ALLOZYME AND MITOCHONDRIAL-DNA EVIDENCE OF POPULATION SUBDIVISION IN THE PURPLE SEA-URCHIN STRONGYLOCENTROTUS-PURPURATUS

Despite high potential for dispersal, the purple sea urchin Strongyloc entrotus purpuratus was found to have significant genetic subdivision among locations. Ten geographic locations along the coast of Californi a and Baja California were sampled between 1994 and 1995. Samples from some locations included both adult and recruit urchins. Allozyme anal yses revealed a genetic mosaic, where differentiation over short geogr aphic distances could exceed differentiation over much larger distance s. Significant allozyme differentiation was found among subpopulations of adults (standardized variance, F-ST=0.033), among subpopulations o f recruits (F-ST=0.037), and between adults and recruits from the same location. DNA-sequence data for the mitochondrial cytochrome oxidase I gene also showed significant heterogeneity among locations, with a m ild break in haplotype frequencies observed similar or equal to 300 km south of Point Conception, California. Repeated sampling over time is necessary to determine whether these patterns of differentiation are stable and to begin to understand what forces produce them.