Genetic diversity and reproductive biology in Warea carteri (Brassicaceae), a narrowly endemic Florida scrub annual

Carter's mustard (Warea carteri) is an endangered fire-stimulated annual en demic of the Lake Wales Ridge, Florida, USA. This species is characterized by seed banks and large fluctuations in plant numbers, with increases occur ring in postdisturbance habitat. We investigated the mating system, pattern s of isozyme variation, and effective population sizes of W. carteri to bet ter understand its population biology and to comment on reserve designs and management proposals relevant to this species. Waren carteri is self-compa tible and autogamous, and probably largely selfing. Measures of genetic var iation in W. carteri were lower than values reported for species with simil ar ecological and life history traits (6.6% of loci polymorphic within popu lations, 1.87 alleles per polymorphic locus, and 0.026 and 0.018 expected a nd observed heterozygosity, respectively). The high average value for Nei's genetic identity (0.989) reflects the paucity of genetic diversity. Geneti c variation within populations was not correlated with aboveground populati on size. effective population size estimates (N-e), or recent disturbance h istory. Much of the diversity detected was found among populations (F-ST = 0.304). A significant cline in allele frequencies at one locus and a signif icant negative correlation between geographic distance and Nei's genetic id entity also point to spatial organization of generic diversity. As a result we propose that reserve design should include the entire geographic range of W. carteri. We also recommend that the natural fire regime be mimicked.