An inverse latitudinal biodiversity pattern in asellote isopods (Crustacea, Peracarida) from the Southwest Atlantic between 35° and 56°S

Abstract

A distinct trend of decreasing biodiversity from the tropics to the poles is well-known for terrestrial organisms. This pattern, however, is less clear in marine systems. In the present study, an inverse latitudinal biodiversity pattern is reported for the asellote isopods from Argentina. Species richness is shown to be about six times higher in the Beagle Channel and southern Patagonia, i.e., south of 47°S, than north of this latitude. This high species richness of Asellota south of 47°S seems to be related with the predominance of gravelly bottoms in the southern Patagonian shelf and also with the tectonic history of the southern tip of South America. Inverse latitudinal gradients had been reported previously for echinoderms, bryozoans, sponges, amphipods and macroalgae from the southern Southwest Atlantic. Based on unpublished new records and information gathered from the literature, a database summarizing the distribution ranges of the Asellota along the coast of Argentina was compiled. A total of 108 species was recorded and the distribution records of this fauna were increased by 36.15 % (260 and 354 before and after our surveys, respectively).