CONICET | Buscador de Institutos y Recursos Humanos

The ?East Pacific Barrier? has been recognized as the World´s largest marine biogeographic barrier. Munida gregaria is the only species of its family with transpacific populations; however, it still remains to be elucidated whether these two distantly located populations belong to the same species. In this study we investigated the genetic cohesion of M. gregaria across the East Pacific Barrier by analyzing mitochondrial markers. COI and ND1 genes were sequenced for individuals from eight localitiesdifferent areas, i.e. one in the South East Pacific, two in the South southern tip of South America, East Pacific/the South West Atlantic, four in the South West Atlantic, and one in the South West Pacific. A median-joining network, AMOVA, pairwise FSTs, genetic diversity statistics and neutrality tests were computed. Our results, i.e. absence of different haplogroups on both sides of the East Pacific Barrier and existence of shared haplotypes, showed that populations on both sides of this barrier belong to the same species. At a population genetic level, our results suggest that individuals from both regions have been connected, since although some differentiation was found between the southern tip of South America and the South West Pacific, the South East Pacific and South West Atlantic showed no signs of differentiation from the South West Pacific. The analyses performed showed no genetic differentiation between transpacific populations of M. gregaria suggesting that there has been enough gene flow to maintain species cohesion. In addition, our results provided evidence of a spatial expansion in southern South America during the Middle Pleistocene. The role of Pleistocene glaciations and the Antarctic Circumpolar Current in shaping the distribution of sub-Aantarctic marine invertebrates is discussed. Overall, Munida gregaria constitutes a truly transpacific species.