Population genetic analysis of species of conservation concern provides information to devise management plans to effectively conserve the genetic variation of endangered species. One such endangered plant, Physaria globosa is a federally endangered species in the mustard family with a geographically restricted range that occurs in four disjunct locations in Indiana, Kentucky, and Tennessee along the watersheds of the Wabash, Kentucky, Cumberland Rivers. In this study, we sampled populations from throughout the range of P. globosa, genotyped them using 20 microsatellite loci, and assessed genetic diversity and structure within and among populations. The goals of the study were to understand: 1) levels of genetic diversity in P. globosa and whether populations show evidence of having experienced reductions in genetic diversity as the result of genetic bottlenecks, genetic drift, or inbreeding, 2) rangewide genetic diversity and structure in P. globosa and how genetic structure is affected by the disjunctions in the species range, and 3) implications for prioritization of in-situ and ex-situ conservation efforts. On average, P. globosa showed comparable levels of genetic diversity to other species of Physaria. However, some populations showed evidence of inbreeding, genetic bottlenecks, or decreases in genetic diversity, possibly due to anthropogenic or climate-related pressures and decreases in population size due to competition with invasive bush honeysuckle. Genetic variation was strongly structured into two main geographic groups, one in the northern part of the species' range (KY and IN), and the other in the southern part of the species range (TN), but some populations likely originated via long-distance dispersal. We also found significant isolation by distance, likely due to both life history characteristics and physical barriers associated with the complex topological structure of the landscape occupied by P. globosa, limiting population connectivity. Given the strong genetic structure found in P. globosa, several populations should be protected and managed within each geographic region to conserve genetic variation. Ex situ conservation will also be important to protect genetic diversity, particularly for populations that are difficult to access and manage. ### Competing Interest Statement The authors have declared no competing interest. United States Fish and Wildlife Service, Cooperative Agreement F19AC00621

Physaria is a species-rich genus native to the Americas that contains many locally endemic species of conservation concern. Physaria filiformis is a federally threatened annual species occupying glade ecosystems in Arkansas and Missouri. Previous genetic work in P. filiformis based on microsatellites identified a geographically isolated group of populations in the Ouachita Mountains that were strongly genetically divergent from the rest of the species despite apparent morphological similarity. This led to questions about whether the isolated populations were P. filiformis, populations of some other Physaria species, or an unrecognized new species. In this study, we conducted morphometrics and phylogenomic analyses based on 2b-RAD-seq data to understand: 1) which Physaria species is most morphologically similar to the Ouachita populations, 2) whether morphological characteristics distinguish the Ouachita populations from the most morphologically similar Physaria species, 3) the evolutionary relationships of the Ouachita populations with other geographically proximal Physaria and 4) whether phylogenomic data support the distinctiveness of the Ouachita populations. As previously hypothesized, we found that the Ouachita populations were most morphologically similar to P. filiformis. Morphological comparisons between the Ouachita populations and the rest of P. filiformis revealed that the Ouachita populations had smaller flowers, larger fruits, and distinct petal morphology. They also occupy a distinct substrate type and a different physiographic province. Phylogenomic analyses placed the Ouachita populations as sister to the morphologically divergent species P. globosa, with P. filiformis sister to P. globosa + the Ouachita populations. Including the Ouachita populations in P. filiformis would render the group non-monophyletic. This illustrates how the use of an approach combining both morphometrics and genetic data can resolve the taxonomy of a potentially distinct cryptic species, distinguishing it from close relatives. Based on this evidence, we determined that the Ouachita populations represent a distinct species, described here as Physaria ouachitensis . We discuss conservation implications for both P. ouachitensis and P. filiformis.

Conservation translocations are an established method for reducing the extinction risk of plant species through intentional movement within or outside the indigenous range. Unsuitable environmental conditions at translocation recipient sites and a lack of understanding of species-environment relationships are often identified as critical barriers to translocation success. However, previous syntheses have drawn these inferences from analyses of qualitative feedback rather than quantitative environmental data. In this study, we use a data set of 235 translocations conducted in the US to understand the influences of geographic and environmental factors on three metrics of translocation success: population persistence, next-generation recruitment and next-generation maturity. We use random forest models to quantify the relative importance of geographic and environmental factors that characterize dissimilarity between source and recipient locations, the position of recipient sites relative to species' ranges and niche metrics derived from these ranges. We also compare the importance of these variables with more conventional predictors (e.g. founder population size). Our results indicate that geographic and environmental variables can be as insightful as conventional variables for predicting plant translocation outcomes. The climate suitability of recipient sites, estimated using species distribution models, was the strongest relative predictor of whether a population persisted, with populations situated in more suitable climates displaying greater persistence. Next-generation recruitment and maturity were best predicted by niche metrics; species in more biotically limiting environments, including tropical regions and soils with high relative nutrient retention, as well as species with the broadest precipitation niches, were the least likely to attain these next-generation benchmarks. Synthesis and applications. Our study is one of the first to quantify the important role of spatial and climatic factors in rare plant translocation outcomes. We provide a novel geographic and environmental perspective on outcomes in plant translocations and demonstrate opportunities to improve translocation success not only by adhering to established best practice guidelines but also by integrating spatial modelling approaches into planning and management processes.

Determining the factors underlying rarity is essential for developing successful reintroduction programs with rare plant species. However, the influence of soil microbes on rare plant performance remains underexplored. In this study, we examined how changes in soil microbial communities affected performance of Astragalus bibullatus, a federally endangered (US) herbaceous legume, in a dual-phase plant-soil feedback study. We used DNA metabarcoding to assess soil microbial communities following an experiment in which A. bibullatus was grown in (1) soils from historically present (HP) and historically absent (HA) sites, and (2) HP and HA soils trained by conspecifics, a co-occurring native congener (A. tennesseensis) and perennial grass (Schizacharium scoparium). Growth experiments demonstrated that A. bibullatus exhibited the greatest growth and nodule production in soils from HP sites and trained by conspecifics and A. tennesseensis. DNA metabarcoding results of phase one showed that HP soils contained a greater abundance of putative mutualists (arbuscular mycorrhizal fungi). In phase two, the nodules of A. bibullatus contained a greater abundance of Alphaproteobacteria when grown in HP soils trained by conspecifics. Additionally, we found that A.bibullatus roots had a higher abundance of AMF fungi when grown in HP soils conditioned by conspecifics, but higher Fusarium pathogens in roots conditioned with HA soils, regardless of plant conditioning. We identified nine Rhizobia taxa unique to HP soils, whereas Fusarium sp. represented the only unique microbial taxon in HA soils. Our results indicate a potentially strong influence of soil microbes on the performance and rarity of A. bibullatus. Understanding the interactions between soil microbes and rare plant species is paramount for developing successful reintroduction programs.

Premise:Genebanks must maintain viable seeds for decades. Seeds that germinate are clearly alive, but some seeds, often from wild populations, do not germinate because they are dormant, empty, aged, or damaged (D.E.A.D.). This work evaluates the effects of D.E.A.D. factors on genebanked seeds using a unique dataset to improve genebanking practices and standards for ex situ conservation of seed collections. Methods:Seeds from over 100 species were recently collected from the same populations as seeds that were genebanked decades ago. Germination proportion and speed were measured after applying various temperature, chemical, or seed coat abrasion treatments. Viability was further tested using vital staining of samples with a low germination proportion. Proportions of dormant, empty, aged, and damaged seeds were compared between seed cohorts. Results:Germination proportion and speed varied among samples, and cues to stimulate germination of dormant seeds were identified for individual species, leading to a positive correlation between viability metrics of germination and vital staining. Empty seeds primarily contribute to low germination in this study. Aging, indicated by lower and slower germination, was evident in several of the stored samples, compared to those that had been recently harvested. Discussion:This unique approach demonstrates the feasibility of genebanking seeds from diverse endangered plant species using freezer storage. Genebanking methods that are more relevant for crop seeds need to be modified when applied to seeds from wild populations because the sample sizes tend to be small and the seeds tend to germinate slowly and asynchronously.

Abstract In degraded ecosystems, soil microbial communities (SMCs) may influence the outcomes of ecological restoration. Restoration practices can affect SMCs, though it is unclear how variation in the onset of restoration activities in woodlands affects SMCs, how those SMCs influence the performance of hard‐to‐establish woodland forbs, and how different woodland forbs shape SMCs. In this study, we quantified soil properties and species abundances in an oak woodland restoration chronosequence (young, intermediate, and old restorations). We measured the growth of three woodland forb species when inoculated with live whole‐soil from young, intermediate, or old restorations. We used DNA metabarcoding to characterize SMCs of each inoculum treatment and the soil after conditioning by each plant species. Our goals were to (1) understand how time since the onset of restoration affected soil abiotic properties, plant communities, and SMCs in a restoration chronosequence, (2) test growth responses of three forb species to whole‐soil inoculum from restoration sites, and (3) characterize changes in SMCs before and after conditioning by each forb species. Younger restored woodlands had greater fire‐sensitive tree species and lower concentrations of soil phosphorous than intermediate or older restored woodlands. Bacterial and fungal soil communities varied significantly among sites. Forbs exhibited the greatest growth in soil from the young restoration. Each forb species developed a unique soil microbial community. Our results highlight how restoration practices affect SMCs, which can in turn affect the growth of hard‐to‐establish forb species. Our results also highlight that the choice of forb species can alter SMCs, which could have long‐term potential consequences for restoration success.

Botanical gardens are addressing urgent biodiversity issues through plant-based capacities including botanical research and data-sharing, conservation horticulture, ecological restoration, seed banking, and more. The Missouri Botanical Garden initiative BiodiverseCity St. Louis, led by the Garden’s sustainability division, adds broad community engagement to this mix. This work includes public and professional education, the demonstration and promotion of ecological landscaping and Green Infrastructure practices, citizen science programs, and coordinating communications for a regional network of partner organizations focused on biodiversity. Diverse activity engages businesses, local governments, elementary and secondary (K-12) schools, colleges, and community groups. Community biodiversity work at the Garden is informed by an institutional core of scientific rigor, provides opportunity for internal collaborations, and aligns with global strategies for plant conservation—to ground impactful local work. Missouri Botanical Garden’s experience offers a model for public gardens: leveraging modes of community engagement, in concert with diverse institutional strengths, to address biodiversity needs.

Abstract Premise Reintroductions or translocations are an increasingly important activity to recover and conserve at‐risk plant species. Yet because many are not published in the scientific literature, learning from previous attempts may often require considerable time and effort. The Center for Plant Conservation Reintroduction Database (CPCRD; https://saveplants.org/reintroduction-database/), a new centralized and standardized repository of U.S.‐based plant reintroductions, aims to improve the efficiency and effectiveness of accessing data on rare plant reintroductions. Methods The CPCRD is the product of multiple efforts to assemble information on rare plant reintroductions in the United States. The database comprises a wealth of standardized data on the key stages of a reintroduction, from the planning and implementation phases, to monitoring and management techniques. Results The CPCRD is a dynamic resource, allowing data contributors to continually update their entries as projects progress. While contributions are ongoing, the CPCRD currently includes 460 projects involving 201 plant taxa, spanning diverse growth forms, ecosystems, and regions. Discussion The CPCRD and its well‐documented and monitored projects provide a valuable practical resource for conservation practitioners, and have supported multiple scientific studies and contributed to the internationally recognized Center for Plant Conservation Best Practices Guidelines.

Between 20 and 40 per cent of plant species are at risk of extinction in the wild worldwide. Conservation translocation is an accepted strategy intended to ensure the conservation of a species in a natural context where it can undergo evolution, usually, but not exclusively, within its historical indigenous range. Because plants are sedentary, practitioners should take care to select an appropriate recipient site, consider the possibility of local adaptation, and choose source material from similar climatic and environmental conditions to the recipient site. As variation increases in a target species’ environment, practitioners should expect greater variation in seed dormancy and timing of germination, and take account of this in the monitoring plan. Prior to translocation, consider the focal species’ dependency on belowground mutualists (e.g. mycorrhizal fungi) and whether recipient sites have appropriate plant-pollinator networks. When selecting founder populations, use as large a founder size as feasible to increase the chance of establishment and survival, and consider the focal species’ life history when choosing propagule stage. If the biology of the focal species is poorly understood and key environmental drivers of translocation success are unknown, use experiments, predictive models, and multiple recipient sites to test hypotheses and improve translocation outcomes. Ensure that threats are known and abated before and after translocation, consider herbivore or predator exclusion, and create a management plan to maintain appropriate habitat conditions or disturbance regimens over the long term. Develop a detailed monitoring and data management plan to track translocated individuals and make sure to account for plant life history, vegetative dormancy, and the potential for lags in next generation seedling recruitment. Translocation success requires long-term commitment, financial and public support, and collaboration among conservation partners.

Spanning nearly two decades, the Pyne’s ground-plum reintroduction programme highlights the need for long-term institutional commitments, experimentation, and follow-through to meet conservation goals. Translocations of other rare plants could similarly benefit from applying adaptive management. When conducted as experiments and placed in an adaptive management framework, failed reintroductions can provide valuable information that can be applied to subsequent reintroductions.

Abstract Seed limitation represents a fundamental constraint to the restoration of native plant communities, and practitioners often apply seed additions to overcome this barrier. However, surprisingly few studies have experimentally tested whether seed additions can increase diversity in herbaceous communities of oak woodlands, which have undergone large‐scale transformation due to logging, altered fire regimes and invasion by non‐native species. Previous studies suggest that structural (thinning of woody biomass) and process‐based (prescribed fire) restoration treatments alone are unlikely to restore the full breadth of taxonomic and functional diversity in the herb layer, which accounts for most species in woodland ecosystems. To explore whether seed additions can improve restoration outcomes in an oak woodland, we sowed high‐diversity seed mixes in paired transects (seeded vs. controls) along a topographic gradient in a degraded site undergoing restoration with non‐native shrub removal, selective tree thinning and prescribed fire. Seed mixes contained native forbs, grasses and sedges from locally sourced material (n = 169 total species) in the regional species pool, and were designed to match species' habitat affinity to appropriate locations along the topographic gradient. The herb flora was sampled pre‐seeding, and for two consecutive years after additions. Seed additions significantly altered community and functional composition, and increased native species richness by 29% (43.0 vs 55.4), and floristic quality by 30% relative to controls. However, fewer than half of the sown species were established 2 years after planting, suggesting that dispersal and establishment limitation are both important barriers to the recovery of the herb flora in oak woodlands. We also tested if species' sown abundance, conservatism or functional group predicted establishment success. Species sown at high abundances and less conservative species recruited the most reliably. Grass and forb establishment rates were more dependent on seeding rate than sedges or legumes, and the mechanisms behind this trend merit further investigation. We found that adding high‐diversity seed mixes in conjunction with non‐native shrub removal, canopy thinning and burning, can accelerate recovery of herbaceous communities in a highly degraded woodland.

Many countries have legislation intended to limit or offset the impact of anthropogenic disturbance and development on threatened plants. Translocations are often integral to those mitigation policies. When translocation is used exclusively to mitigate development impacts, it is often termed a 'mitigation translocation.' However, both the terminology and processes vary regarding interpretation and application, resulting in inconsistent standards, often leading to poorly planned and implemented projects. These mitigation projects rarely achieve the intended 'no net loss' of protected species due to issues with timelines and procedures that result in the mortality of translocated individuals. Instead, such projects are often process driven, focused on meeting legislative requirements which enable the development to proceed, rather than meaningful attempts to minimise the ecological impact of developments and demonstrate conservation outcomes. Here, we propose to reframe mitigation translocations as conservation driven, ensuring best practice implementation and hence, a quantified no net loss for impacted species. These methods include redefining the term mitigation translocation to include conservation objectives and outlining issues associated with the mitigation translocation processes worldwide. We also nominate global standards of practice to which all proposals should adhere, to ensure each project follows a trajectory towards quantified success, with genuine impact mitigation. These proposed standards focus on building efficient translocation plans and improving governance to facilitate a transition from project centred to ecology-driven translocation. Employment of these standards is relevant to development proponents, government regulators, researchers, and translocation practitioners and will increase the likelihood of conservation gains within the mitigation translocation sector.

Native seed vendors are a primary source of germplasm for restoration projects; however, most plant species are not commercially available. Preferences in the types of species that vendors grow and sell may limit the similarity between reference communities and reconstructed ones established from seed mixes. We tested whether a restoration species pool shows preference for certain groups of species, focusing on the Ozark Highland Ecoregion (midcontinent United States). We identified the pool of 1,082 candidate herbaceous plant species appropriate for restoration projects on upland habitats in this region, and then surveyed nine regional seed vendors to assess their commercial availability. Commercially available species were more likely to be forbs over graminoids, perennials over annuals, and common species with larger ranges and moderate conservatism scores. Within forbs, taller species and those with longer bloom durations were favored. Species with affinity to open habitats (e.g. grassland) were more likely to be available from multiple vendors than those from woodlands and forests. Encouragingly, 454 (42%) of the species in this regional pool were available. However, this means that most species in the region are not likely to be included in seed mixes, unless they are hand‐collected from remnant populations. This restoration pool favors common and showy species, which is consistent with previous studies showing these kinds of species tend to dominate seed mixes and restored plant communities. We identified 39 species that were not available from any of the vendors surveyed, which we recommend as candidates for expansion of the Ozark restoration species pool.

The fundamental goal of a rare plant translocation is to create self-sustaining populations with the evolutionary resilience to persist in the long term. Yet, most plant translocation syntheses focus on a few factors influencing short-term benchmarks of success (e.g., survival and reproduction). Short-term benchmarks can be misleading when trying to infer future growth and viability because the factors that promote establishment may differ from those required for long-term persistence. We assembled a large (n = 275) and broadly representative data set of well-documented and monitored (7.9 years on average) at-risk plant translocations to identify the most important site attributes, management techniques, and species' traits for six life-cycle benchmarks and population metrics of translocation success. We used the random forest algorithm to quantify the relative importance of 29 predictor variables for each metric of success. Drivers of translocation outcomes varied across time frames and success metrics. Management techniques had the greatest relative influence on the attainment of life-cycle benchmarks and short-term population trends, whereas site attributes and species' traits were more important for population persistence and long-term trends. Specifically, large founder sizes increased the potential for reproduction and recruitment into the next generation, whereas declining habitat quality and the outplanting of species with low seed production led to increased extinction risks and a reduction in potential reproductive output in the long-term, respectively. We also detected novel interactions between some of the most important drivers, such as an increased probability of next-generation recruitment in species with greater seed production rates, but only when coupled with large founder sizes. Because most significant barriers to plant translocation success can be overcome by improving techniques or resolving site-level issues through early intervention and management, we suggest that by combining long-term monitoring with adaptive management, translocation programs can enhance the prospects of achieving long-term success.

Thinning and removal of woody vegetation is the first step in restoring ecosystem structure to systems altered by woody encroachment. However, pile burning—a common method of eliminating woody residue at restoration sites—can promote the establishment of exotic species and adversely impact soils and native vegetation via extreme soil heating. Despite its widespread use, pile burning effects remain poorly understood in oak woodlands compared to coniferous forests. We examined how pile burning influenced soil properties and herb‐layer recovery in a Midwestern, U.S. oak woodland undergoing restoration via exotic shrub removal, tree thinning, and prescribed burning. We quantified soil properties and passive vegetation recovery inside and adjacent to pile burn scars after 3 years, and tested whether native seed additions in year 1 increased native cover and reduced exotic cover in year 3. Bare ground cover, soil pH, and concentrations of P and Ca remained elevated 3 years after pile burning. In contrast, native cover, native richness, and floristic quality recovered to levels similar to adjacent control locations. Pile burning did not promote exotic invasions, increase inorganic forms of N, or alter patterns of the native cover of most growth forms. However, Carex species failed to reestablish in burn scars. Compared to passive recovery, seed additions increased native cover in burn scars and reduced exotic cover in adjacent control locations. Our results indicate that burn scars can naturally recover in oak woodland, but native seed additions may accelerate this process and improve restoration outcomes.

Resurrecting extinct species is a fascinating and challenging idea for scientists and the general public. Whereas some theoretical progress has been made for animals, the resurrection of extinct plants (de-extinction sensu lato) is a relatively recently discussed topic. In this context, the term 'de-extinction' is used sensu lato to refer to the resurrection of 'extinct in the wild' species from seeds or tissues preserved in herbaria, as we acknowledge the current impossibility of knowing a priori whether a herbarium seed is alive and can germinate. In plants, this could be achieved by germinating or in vitro tissue-culturing old diaspores such as seeds or spores available in herbarium specimens. This paper reports the first list of plant de-extinction candidates based on the actual availability of seeds in herbarium specimens of globally extinct plants. We reviewed globally extinct seed plants using online resources and additional literature on national red lists, resulting in a list of 361 extinct taxa. We then proposed a method of prioritizing candidates for seed-plant de-extinction from diaspores found in herbarium specimens and complemented this with a phylogenetic approach to identify species that may maximize evolutionarily distinct features. Finally, combining data on seed storage behaviour and longevity, as well as specimen age in the novel 'best de-extinction candidate' score (DEXSCO), we identified 556 herbarium specimens belonging to 161 extinct species with available seeds. We expect that this list of de-extinction candidates and the novel approach to rank them will boost research efforts towards the first-ever plant de-extinction.

Successful recovery of populations of endangered plant species requires conservation of existing populations as well as the creation of new populations through reintroduction. However, the ecological requirements of many rare plant species are poorly understood, and many reintroduced populations are unable to survive long term. Effective reintroduction of rare plants, such as the federally endangered Astragalus bibullatus, may depend on developing a greater understanding of the symbiotic relationships that these rare species form with the soil microbiome, as well as determining whether these are species‐ and site‐specific. We inoculated seedlings of A. bibullatus, its more widespread congener A. tennesseensis, and the common grass Schizachyrium scoparium, with soil biota collected from five glade sites where A. bibullatus is historically present (HP) and four glade sites where the species is historically absent (HA). We examined the impacts of soil microbes from HP and HA glade sites as well as from each species on the growth, arbuscular mycorrhizal fungi (AMF) colonization, and formation of root nodules of A. bibullatus and its congener A. tennesseensis. Astragalus bibullatus grew significantly larger when grown in soil from HP glade sites compared to its growth in soil from HA glade sites. Astragalus bibullatus also formed significantly more root nodules when grown in HP soil, but no difference was detected in AMF colonization based on glade history. Our findings suggest that the successful establishment of rare plant species may depend on species‐specific associations with soil mutualists such as nitrogen‐fixing rhizobial bacteria and should consider whether essential microbes are present.

Helianthus eggertii is a rare perennial sunflower of barrens and open habitats in Kentucky, Tennessee, Alabama, and South Carolina in the United States (U.S.). Despite its delisting in the U.S. Endangered Species Act in 2005, little is known about the germination biology of H. eggertii other than seeds require cold stratification for optimal germination. Knowledge about the germination biology of rare species can aid in the management of natural populations and inform strategies for ex situ seed conservation and propagation. We examined how cold stratification, light, and temperature interact to affect seed germination in H. eggertii, and whether germination proportions varied among populations. At the time of maturity in October, seeds have primary physiological dormancy and require cold stratification or prolonged (> 8 wk) incubation in light at cool (15/6 C) temperatures to germinate. Seeds maintained a light requirement for germination when cold stratified in darkness, but not after cold stratification in light. However, seeds germinated to lower proportions after cold stratification in light relative to darkness, and when incubated at temperatures that mimic summer (35/20 C) compared to late spring (25/15 C). Germination varied widely among populations (23-58%), with plants from more open sites exhibiting lower germination proportions than those from partially shaded sites. Our results indicate seeds most likely germinate in early- to mid-spring, and light promotes germination of H. eggertii. Our results highlight the interactive role of light and temperature in determining seed dormancy break and germination in H. eggertii.

Understanding genetic diversity and structure in a rare species is critical for prioritizing both in situ and ex situ conservation efforts. One such rare species is Physaria filiformis (Brassicaceae), a threatened, winter annual plant species. The species has a naturally fragmented distribution, occupying three different soil types spread across four disjunct geographical locations in Missouri and Arkansas. The goals of this study were to understand: (1) whether factors associated with fragmentation and small population size (i.e., inbreeding, genetic drift or genetic bottlenecks) have reduced levels of genetic diversity, (2) how genetic variation is structured and which factors have influenced genetic structure, and (3) how much extant genetic variation of P . filiformis is currently publicly protected and the implications for the development of conservation strategies to protect its genetic diversity. Using 16 microsatellite markers, we genotyped individuals from 20 populations of P . filiformis from across its geographical range and one population of Physaria gracilis for comparison and analyzed genetic diversity and structure. Populations of P . filiformis showed comparable levels of genetic diversity to its congener, except a single population in northwest Arkansas showed evidence of a genetic bottleneck and two populations in the Ouachita Mountains of Arkansas showed lower genetic variation, consistent with genetic drift. Populations showed isolation by distance, indicating that migration is geographically limited, and analyses of genetic structure grouped individuals into seven geographically structured genetic clusters, with geographic location/spatial separation showing a strong influence on genetic structure. At least one population is protected for all genetic clusters except one in north-central Arkansas, which should therefore be prioritized for protection. Populations in the Ouachita Mountains were genetically divergent from the rest of P . filiformis ; future morphological analyses are needed to identify whether it merits recognition as a new, extremely rare species.

First posted May 20, 2021 For additional information, contact: Director, Lower Mississippi-Gulf Water Science CenterU.S. Geological Survey640 Grassmere Park Drive Nashville, TN 37211 The unglaciated southeastern United States is a biodiversity hotspot, with a disproportionate amount of this biodiversity concentrated in grasslands. Like most hotspots, the Southeast is also threatened by human activities, with the total reduction of southeastern grasslands estimated as 90 percent (upwards to 100 percent for some types) and with many threats escalating today. This report summarizes the results of a multistakeholder workshop organized by the Southeastern Grasslands Initiative and the U.S. Geological Survey, held in January 2020 to provide a scientific needs assessment to help inform the Species Status Assessment (SSA) process under the U.S. Endangered Species Act, with a focus on grassland species and communities of conservation concern in the southeastern United States. This report reviews the ecology of southeastern grasslands, including influences on their origin, maintenance, and high species richness and endemism; presents findings from the workshop; and discusses science questions, hypotheses, and possibilities for future research projects to help fill key knowledge gaps.Participants in the January 2020 workshop, representing diverse expertise in various topics in southeastern grassland ecology, were tasked with identifying major threats to grassland species in the Southeast as well as potential ways to make the SSA process more efficient and effective. An underlying assumption and starting place for workshop discussion was that an ecosystem-based approach to the SSA process is more cost-efficient than a species-by-species approach, in large part because many species with similar biological requirements can be addressed by the same actions. Nevertheless, one partner in this effort, the U.S. Fish and Wildlife Service, does require specific attention be given to taxa that have been petitioned for Federal listing, though as often as possible these taxa are considered alongside a larger group of priority taxa with an ecosystem approach.For group discussions, workshop participants followed a modified “World Café” method, a structured conversational approach for knowledge sharing. Group discussions focused on five categories of threats to grassland communities and species: (1) habitat loss, fragmentation, and disruption of functional population connectivity; (2) climate change, especially changes in temperature and precipitation, including intensity and seasonality, and impacts on soil moisture, groundwater levels, and other ecosystem parameters; (3) changes to disturbance regimes, as influenced by climate and land-use change, extinctions, and human attitudes and behaviors; (4) invasive species (not limited to nonnative species); and (5) localized or subregional impacts such as sea-level rise. In addition to group discussions, workshop participants—as well as other grassland experts who were unable to attend the workshop—completed a preworkshop survey concerning challenges and opportunities for grassland conservation. Findings reported here under each of these topics represent ideas, problems, hypotheses, and questions identified by a diverse community of grassland managers and researchers which may be addressed by future research and monitoring in southeastern grassland ecosystems to help guide science-based conservation of grassland-dependent species.