Genetic structure of populations of the red sea urchin, Strongylocentrotusfranciscanus

Population subdivision was evaluated in the red sea urchin, Strongylocentro tus franciscanus, using DNA sequence data from 134 adult individuals collec ted in 1995 and 1996. On average 22 individuals were sequenced from six geo graphic locations between Alaska and Baja California (N = 134), nearly the full extent of the species range. DNA sequence data was obtained from direc t sequencing of a 273 base pair region of the bindin gene, which encodes a sperm fertilization protein. Results indicate that bindin is sufficiently p olymorphic to serve as a genetic marker. We identified 14 unique alleles pr esent in the entire range sampled with a maximum of eight alleles at a spec ific site. Mean pairwise comparison of the 14 unique alleles indicates mode rate sequence diversity (p-distance=1.06). Although there is conflicting ev idence to suggest that Alaska populations may deviate from the Hardy-Weinbe rg expectations, analysis of bindin genotype frequencies indicate that it i s not possible to reject the null hypothesis of random mating throughout th e species range. The results of a chi-square test with pooling conform to H ardy-Weinberg expectations for all populations (P>0.05) except for the Alas ka population (P = 0.037). Inbreeding coefficients are consistent with this result and suggest that for the bindin locus, there is high gene flow. The se results are compared with previously published results of genetic substr ucturing in sea urchins to examine relationships among population structure , dispersal potential and biogeography. (C) 2000 Elsevier Science B.V. All rights reserved.