Weak phylogeographic structure in the endemic western North American fairy shrimp Branchinecta lynchi (Eng, Belk and Erickson 1990)

The vernal pool fairy shrimp (Branchinecta lynchi) (Eng et al. in J Crustac Biol 10:247-277, 1990) is broadly distributed throughout California's Central Valley with disjunct populations in southern California and southern Oregon. A survey of genetic variation at the mitochondrial cytochrome c oxidase subunit I (COI) gene was conducted from individuals collected throughout the range of the species. Phylogenetic analysis of unique haplotypes could not resolve any significant genetic partitions below the species level. A detailed analysis of samples from two pools indicates that sample sizes underestimate overall variation, but that the general phylogeographic pattern still holds. Evidence was found for a putative long-distance dispersal event between Central Valley sites and the Oregon site. These results indicate that geographically limiting stochastic colonization followed by local diversification may be important in governing current genetic structure for this species. Future and current conservation/restoration efforts should recognize the geographic limitations to population structure for this species and focus on local endemic genetic variation.