Is Munida gregaria (Crustacea: Decapoda: Munididae) a truly transpacific species?

Abstract

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. Cytochrome oxidase subunit I and NADH dehydrogenase subunit 1 genes were sequenced for individuals from different areas, i.e., the southeast Pacific, the southern tip of South America, the southwest Atlantic, and the southwest Pacific. A median-joining network, pairwise F STs, genetic diversity statistics, and neutrality tests were computed. Our results, i.e., the 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 southwest Pacific, the southeast Pacific and southwest Atlantic showed no signs of differentiation from the southwest Pacific. In addition, our results provided evidence of a population expansion in southern South America during the Pleistocene. The role of Pleistocene glaciations and the Antarctic Circumpolar Current in shaping the distribution of sub-Antarctic marine invertebrates is discussed.