban, The Morton Arboretum, Taylor Callicrate, Species Conservation Toolkit Initiative, Chicago Zoological Society, Susan Deans, Plant Biology and Conservation Program, Northwestern University, Michael Dosmann, The Arnold Arboretum of Harvard University, Jeremie Fant, Chicago Botanic Garden, Oliver Gailing, University of Göttingen, Kayri Havens, Chicago Botanic Garden, Andrew Hipp, The Morton Arboretum, Priyanka Kadav, Michigan Technological University, Andrea Kramer, Chicago Botanic Garden, Matthew Lobdell, The Morton Arboretum, Tracy Magellan, Abby Meyer, Botanic Gardens Conservation International, Emma Spence, Center for Tree Science, The Morton Arboretum, Patrick Thompson, Auburn University Raakel Toppila, Seana Walsh, National Tropical Botanical Garden, Murphy Westwood, The Morton Arboretum, Jordan Wood, Illinois Natural History Survey, M. Patrick Griffith, Montgomery Botanical Center

Ex situ collections such as botanic gardens inspire and educate the public, provide material for scientific study, and produce material for ecological restoration. The challenge for an efficient and effective collection is safeguarding high genetic and ecological diversity in as few samples as possible, due to the relatively small resources available for conservation. A botanic garden might have resources to maintain a few to a few hundred plants of priority species in conservation collections, but not the thousands that seed banks can preserve. Providing scientifically grounded recommendations for the number of individuals that need to be conserved, and how to collect from the wild and manage collections over time, is a pressing need. Previous work using case studies and modeling of important biological traits has established the fact that some species must be sampled differently, and that widely used standard sample sizes might not be optimal practice for capturing the maximum diversity. We present here a comparative study of ex situ gene conservation in three southeastern oaks (Quercus georgiana, oglethorpensis and boyntonii) and two magnolias (M. pyramidata and asheii). Specifically, we use genetic datasets and resampling algorithms to: quantify how much genetic diversity has been captured in a global network of botanic garden collections currently, resample the wild population genetic datasets to determine how much genetic diversity could be captured by varying sample sizes, determine minimal sampling needed to capture 70% and 95% of the genetic diversity, and use a diminishing returns method to calculate optimal stopping points- when additional collection effort no longer provides sufficient gains. Between 62 and 72% of genetic diversity is currently safeguarded for the oaks, and about 80% is conserved for the magnolias. The recommended collection size depends on key decisions by curators about the type of genetic diversity that is valued, but may range from approximately 50 to 200 individuals. We hope that these findings motivate future seed collections from wild provenances for botanic garden collections and stimulate discussion on ex situ gene conservation goals and outcomes.

Date Recorded: 
Wednesday, March 4, 2020

Dr. Vivian Negrón-Ortiz, U.S. Fish & Wildlife Service, Ms. Melanie Kaeser, U.S. Fish and Wildlife Service

To protect and manage species listed under the U.S. Endangered Species Act requires the use of the best available science. Field-based studies on topics such as demography, reproductive biology, and seed ecology have provided sound conservation strategies for many imperiled plants. Unfortunately, understanding of relevant biology is still lacking for numerous rare species. Such biological information was lacking for Euphorbia telephioides, a threatened species primarily endemic to pineland flatwoods in the Florida Panhandle. This species is a perennial herbaceous plant that has suffered from the effects of habitat loss, degradation, and fragmentation throughout the entire range of its distribution in Florida. This is the primary threat identified in the Recovery Plan of 1994, and remains the main threat to date. As part of a longterm study to understand the conservation requirements for the recovery of E. telephioides, three distinct populations were studied across the range of this species. We established one permanent plot in each population, and investigated size and reproduction, response to fire, and in situ seed germination and seedling survival from 2010-2014. Euphorbia telephioides plants are long-lived and survived fire by resprouting. This species is composed of males, females, and monoecious individuals with labile sex expression, a system that has the effect of ensuring outcrossing and thus contributing to genetic variability, but also guarantees pollination in the absence of cross-pollination. To minimize exposure to seasonally stressful conditions, both adults and seedlings exhibited obligate winter dormancy and facultative nonsynchronized summer dormancy as well as prolonged vegetative dormancy. Seeds survive < 1 year, denoting that there is no persistent soil seed bank that can be relied on to maintain populations in the face of environmental stochasticity. However, once seedlings are established in the soil, they resprout back after fire, favoring a hypothesis that seedlings contribute to E. telephioides persistence. In conclusion, E. telephioides displays traits that are part of a life history that is adaptive in the fire-prone habitats where this species occurs. Implications for in-situ and ex-situ conservation programs will be discussed.

Date Recorded: 
Wednesday, March 4, 2020

Dr. Matt Estep, Appalachian State University Jennifer Rhode Ward, University of North Carolina at Asheville

Many plant species are being driven towards rarity due to exploitation for food, medicine, or the nursery trade. Land managers in the Smoky Mountain National Park are particularly concerned about two plant species: cutleaf coneflower / Sochan (Rudbeckia laciniata), and ramps (Allium tricoccum). Both of these species are traditionally foraged for food and ceremonial use by the Eastern Band of Cherokee Indians, and parklands will soon open to limited collection by EBCI members. To ensure the health and vitality of these species, a combination of demographic and genetic data are being collected. These will be used to assess baseline genetic diversity and prioritize populations for conservation. Developing novel molecular tools for monitor imperiled plant species is one avenue towards safeguarding their futures, as these tools can be used to identify problematic reductions in genetic diversity over time.

Date Recorded: 
Tuesday, March 3, 2020

Laramie Smith, University of Georgia Dr. James Affolter, State Botanical Garden of Georgia and Department of Horticulture at the University of Georgia

As the herbal supplement and alternative health industries grow, foraging for wild medicinals is becoming a more common and profitable phenomenon. In addition to the financial incentive to harvest non-timber forest products (NTFPs), there is a cultural push to “return to the land.” These motivations have raised the prevalence of abusive foraging habits, such as poaching or over-harvesting, increasing the threat to certain useful plant species. Our project draws upon the literature and experiences of two stakeholder populations—foragers, and professionals in the field of resource management and conservation—to garner insights about how to improve our response to foraging abuses of threatened but profitable plant species native to the Southeast. We interviewed members from both populations and compiled a summary of their responses; compared current conservation rankings and practices to determine how well they reflected economic factors affecting plant populations; and conducted three case studies on potentially threatened native medicinal plants, assessing both alternative acquisition methods and potential therapeutic substitutes. While the project is on-going, initial results reveal three themes: conservation practices and policies do not adequately address plants that are at risk due to targeted collection for economic benefit; stakeholder populations (resource managers and foragers) do not interface effectively or frequently, but there is potential to work together based on a shared value set; viable alternatives exist for many threatened native medicinal plants, but these are understudied and only folklorically known. This pilot study suggests that foragers might already have the ideal tools for combating harvesting abuses within their own communities. If the foraging community and environmental regulators work in partnership, it should be possible to develop an interactive environmentalism that establishes a productive balance between use and preservation, economy and conservation. This could lead to a more integrated conservation model than those currently in place.

Date Recorded: 
Tuesday, March 3, 2020

Joe Davitt, Institute for Conservation Research, San Diego Zoo Global

Maintaining a plant species’ genetic diversity can contribute to adaptive potential, prevent inbreeding effects, and potentially preserve traits such as drought tolerance and disease resistance, all of which are critical in a changing climate. Seed collections are often the best method of conserving the genetic diversity of rare plant populations ex-situ, however most seed collections are made with no available genetic data from the target species. Ideally, this genetic data would give us a clear picture of which populations are the most critical to conserve and how genetically structured a species’ populations are in relationship to one another, but this can be a time consuming and costly process. Seed collection protocols, such as those published by the Center for Plant Conservation, can inform our general best practices, but as seed collectors we must also infer best practice on a species by species basis. The life history and reproductive biology of the target species, as well as our sampling methods can greatly impact the effectiveness of seed collections to capture the entire target populations’ genetic diversity. Taking all available information about a species into consideration, we can infer the best seed collection methods to ensure genetic conservation.

Contributing Author(s): 
Date Recorded: 
Tuesday, September 10, 2019

Manuel Luján, Jian Liu, Nathalie Nagalingum, California Academy of Sciences, Kunming Institute of Botany, Chinese Academy of Sciences

Rare plant species exhibit narrow geographic distribution and are often considered to have smaller populations and lower levels of genetic diversity compared to their more common relatives. The genus Cycas includes about 117 species, 32 of which are native to Australia and 20 occur only in the subtropical and tropical regions of Queensland. Most of the Queensland species of Cycas are known from only a handful of localities and their population characteristics remain to be investigated. Our main objective was to assess genetic diversity and population size of the rare species of Cycas and compare it them the more widely distributed species. We used RADseq to generate genomic data to estimate percentage of polymorphic loci (P), heterozygosity (Ho and He) and nucleotide diversity (π), and footage from unmanned aerial vehicles to estimate populations size. Our preliminary results suggest that rare species (C. terryana) have levels of genetic diversity that are comparable to more common species (C. ophiolitica and C. media). Population size of rare species (e. g. C. tuckeri) tend to be smaller than more common species (C. cairnsiana). Given that Cycas are long-lived plants, rare and small populations constituted by old plants, may be maintaining ancestral allelic variants from previously more widespread and common populations. Further study considering the populations demographic structure are needed to better understand this pattern and inform conservation efforts.

Date Recorded: 
Wednesday, September 11, 2019

Alexander G. Linan, Porter P. Lowry II, Allison Miller, George E. Schatz, Jean-Claude Sevathian, Christine E. Edwards, Saint Louis University, Missouri Botanical Garden, Institut de Systématique, Évolution et Biodiversité (ISYEB), Centre National de la Recherche Scientifique/Muséum National d'Histoire Naturelle/École, Pratique des Hautes Études, Université Pierre et Marie Curie, Sorbonne Universités, Donald Danforth Plant Science Center

The ebony and persimmon genus (Diospyros) is a diverse group of largely tropical trees and shrubs, comprising >800 species, many of which are poorly known, and/or are of dire conservation concern. Some of the most endangered members of the genus are endemic to islands of the Western Indian Ocean. The Mascarene Islands, comprising the islands Reunion, Rodrigues, and Mauritius is located east of Madagascar, and harbor 14 endemic species of Diospyros. Most of the species diversity is endemic to Mauritius are of dire conservation concern with the majority of species listed as either Critically Endangered or Endangered by IUCN Red List assessments. Despite their conservation status, nothing is known about patterns of genetic diversity or whether these sympatrically distributed and closely related species represent distinct genetic units. In this study we conducted population level sampling on all extant species of endemic Mascarene Diospyros and genotyped samples using 2bRAD seq in order to: 1) clarify species limits within the group, 2) determine and compare levels of genetic diversity across species and, 3) assess patterns of genetic structure within species and prioritize populations for conservation efforts. We found the morphologically described species correspond to unique genetic units despite the presence of hybrids and provide recommendations for future/ongoing conservation efforts.

Date Recorded: 
Wednesday, September 11, 2019

Fred Gouker, Abigail Moore, Kevin Conrad, Margaret Pooler, USDA-ARS U.S. National Arboretum, Floral and Nursery Plants Research Unit, Enviromental and Plant Biology Department, Ohio University

Sassafras albidum is a well-known, ecologically important tree that is dispersed throughout the Eastern United States. Its root and bark oil were commonly used as a flavoring agent for many products including tea and root beer. This tree can be used to restore depleted soils and rehabilitate disturbed sites. Sassafras also serves as a host plant for the Spicebush Swallowtail butterfly, providing a strong wildlife value. S. albidum is a member of the Lauraceae family that is presently threatened by laurel wilt disease originating from the fungus Raffaelea lauricola. Laurel wilt and is transferred by the insect vector, redbay ambrosia beetle (Xyleborus glabratus) through burrowing. While fungicides may help treat individual trees, the drastic spread of this disease has led us to believe broad-scale, preventative, efforts must be made to conserve the genetic diversity of this species. In this study we strive to isolate microsatellite loci from a diverse collection of sassafras found across the eastern and midwest regions of the United States to help protect and potentially recover this tree species through germplasm conservation before laurel wilt advances through the extensive native range of Sassafras and becomes a broad-scale epidemic.

Contributing Author(s): 
Date Recorded: 
Wednesday, September 11, 2019

Kyle L. Gunther, Sula Vanderplank, Jon P. Rebman, Andres Orduño Cruz, & Lluvia Flores-Rentería, San Diego State University, San Diego Natural History Museum, San Diego Zoo Global, Centro de Investigaciones Biológicas del Noroeste

California and the Baja peninsula are home to high levels of floral abundance, diversity, and endemism. Much of this region is part of a biodiversity hotspot and therefore a conservation priority. The Mission Manzanita (Xylococcus bicolor) is endemic to this area, an ecologically and ethnobotanically important shrub, and the sole member of a monotypic genus within Ericaceae. Xylococcus bicolor is narrowly distributed from the middle of Baja California to the Los Angeles area, and has been predicted to experience up to 88% habitat loss due to climate change and development. However, little is known about its population structure, demographics, and genetic diversity, which may be useful information for conservation purposes. In order to fill this gap in knowledge, we are studying these aspects from a genetic perspective. Using a genome skimming technique to reveal thousands of single nucleotide polymorphisms, we are analyzing the population structure, genetic diversity, gene flow, and effective population sizes across the X. bicolor distribution. Preliminary results suggest the presence of intraspecific divergence and population structure, while niche models show loss of suitable habitat using climate change scenarios. We hope our study will provide useful information for land management and conservation decisions.

Date Recorded: 
Wednesday, September 11, 2019