Biogeographic patterns of Chilean littoral fishes

In this study, we analyzed the biogeographic patterns of the Chilean littor al fish fauna, including latitudinal trends in teleost and chondrichhyan fi sh species richness, their distribution range patterns, and their level of endemism, both to the Chilean coast and the Southeastern Pacific. We determ ined the number and percentage of fish taxa within four different groups ba sed on their biogeographic affinities. This was done, both for teleost and chondrichthyan fishes, at the species, genus and family level. In order to recognise the existence of biogeographic regions, we applied cluster and or dination analyses to the distribution data, using objective bootstrapping t echniques at the three taxonomic levels used. We found that littoral fish d iversity remains fairly constant along the coast down to around 40 degrees S, declining south of this latitude. We detected two biogeographic regions along the Chilean coast, with a break between them at 40 degrees S. These r esults lend support to previously recognized biogeographic provinces or fau nistic units. These two biogeographic regions are a reflection of the mixed origin of the Chilean littoral ichthyofauna, consisting of northern warm-t emperate fishes of subtropical origin and southern cold-temperate fishes of subantarctic origin. While the percentage of fishes endemic to the Chilean coast is not high (18%), a large percentage of teleost species inhabiting Chilean littoral waters are endemic to the Southeastern Pacific (44%). Disp ersal and evolutionary history, rather that other factors, seem to explain the observed patterns of distribution of this: particular fish fauna. This study represents a necessary first step towards understanding the biogeogra phy of Southeastern Pacific marine fishes.