| Summary: | Recent molecular analyses revealed that several so-called “circum-Antarctic” benthic crustacean species appeared to be complexes of cryptic species with restricted distributions. In the Southern Ocean, the superfamily Lysianassoidea is one of the most important amphipod groups, both in terms of species number and abundance. In this study we used a DNA barcoding approach based on mitochondrial cytochrome oxidase I gene sequences in order to detect possible cryptic diversity and to test the circumpolarity of some lysianassoid species. This gene fragment performed as a powerful barcoding marker, showing a clear barcoding gap between intra- and interspecific divergences of well-identified species. In several species, a genetic homogeneity was found even among specimens from remote sampling sites which indicates a possible circum-Antarctic and eurybathic distribution. In other species, genetically divergent lineages and possible cryptic taxa were revealed. Results might be explained by the different dispersal and gene flow capability of these amphipods as well as by the generally insufficient knowledge on the biodiversity of the Antarctic fauna related to species identification. 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 assessment studies are of particular importance since they may serve as a basis for monitoring and conservational efforts. In this context, DNA barcoding can thus be a useful and cost-effective tool.
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