Helenurm, Kaius , Brandsrud, Michelle , McGlaughlin, Mitchell E .
High levels of microsatellite differentiation in adjacent populations of the endangered, insular endemic Sibara filifolia.
Sibara filifolia (Brassicaceae) is a diminutive annual that was presumed extinct until it was rediscovered on San Clemente Island, California, in 1986. It is currently known from several small populations within 700m of each other, and from occasional scattered individuals nearby. We surveyed genetic variation in five populations using nine polymorphic microsatellite loci. Populations contain low levels of genetic variation, with only one to four polymorphic loci per population and expected heterozygosities ranging from HE=0.007 to HE=0.032. Four of the populations are very similar to one another (pairwise FST < 0.045); the remaining population, which is 300m downslope, is fixed for rare alleles at five loci and is significantly different from the other populations (pairwise FST = 0.946 to FST = 0.971, P < 0.0001). Bayesian assignment tests and estimates of gene flow both indicate that the five populations group into two genetic clusters. The low levels of within-population variation and the relatively high differentiation of one population relative to the others, despite their close proximity, is likely to be primarily due to genetic drift in small populations. Inbreeding and limited seed dispersal may be secondary factors accentuating genetic drift in these small, adjacent populations.
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1 - University of South Dakota, Department of Biology, 414 E. Clark St, Vermillion, SD, 57069, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Williford A/Hilton
Date: Tuesday, July 10th, 2007
Time: 8:30 AM