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There are relatively few studies examining the latitudinal distribution of polar, subantarctic and temperate faunas on the bathyal seafloor across the Southern Ocean. Here, we investigate the relationship between the subantarctic Macquarie Ridge and adjacent regions of Antarctica (including the Ross Sea) and temperate Australia and New Zealand at depths of 200-2,500 m. We study the fauna at two levels of classification (1) morpho-species (MSPs) accepted by taxonomists and (2) evolutionary significant units defined as reciprocally monophyletic clades derived from phylogenies of mitochondrial DNA. The ophiuroid fauna on the Macquarie Ridge has a predominantly temperate origin, with far more MSPs shared with south-eastern Australia (78 % of species) and southern New Zealand (83 %) than neighbouring Antarctic regions (33 %). However, this asymmetry also reflects the relative species richness of these regions. Many species that are shared between Antarctica and the Macquarie Ridge have diverged into distinct mtDNA lineages indicative of a recent barrier to gene flow. [ABSTRACT FROM AUTHOR]

The shelled pteropod (sea butterfly) Limacina helicina is currently recognised as a species complex comprising two subspecies and at least five ''forma''. However, at the species level it is considered to be bipolar, occurring in both the Arctic and Antarctic oceans. Due to its aragonite shell and polar distribution L. helicina is particularly vulnerable to ocean acidification. As a key indicator of the acidification process, and a major component of polar ecosystems, L. helicina has become a focus for acidification research. New observations that taxonomic groups may respond quite differently to acidification prompted us to reassess the taxonomic status of this important species. We found a 33.56% (60.09) difference in cytochrome c oxidase subunit I (COI) gene sequences between L. helicina collected from the Arctic and Antarctic oceans. This degree of separation is sufficient for ordinal level taxonomic separation in other organisms and provides strong evidence for the Arctic and Antarctic populations of L. helicina differing at least at the species level. Recent research has highlighted substantial physiological differences between the poles for another supposedly bipolar pteropod species, Clione limacina. Given the large genetic divergence between Arctic and Antarctic L. helicina populations shown here, similarly large physiological differences may exist between the poles for the L. helicina species group. Therefore, in addition to indicating that L. helicina is in fact not bipolar, our study demonstrates the need for acidification research to take into account the possibility that the L. helicina species group may not respond in the same way to ocean acidification in Arctic and Antarctic ecosystems. [ABSTRACT FROM AUTHOR]

Abstract: Three hundred and fifty specimens of the endemic Southern Ocean octopus genus Pareledone, were sequenced for the barcoding gene COI. Geographic coverage comprised the South Shetland Islands, the Ross Sea, Adélie Land, George V Land, the Weddell Sea, under the site of the former Larsen B ice shelf, Prydz Bay, the South Orkney Islands and the Amundsen Sea. The greatest number of specimens was captured at the three first-mentioned localities. At least 11 species were represented in the samples and the analyses revealed cryptic species. Six species were found to have extended distributions. Circumpolarity is supported for at least one species. Evidence is presented for a barrier to gene flow to the west of the Antarctic Peninsula, with haplotypes of P. aequipapillae becoming progressively more diverse in a clockwise direction from the South Shetland Islands to the Amundsen Sea. This pattern is akin to that seen in ring species, although we suggest that comparatively warm bottom water acts as a physical barrier preventing completion of the ring. [Copyright &y& Elsevier]