| Summary: | Repeated cycles of glaciation have had major impacts on the distribution of genetic diversity of the Antarctic marine fauna. During glacial periods, ice cover limited the amount of benthic habitat on the continental shelf. Conversely, more habitat and possibly altered seaways, were available during interglacials when the ice receded and the sea level was higher. We used microsatellites and partial sequences of the mitochondrial cytochrome oxidase c subunit 1 (MT-CO1) gene to examine genetic structure in the direct-developing, endemic Southern Ocean octopod Pareledone turqueti Joubin, 1905 sampled from a broad range of areas that circumvent the Antarctic continent. We find that, unusually for a species with poor dispersal potential, P. turqueti has a circumpolar distribution and is also found off the islands of South Georgia and Shag Rocks. The overriding pattern of spatial genetic structure can be explained by hydrographic (with ocean currents both facilitating and hindering gene flow) and bathymetric features. The Antarctic Peninsula region displays a complex population structure, consistent with its varied topographic and oceanographic influences. Genetic similarities between the Ross and Weddell Seas, however, are interpreted as a persistent historic genetic signature of connectivity during the hypothesized Pleistocene Western Antarctic Ice Sheet collapses. A calibrated molecular clock indicates two major lineages within P. turqueti, a continental lineage and a subAntarctic lineage, that diverged in the mid-Pliocene with no subsequent gene flow. Both lineages survived subsequent major glacial cycles. Our data are indicative of potential refugia around the Antarctic continent within the Ross Sea, Weddell Sea and off Adélie Land, with mean age of mtDNA diversity within these main continental lineages coinciding with Pleistocene glacial cycles. Pareledone_turqueti_microsats Pareledone_turqueti COI sequence data for Pareledone turqueti individuals from Antarctica.
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