Unveiling hidden species’ diversity within Southern Ocean Iphimediidae (Crustacea: Amphipoda) through DNA and 3D-geometric morphometrics, with the description of 10 new species

abstract The Antarctic shelf benthos is threatened by climate-related environmental changes and anthropogenic stressors. A baseline knowledge of biodiversity and species’ distribution ranges is essential for effective monitoring and conservation. Here, we integrate DNA-based species’ delimitation methods with morphological analyses to explore species’ diversity within Antarctic Iphimediidae. Our results reveal that 10 nominal species are complexes of multiple species, most of which can be distinguished by small but consistent morphological differences. We formally describe 10 of these new species: Stegopanoploea brevidentata sp. nov., Maxilliphimedia acutilobata sp. nov., Maxilliphimedia oliveri sp. nov., Echiniphimedia spinosior sp. nov., Echiniphimedia maxima sp. nov., Iphimediella longidentata sp. nov., Iphimediella brachyodonta sp. nov., Iphimediella longilobata sp. nov., Labriphimedia adeliae sp. nov., and Labriphimedia anneninae sp. nov.. Most previously recorded circum-Antarctic iphimediid species are found to consist of regionally distributed species. Furthermore, we apply 3D-geometric morphometrics on the Gnathiphimedia sexdentata complex to investigate whether ‘cryptic’ species can be differentiated by variation in continuous morphological traits. This method provides additional diagnostic characters for the morphological identification of two G. sexdentata clades. This integrative taxonomy study increases the number of nominal Antarctic iphimediid species from 39 to 49, with 14 additional putative species requiring further study for formal description.