Microsatellite Analysis of the Population Structure in the Santa Ana Speckled Dace (Rhinichthys osculus): Evolution and Conservation

Rhinichthys osculus, the Speckled Dace, is one of the most ubiquitous fish in western North America. The local taxon within Southern California is known as the Santa Ana Speckled Dace (SASD). The purpose of this study was to identify polymorphic microsatellite markers for R. osculus in which twenty-three were identified. Seven of these loci were used to examine the patterns of genetic variation and population structure that occurs within and among the watersheds in Southern California. The study also examined the regional relationships among Southern California, Central California and Owen’s River dace. Preliminary analysis revealed that moderate levels of population structure exist within the Southern California region; and that greater geographic structuring exists among the watersheds of Southern California, Central Coast and Owen’s River regions that are congruent with the regional differentiation elucidated by mtDNA sequence data.  Utilizing this information we were able gain a better understanding of the evolutionary relationships among the Southern California populations of SASD, and how this geographic region is related to other regions in California. SASD populations have been extirpated due to habitat fragmentation.  We hope this study will guide the strategies for conservation of the remaining populations of SASD and watershed management in California.