Genetic Differentiation of Geographically Marginal Populations in Carex mitchelliana (Cyperaceae): Implications for Conservation

Abstract

BRUEDERLE, L.P. (Department of Biology, Campus Box 171, University of Colorado at Denver, PO. Box 173364, Denver, CO 80217-3364). Genetic differentiation of geographically marginal populations in Carex mitchelliana (Cyperaceae): Implications for conservation. J. Torrey Bot. Soc. 126:1-8. 1999.-Carex mitchelliana M.A. Curtis, a historically rare plant species, is known from fewer than 100 populations in the eastern and southeastern United States. To ascertain the extent and distribution of genetic variability within this taxon, ten populations distributed from New York to Alabama were characterized by starch gel electrophoresis coupled with substrate specific staining and allozyme analysis. Patterns of variation observed resembled those previously described for the entire Carex crinita Lam. species complex. Values obtained for several parameters of population genetic structure (e.g., percentage polymorphic loci) suggest that Carex mitchelliana is more variable than the other taxa in this species complex despite its restricted distribution and lower abundance. Nei's unbiased genetic identity and gene diversity analysis revealed genetic divergence between Gulf State and geographically marginal Atlantic Coastal Plain populations; although harboring less genetic diversity, Atlantic Coastal Plain populations were differentiated for alleles unique to this species at two loci. Preservation of genetic diversity in this taxon requires maintenance of that component attributable to genetic differences observed among populations, as well as between the two geographic regions. Populations from throughout the distribution of this taxon including both regions, should be preserved.