Population genetics of black abalone, Haliotis cracherodii, along the central California coast

over the past three decades, the black abalone, Haliotis cracherodii, has e xperienced precipitous declines in abundance over portions of its range in southern and central California. The potential for recovery of these popula tions is dependent in part on dispersal processes; that is, can distant pop ulations serve as sources of recruits to locales that no longer harbor H. c racherodii? Here we use population genetic analysis to assess levels of pop ulation subdivision and infer recruitment processes. Epipodial tissue sampl es were obtained from over 400 black abalone from seven geographic sites be tween Santa Cruz and Santa Barbara counties in central California. Allelic frequencies were determined for each population at three polymorphic enzyme -encoding loci (GPI, AAT-I and PGM). Significant allelic frequency differen tiation among sites was observed at all three loci. Genetic distance was fo und to be independent of geographic distance over the approximately 300-km sampling range. In addition, a limited number of DNA sequences (total N = 5 1) were obtained for the mitochondrial cytochrome oxidase subunit I gene (C OI) from five of the populations. Since the same common COI haplotype domin ated each population, this analysis had little statistical Dower and failed to detect population structure. The observed level of population different iation at allozyme loci was three-fold higher than that observed in Califor nia red abalone, H. rufescens. The species differ in their breeding period and it is suggested that the relatively short, summer. breeding season of b lack abalone limits dispersal because larvae experience reduced valiance in oceanographic conditions relative to red abalone that spawn year-round. Ba sed on these results, rates of recolonization and recovery of locally depre ssed or extirpated black abalone populations are likely to be slow despite harvest restrictions. (C) 2000 Elsevier Science B.V. All rights reserved.