Mitochondrial DNA variation of the west-coast rock lobster, Jasus lalandii: marked genetic diversity differences among sampling sites

Jasus lalandii (Milne-Edwards 1837), thewest-coast rock lobster, occurs in the shallow, cool-temperate waters along the south and west coasts of southern Africa. This species has a long history of intensive exploitation, which has had a significant impact on population numbers in the past. To enhance our current understanding of lobster population structuring, genetic data from the mitochondrial (mt) DNA 16S rRNA gene was generated for 235 adult individuals collected at eight sampling sites. Most individuals (59.6%) share a common haplotype and 35 unique haplotypes were dispersed throughout the range. In total, 97.2% of the variation was found among individuals within sampling sites and 2.8% was among sites. Pairwise Phi(ST) analyses revealed shallow, yet significant structure between Hout Bay individuals and some other sampling sites. The J. lalandii haplotype network indicates a starlike structure with no geographic signal; however, genetic diversity sharply decreases towards the edges of the species distribution. The general lack of phylogeographic structure among J. lalandii populations probably results from the absence of strong barriers to larval dispersal. Based on our mtDNA data there is no justification for the recognition of separate fishing stocks, but the high genetic diversities of populations at Hout Bay and Cape Hangklip, the latter currently outside of marine protected areas, makes these populations critical to conservation efforts.