Deprenger-Levin, Michelle , Bruederle, Leo P. .
High genetic diversity in a rare North American endemic, Carex scirpoidea ssp. convoluta.
ONLY 6% of all flowering plant species are dioecious, a breeding system that is believed to have evolved independently numerous times and can be expected to alter levels of genetic diversity through obligate outcrossing. Starch gel electrophoresis coupled with allozyme analysis was used to quantify genetic diversity in the dioecious sedge Carex scirpoidea ssp. convoluta (Kükenthal) Dunlop, which was interpreted within the context of the life history, geographic distribution, and recent evolutionary history of this rare, narrow endemic and its more widespread conspecific C. scirpoidea Michx. ssp. scirpoidea. Carex scirpoidea ssp. convoluta is a Great Lakes endemic found in Michigan and Ontario. This taxon is threatened, being restricted in distribution to prairie pavement barrens, a globally rare community occupying exposed limestone bedrock. Twenty-two loci were resolved for three populations of C. scirpoidea ssp. convoluta sampled from the Lake Huron shoreline on Drummond Island and the lower peninsula of Michigan. Genetic diversity averaged across populations (P = 35.35; Ap = 2.47; He = 0.145) was much higher than has been reported for other caespitose carices (P = 14.15; Ap = 2.06; He = 0.043), being more similar to rhizomatous carices (P = 41.93; Ap = 2.23; He = 0.1796). In contrast, Colorado populations of C. scirpoidea ssp. scirpoidea revealed only a modest level of diversity (P = 20.00; Ap = 2.17; He = 0.068), possibly the result of isolation through disjunction. Significant deviations from Hardy-Weinberg expectations were correlated with heterzygote deficiencies. Populations of Carex scirpoidea ssp. convoluta are poorly differentiated (FST = 0.232) relative to other caespitose carices (GST = 0.412), presumably due to high levels of gene flow. Despite its caespitose habit, limited range, and recent post-glacial evolutionary history, obligate outcrossing appears to be maintaining genetic diversity in this threatened subspecies.
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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: Array
Date: Monday, July 31st, 2006
Time: 10:45 AM