Jepsonia malvifolia (Saxifragaceae) is a long-lived perennial herb endemic to the Channel Islands of southern California and Guadalupe Island, Mexico. Twelve populations of J. malvifolia on San Clemente Island were surveyed for their genotype at 21 allozyme loci, revealing high levels of genetic polymorphism. For all individuals across San Clemente Island, 95.2% of loci are polymorphic with AP = 2.90 and HE = 0.179. Populations averaged 60.2% polymorphic loci with AP = 2.42 and HE = 0.158. Most variation is found within rather than among populations (GST = 0.101) although differentiation among populations is significant. Genetic identities range from 0.936 to 0.999 with mean I = 0.975. There is no significant relationship between genetic and geographic distance. Gene flow among populations is Nm = 9.5 based on private alleles and Nm = 2.2 based on FST. Outcrossing rates based on fixation indices average t = 0.753, indicating a primarily outcrossed mating system. The genetic variation observed is unusually high for an insular endemic herb and indicates that J. malvifolia is unlikely to be endangered by genetic factors.

Key words: allozymes, conservation, endemic, genetic variation, Jepsonia, Saxifragaceae