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Genetic Diversity and Reproductive Biology in Warea Carteri (Brassicaceae), a Narrowly Endemic Florida Scrub Annual Author(S): Margaret E

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Genetic Diversity and Reproductive Biology in Warea Carteri (Brassicaceae), a Narrowly Endemic Florida Scrub Annual Author(S): Margaret E Genetic Diversity and Reproductive Biology in Warea carteri (Brassicaceae), a Narrowly Endemic Florida Scrub Annual Author(s): Margaret E. K. Evans, Rebecca W. Dolan, Eric S. Menges, Doria R. Gordon Source: American Journal of Botany, Vol. 87, No. 3 (Mar., 2000), pp. 372-381 Published by: Botanical Society of America Stable URL: http://www.jstor.org/stable/2656633 . Accessed: 22/10/2011 09:41 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Botanical Society of America is collaborating with JSTOR to digitize, preserve and extend access to American Journal of Botany. http://www.jstor.org AmericanJournal of Botany 87(3): 372-381. 2000. GENETIC DIVERSITY AND REPRODUCTIVE BIOLOGY IN WAREA CARTERI (BRASSICACEAE), A NARROWLY ENDEMIC FLORIDA SCRUB ANNUAL1 MARGARET E. K. EVANS,25 REBECCA W. DOLAN,3 ERIC S. MENGES,2 AND DORIA R. GORDON4 2ArchboldBiological Station,PO. Box 2057, Lake Placid, Florida 33862 USA; 3FriesnerHerbarium, Butler University,Indianapolis, Indiana 46208 USA; and 4The Nature Conservancy,Department of Botany,PO. Box 118526, Universityof Florida, Gainesville, Florida 32611 USA Carter's mustard(Warea carteri) is an endangered,fire-stimulated annual endemic of the Lake Wales Ridge, Florida, USA. This species is characterizedby seed banks and large fluctuationsin plant numbers,with increases occurringin postdisturbancehabitat. We investigatedthe matingsystem, patterns of isozyme variation,and effectivepopulation sizes of W. carteri to betterunderstand its populationbiology and to commenton reservedesigns and managementproposals relevant to this species. Warea carteriis self-compatibleand autogamous,and probablylargely selfing. Measures of geneticvariation in W. carteri were lower than values reportedfor species with similar ecological and life historytraits (6.6% of loci polymorphicwithin populations, 1.87 alleles per polymolphiclocus, and 0.026 and 0.018 expected and observed hetero- zygosity,respectively). The high average value for Nei's genetic identity(0.989) reflectsthe paucity of genetic diversity. Genetic variationwithin populations was not correlatedwith aboveground population size, effectivepopulation size estimates (Ne), or recentdisturbance history. Much of the diversitydetected was foundamong populations(FST = 0.304). A significant cline in allele frequenciesat one locus and a significantnegative correlation between geographic distance and Nei's genetic identityalso point to spatial organizationof geneticdiversity. As a resultwe propose thatreserve design should include the entiregeographic range of W. carteri. We also recommendthat the naturalfire regime be mimicked. Key words: Brassicaceae; effectivepopulation sizes; genetic diversity;mating system; Warea carteri. The Lake Wales Ridge (LWR; Highlands and Polk one of seven LWR endemics forwhich we are gathering Counties) of south-centralFlorida is both a hotspot of detailed geneticand demographicdata to evaluate current biodiversityin the continentalUnited States and highly reserve designs and make recommendationsabout fire endangered (Noss and Peters, 1995). Among higher management. plants, there are 16 federallylisted species endemic to Warea carteriis a federallyendangered annual occur- the LWR. The ongoingcreation of an archipelagoof fire- ringin xeric sandhillsand scrubbyflatwoods (community managed reserve "islands" is key to theirconservation. delineationsfollow Abrahamson, 1984). There are his- Designinga reservesystem and land managementprogram torical records of W. carteri fromoutside the LWR, in- that will supportviable populations or metapopulations cluding Brevard, Broward, Dade, De Soto, and Glades of these species requires knowledge of theirautecology Counties (Al-Shebaz, 1985). In his descriptionof the spe- and populationstructure. Warea carteri (Brassicaceae) is cies, Small (1909) stated that W. carteri was the "most common species of Warea, occur[ring]in great abun- 1 Manuscriptreceived 25 August 1998; revision accepted 24 June dance." Warea carteri has almost certainlybeen extir- 1999. The authors thank Butler undergraduatestudents Halle McKinney, pated fromthese areas, indicatingit has already suffered Aaron Mast, Bill Thornberg,Jennifer Copeland, and Matt Halfhill for a reductionin its range. The xeric communitiesof the assistance in conducting the electrophoresis;Dawn Berry, Deborah LWR were historicallydistributed in over 200 patches Graves, Stacey Halpern, Nancy Kohfeldt,George Landeman, Marina rangingin area fromfour to 1200 hectares(ha) along the Morales-Hernandez,Pedro F Quintana-Ascencio,Joyce Voneman, and -160 X 20 km north-southridge (Christman,1988). Per- Rebecca Yahr forfield assistance at ArchboldBiological Station(ABS); The NatureConservancy's staff, including Geoff Babb, Steve Mol-rison, oni and Abrahamson (1985) estimatedthat 84% of the Bea Pace, and Steve Shattlerfor help withcollecting census data at the presettlementextent of xeric, upland communities in Tiger Creek Preserve; Rebecca Yahr for organizingthe leaf sampling; Highlands County (which contains close to half the Pedro F Quintana-Ascenciofor assistance withnested ANOVAs; Russ LWR) had been convertedto citrusgroves or residential Lande for his recommendationsregarding the effectivepopulation size developmentsby 1981. methodology;Scott Bergen forcreating Figures 1 and 4; and Christine V. Hawkes, Lucinda McDade, Michael Nachman,D. Lawrence Venable, Demographic data indicate thatW. carterithrives in a and Pedro F Quintana-Ascenciofor helpful commentson the manu- temporallyrestricted, postdisturbance niche (Menges and script.This work was fundedby The NatureConservancy's Ecosystem Gordon, 1996). Large fluctuations(up to threeorders of Research Program,the Florida Chapterof The NatureConservancy, the magnitude)in the numberof plants are associated with Florida Division of Forestry,Archbold Biological Station (ABS), and fire,with increases the year afterfire followed by de- Butler University. 5Author forcorrespondence, current address: Departmentof Ecology creases the second year afterfire (Menges and Gordon, and EvolutionaryBiology, Biological Sciences West, Room 310, Uni- 1996). Oscillations in 2-yr cycles oftenoccur, damping versityof Arizona, Tucson, Arizona 85721 USA (520-621-4022). over time. Warea carteri may appear to be extirpated 372 March 2000] EVANS ET AL.-GENETICS AND ECOLOGY OF AN ENDANGERED ANNUAL 373 fromsites for years, only to have abovegroundindivid- uals recruitafter fire. Sites associated withanthropogenic disturbanceoften support more stable and persistentbut small populations. Historically,fires were frequentin peninsular Florida. Estimates of the natural fire return . 4 v : S :- intervalsof the communitiesW. carteri inhabitsspan 2- 20 yr,based on the life historiesof plants in these com- munitiesand theirpatterns of abundance in response to fire(Abrahamson and Hartnett,1990; Myers, 1990; Os- tertagand Menges, 1994; Menges and Kohfeldt, 1995; Menges and Hawkes, 1998). Fires have now been sup- pressed on the LWR for -60 yr. Orangc The ephemeralnature of populationsof W. carterisug- Osceola gests that seed banks are present.Seed dormancyof at least 2 yr has been demonstratedunder laboratorycon- ditions(N. Kohfeldtand E. Menges, ArchboldBiological Station [ABS], unpublisheddata). Fruitsand seeds of W. carterido not have any specialized structuresto facilitate dispersal, and spatial congruenceof abovegroundpopu- lations over time suggests limiteddispersal (E. Menges, ABS, personalobservations). Seeds of W. carteriaverage 0.282 ? 0.067 mg, and theirpotential horizontal travel is 1.89 m in a wind speed of 2.17 m/s(D. Gordon, The Nature Conservancy [TNC], unpublisheddata). Conservation of genetic diversityis considered to be .~~~~~~ S. importantfor the long-termevolutionary potential of spe- cies (Barrettand Kohn, 1991; Huenneke, 1991). The pri- marypurpose of thisstudy was to assess geneticdiversity in W. carteri, by surveyingisozymes in 23 populations throughoutthe species' range (Fig. 1), and make rec- ommendationsabout how to capturethis diversityin re- serves. Since genetic diversityis a dynamic,not a static phenomenon,we assessed processes and traitsthat might affect the population genetics of W. carteri. Using Wright'sF statistics,we assessed populationsubstructure and gene flow.Since the matingsystem of W. carteriwas unknown and likely to influencepatterns of genetic di- versity(Loveless and Hamrick,1984; Hamrickand Godt, 1990), we determinedthis traitand discuss its implica- tions for demographicand genetic dynamics. Given the large fluctuationsof populationswith fire and persistence between fires via in situ seeds, we estimatedeffective populationsizes of W. carteri and relatepopulation-level genetic diversitystatistics with census population sizes, effectivepopulation sizes, and recenthistory of disturbance. Thus our approach to the conservationof W. carterihas been to obtain genetic,ecological, and demographicdata to reconstructthe dynamics of past and presentpopula- tions and evaluate reserve designs and firemanagement regimesthat will affectpopulation dynamics and genetic ,.,V.,V variationin
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