Isolation of microsatellite markers in a chaparral species endemic to southern California, Ceanothus megacarpus (Rhamnaceae)(1)

• Premise of the study: Microsatellite (simple sequence repeat [SSR]) markers were developed for Ceanothus megacarpus, a chaparral species endemic to coastal southern California, to investigate potential processes (e.g., fragmentation, genetic drift, and interspecific hybridization) responsible for the genetic structure within and among populations distributed throughout mainland and island populations. • Methods and Results: Four SSR-enriched libraries were used to develop and optimize 10 primer sets of microsatellite loci containing either di-, tri-, or tetranucleotide repeats. Levels of variation at these loci were assessed for two populations of C. megacarpus. Observed heterozygosity ranged from 0.250 to 0.885, and number of alleles ranged between four and 21 per locus. Eight to nine loci also successfully amplified in three other species of Ceanothus. • Conclusions: These markers should prove useful for evaluating the influence of recent and historical processes on genetic variation in C. megacarpus and related species.