Systematics Section / ASPT
Derieg, Nathan , Bruederle, Leo P. .
Population genetic implications of post-glacial migration in Carex cryptolepis (Cyperaceae).
CAREX cryptolepis Mack. (Cyperaceae) is a widespread endemic distributed across northeastern North America. Except for a small number of marginal populations, the range of this species was covered by the Laurentide ice sheet during the Wisconsin Glaciation. Carex cryptolepis is an early successional species occupying open wet areas with acidic sandy or organic soils and low levels of calcium. To determine the impact of postglacial migration on genetic diversity within and among populations of C. cryptolepis we performed starch gel electrophoresis and allozyme analysis. For 346 individuals from ten populations, eighteen putative loci were resolved, of which five were polymorphic (27.8%) — only five populations were variable, the remainder were fixed at all loci. Measures of genetic diversity averaged across populations in C. cryptolepis (P = 3.89; Ap = 2.00; He = 0.007) were low relative to other caespitose carices (P = 14.15; Ap = 2.06; He = 0.043), as well as the putative sister taxon C. lutea LeBlond (P = 21.11; Ap = 2.15; He = 0.051). Statistically significant deviations from Hardy-Weinberg Equilibrium were correlated with large positive fixation indices. Mean inbreeding within populations (f = 0.49) was similar to that observed in C. lutea (f = 0.44). Populations were highly differentiated (FST = 0.855) relative to other caespitose carices (GST = 0.412) and C. lutea (FST = 0.404). Though limited sampling of broadly distributed species can inflate observed levels of population differentiation, the large FST of C. cryptolepis may also reflect limited gene flow among populations established after the last glacial maximum (LGM). Decreased levels of genetic diversity and heightened population differentiation are considered a general consequence of postglacial range expansion from refugial populations; determining the pattern of postglacial migration in C. cryptolepis will require sampling additional populations.
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1 - University of Colorado at Denver and Health Sciences Center, Biology, Campus Box 171, P.O. Box 173364, Denver, Colorado, 80217, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Wednesday, August 2nd, 2006
Time: 1:15 PM