Phylogeography Of Leptasterias aequalis Near Terrestrial Runoff Sources in the San Francisco Bay Area

The small six-rayed seastar, Leptasterias spp., forms a cryptic species complex commonly found in the rocky intertidal zone from Alaska to southern California (Flowers & Foltz, 2001).While the majority of sea stars have a planktonic larval stage, Leptasterias spp. brood their larvae and after direct development, the young crawl away. Their limited dispersal abilities suggest establishments of semi-isolated populations, where adaptation to local conditions may occur. To gain insight into the population structure Leptasterias spp. it is necessary to compare their genetic patterns to population abundance and local environmental features, specifically terrestrial runoff into the ocean. We hypothesize that local populations at sites separated by freshwater flow or urban runoff will have similar genetic patterns with other sites that contain a runoff barrier between populations. Two-hundred and fifteen Leptasterias spp. samples have been collected from eight sites with nearby outlets. Oceanic and anthropogenic features of habitat extremes have been categorized between sites in central California including Sonoma, Marin, San Francisco and San Mateo counties. Genetic variation is currently being examined with 300 base pair fragments of the mitochondrial control region, known as D-Loop, to estimate genetic variation using a FST-value.  Genetic data will be compared to recruitment data and the categorized habitat features to investigate whether the haplotypes shared among sites depends on the barrier between the locations. The results will help us map the distribution of Leptasterias spp. within the cryptic species complex and the distribution of their genotypes around sources of terrestrial runoff.