Euphorbia Telephioides (Euphorbiaceae)
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Genetic diversity within a threatened, endemic North American species, Euphorbia telephioides (Euphorbiaceae) Dorset W. Trapnell, J. L. Hamrick & Vivian Negrón-Ortiz Conservation Genetics ISSN 1566-0621 Conserv Genet DOI 10.1007/s10592-012-0323-4 1 23 Your article is protected by copyright and all rights are held exclusively by Springer Science+Business Media B.V.. This e-offprint is for personal use only and shall not be self- archived in electronic repositories. If you wish to self-archive your work, please use the accepted author’s version for posting to your own website or your institution’s repository. You may further deposit the accepted author’s version on a funder’s repository at a funder’s request, provided it is not made publicly available until 12 months after publication. 1 23 Author's personal copy Conserv Genet DOI 10.1007/s10592-012-0323-4 RESEARCH ARTICLE Genetic diversity within a threatened, endemic North American species, Euphorbia telephioides (Euphorbiaceae) Dorset W. Trapnell • J. L. Hamrick • Vivian Negro´n-Ortiz Received: 23 September 2011 / Accepted: 20 January 2012 Ó Springer Science+Business Media B.V. 2012 Abstract The southeastern United States and Florida which it occurs, Gulf (0.084), Franklin (0.059) and Bay support an unusually large number of endemic plant spe- Counties (0.033), were also quite low. Peripheral popula- cies, many of which are threatened by anthropogenic tions did not generally have reduced genetic variation habitat disturbance. As conservation measures are under- although there was significant isolation by distance. Rare- taken and recovery plans designed, a factor that must be faction analysis showed a non-significant relationship taken into consideration is the genetic composition of the between allelic richness and actual population sizes. Our species of concern. Here we describe the levels, and par- data suggest that E. telephioides populations were probably titioning, of genetic diversity in 17 populations of the rare more continuously distributed in Bay, Gulf and Franklin and threatened Florida endemic, Euphorbia telephioides Counties and that their relative contemporary isolation is a (telephus spurge). Species-wide genetic diversity was high recent phenomenon. These results are important for (Ps = 91%, APs = 3.81, As = 3.57 and Hes = 0.352) as developing a recovery plan for this species. was mean population genetic diversity (Pp = 81%, APp = 2.98, Ap = 2.59 and Hep = 0.320) which ranks it among Keywords Allozymes Á Conservation Á Florida Á the highest 10% of plant species surveyed. Partitioning of Recovery Á Southeastern United States Á Telephus spurge genetic variation (Gst = 0.106) was low compared to other herbaceous outcrossing perennials indicating high histori- cal gene flow across its limited geographic range. Among Introduction population Gst values within the three Florida counties in The southeastern United States harbors an unusually large number of endemic plant taxa (Delcourt and Delcourt 1991) with approximately 385 species endemic to Florida alone (Gentry 1986). Many of these species are now threatened by anthropogenic habitat loss and degradation D. W. Trapnell (&) Á J. L. Hamrick related to factors such as urbanization, habitat conversion, Department of Plant Biology, University of Georgia, invasive species, fire suppression and/or alteration of nat- 30602 Athens, Georgia e-mail: [email protected] ural fire regimes (Slapcinsky et al. 2010). The value and importance of at risk species, and the need to protect them, D. W. Trapnell are increasingly being recognized. For the conservation and Odum School of Ecology, University of Georgia, recovery of such species in their native habitat to be 30602 Athens, Georgia effective, a multi-faceted approach is necessary that V. Negro´n-Ortiz includes habitat management and protection, studies of the U.S. Fish and Wildlife Service, Panama City, FL 32405, USA species’ life history characteristics and interactions with other organisms (e.g., pollinators and seed dispersers), and V. Negro´n-Ortiz Department of Botany, Miami University, Oxford, estimates of their genetic diversity. Species with more OH 45056, USA genetic variation are more likely to have the capacity to 123 Author's personal copy Conserv Genet adapt to biotic or abiotic fluctuations in their environ- Materials and methods ment (Fisher 1930; Dobzhansky 1937) such as novel pathogens, climate change, etc. Thus, preservation of a Study species species’ genetic diversity is a factor that should improve its chances of surviving over evolutionary time. In this con- Euphorbia L. (Euphorbiaceae), commonly called spurge, is text, knowledge of the levels and distribution of genetic diverse worldwide, and consists of about 1,600 annual or variation within species of conservation concern, and the perennial herbaceous, woody shrub, or tree species (Nar- identification of populations with the greatest evolutionary bona et al. 2002). There are approximately 107 Euphorbia potential, are essential for the development of effective spp. native to the United States and Canada (http://www. conservation and recovery practices. As an example of how invasive.org/eastern/biocontrol/14LeafySpurge.html). The such knowledge can be applied, populations with rare genus is currently divided into five subgenera (Webster alleles or with elevated levels of genetic diversity may be 1967) and several sections and subsections (Bridges and given higher priorities for preservation than less genetically Orzell 2002). Within subsection Inundatae, five Euphorbia diverse and unique populations. Plants from the most taxa are currently recognized as endemic to areas ranging genetically diverse populations would also be the most from southern Georgia to southern Florida, with some valuable propagule sources for recovery projects. Thus, extending west to southern Mississippi (Bridges and Orzell direct empirical data regarding the levels and partitioning 2002). All are adapted to recurrent natural fires and are of genetic variation are of fundamental importance before found on sandy outer coastal plain ridges that date to the effective conservation decisions can be made. This is Pleistocene, Pliocene, or Miocene (Bridges and Orzell particularly true of species with small, isolated populations 2002). One of these five taxa is the perennial herb which is a pattern that currently characterizes many Euphorbia telephioides Chapman (telephus spurge) of endemic plant taxa. northwest Florida. Euphorbia telephioides Chapman (telephus spurge), This species is ephemeral; it can be abundant at newly which is restricted to the Florida panhandle, is a south- disturbed sites but often is completely absent when sites eastern endemic with endangered world status in the 1997 are revisited a few years later. Even if shoots are not IUCN Red List of Threatened Plants (Walter and Gillett present, plants may persist as large tuberous roots, which 1998). It was also designated as threatened in the Federal help individuals survive harsh conditions and distur- Register, May 8, 1992 (designation effective June 8, 1992; bances. Frequent prescribed fire regimes are important for 50 CFR Part 17 1992). A recovery plan was approved in maintenance of flatwoods diversity (Hiers et al. 2007), and June 1994 (USFWS 1994). The 2008 U.S. Fish and where fire management is implemented, healthy stable Wildlife Service 5 Year Review of E. telephioides reports populations of E. telephioides are maintained (USFWS that nine locations appear to have been extirpated by 2007). Euphorbia telephioides is restricted to Bay, Gulf, development and/or habitat modification during the and Franklin counties in Florida (Fig. 1). It is unknown 5 years prior to the report. Habitat modification was the whether E. telephioides was once continuously distributed primary threat identified in the recovery plan and remains throughout the three counties or whether populations have the prime issue; specific threats are real estate develop- always been patchily distributed. Currently populations ment and habitat conversion to pine plantations with are localized and separated by clear cuts, pine plantations accompanying mechanical vegetation destruction and soil or residential/commercial development. At present the disruption. The species was assigned a recovery priority species occurs in about 40 locations, all within 7 km of number of 2C, which indicates a species with high threat the Gulf of Mexico. Patch sizes are highly variable of extinction due to habitat destruction, but with high ranging, from 20 to [3,000 individuals/population recovery potential. With the goal of preserving the species (Table 1). Nearly half of the populations occur on public as a whole, our objective is to estimate the levels and lands with many remaining populations persisting on distribution of genetic diversity within and among popu- private timberland and utility rights-of-way (USFWS lations of E. telephioides distributed throughout its current 2007). Within this restricted range, E. telephioides occurs native range. Our specific questions: (1) Are there sig- in xeric to mesic pine flatwoods and in scrubby pinelands nificant differences in genetic diversity within and among dominated by Aristida stricta (wiregrass) and/or Pinus populations of E. telephioides? (2) Is genetic similarity palustris (longleaf pine) or P. elliottii (slash pine). among populations a function of spatial distances sepa- Uncommonly, E. telephioides grows in wetlands with rating them? (3) Is genetic diversity within populations