| Summary: | By molecular analyses (using COI and 28S rRNA), we investigated for several lysianassoid species: (i) their circumpolarity, (ii) the link between the Magellan region, the Scotia Arc and the Antarctic Peninsula and (iii) the link between the Antarctic regions and the southwest Atlantic abyssal basin. In several species, a genetic homogeneity was found even among specimens from remote sampling sites indicating a circum-Antarctic and eurybathic distribution. In other species, genetically divergent lineages and possible cryptic taxa were revealed. Moreover, in some abyssal lysianassoids, identical haplotypes were found between the Antarctic Peninsula, the Weddell Sea and the Argentine abyssal basin, while high genetic divergences were detected between these regions and the Brazil abyssal basin. This can be explained by the northward movement of the Antarctic bottom water, formed in the Weddell Sea and connecting the Antarctic and Argentine abyssal basins. Based on these observations, our current view on the species richness and distribution of the Antarctic lysianassoids may have to be modified. As polar regions are more affected by climate change than others, biodiversity and phylogeographic studies are of particular importance since they may serve as a basis for monitoring and conservational efforts.
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