Cryptic diversity down under: defining species in the subterranean amphipod genus Nedsia Barnard & Williams, 1995 (Hadzioidea: Eriopisidae) from the Pilbara, Western Australia

Amphipod crustaceans comprise a significant and enigmatic component of Australian groundwater ecosystems, particularly in the Pilbara region of Western Australia. Many amphipod species in the Pilbara, including species in the genus Nedsia Barnard & Williams, 1995, are considered short range endemics, poorly or contentiously defined by taxonomic treatments based on morphology alone and have uncertain distributions as a consequence of this taxonomy. A modern systematic revision of Nedsia is presented here, utilising both molecular and morphological analyses alongside distributional data to delineate species. We describe 13 new species of Nedsia, confirm three existing species and synonymise eight previously described species. Nedsia species are confirmed to be functionally morphologically cryptic, with COI divergences at the 5-20% level. We present comparatively reduced taxonomic descriptions for these cryptic amphipod species in an effort to provide an accelerated pathway for future taxonomic work. The research provides the basis for future environmental impact assessments involving Nedsia species and ongoing monitoring of the groundwater communities these form part of in the resource-rich Pilbara region.