Towards a better understanding of Southern Ocean biogeography: new evidence from benthic hydroids

Benthic hydroids are an important component of the Antarctic benthic ecosystem. They have been studied since the first Antarctic expeditions, and in recent years, there has been an important increase in biodiversity studies. In order to analyse the relationship among different areas and validate/dismiss previous biogeographical hypotheses, we have compiled all valid records of the known benthic hydroid species from the Antarctic and Sub-Antarctic regions, and used two previous scheme divisions of the Southern Ocean. In both cases, a hierarchical cluster was performed with the SIMPROF test. Our results suggest the division of the Southern Ocean into three main regions: the first corresponds to the classical Patagonian region; the second consists of the Kerguelen Archipelago, Crozet Island, Prince Edward Islands and Bouvet; the third, here referred to as the Antarctic region, is formed by South Georgia, the Scotia Arc archipelagos and High Antarctica. The results obtained also support the classical division of High Antarctica into two subregions, corresponding to West and East Antarctica. Nevertheless, the limits between both regions are still unclear, mainly because of the scarcity of data from some areas and the complete absence of information from others.