HELENURM, KAIUS* and SARAH HELM. Department of Biology, University of South Dakota, Vermillion, SD 57069. - High levels of genetic differentiation in the endangered insular endemic Sibara filifolia (Brassicaceae).
Sibara filifolia (Brassicaceae) is a diminutive annual that was
presumed extinct until it was rediscovered on San Clemente Island in
1986. It is known from populations on three adjacent ridges within
150m of each other, and from occasional scattered individuals nearby.
Electrophoretic data for 29 allozyme loci indicate low overall levels
of genetic variation, with only two polymorphic loci and low
heterozygosity (HE=0.009). However, all polymorphism
occurred in just one of the three populations, resulting in
significant differentiation among populations (FST=0.145).
Surveys of genetic variation using more than 20 polymorphic RAPD
markers revealed a similar level of differentiation among populations
(FST=0.159). The relatively high differentiation among
populations, despite their close proximity, may be due to inbreeding,
limited seed dispersal, and small population size.
Key words: allozymes, conservation, endemic, genetic differentiation, genetic diversity, RAPDs