Mitochondrial DNA variation in spiny lobster Palinurus delagoae suggests genetically structured populations in the southwestern Indian Ocean

The spiny lobster Palinurus delagoae inhabits the deep shelf waters and oceanic ridges of the southwestern Indian Ocean, where it supports commercial fisheries. To investigate population structure and the physical processes that may have influenced female gene flow in this species, a portion of the mitochondrial DNA (mtDNA) control region (547 base pairs) was sequenced for 285 lobsters from the southeastern coast of Africa (6 sites) and 49 lobsters from Walters Shoals, a submerged seamount on the Madagascar Ridge. Lobsters from these 2 areas shared no haplotypes and differed by at least 27 mutational steps. An analysis of molecular variance showed significant genetic partitioning, and pairwise comparisons suggested that lobsters from Walters Shoals are distinct from those of other sampling areas. There was shallow genetic partitioning between 4 southern sites (South Africa) and 2 northern sites (Mozambique), suggesting 2 Management Units along the African coast. A mismatch distribution and Fu's F-test indicated fairly recent demographic changes within populations, consistent with that found in the sister species P. gilchristi. Female gene flow along the African coast may be propagated by larval dispersal in the Mozambique and Agulhas Currents and countercurrent migrations by benthic juveniles along the shelf, but the mtDNA data strongly suggest that larvae at Walters Shoals have been, or are currently still retained by other oceanographic processes. The magnitude of mtDNA divergence among lobsters from the southeastern coast of Africa and those at Walters Shoals, together with the absence of any shared haplotypes between these regions strongly suggest that these 2 taxa might in fact represent distinct species.