Diversification of neotropical freshwater fishes

With more than 5,000 species, South America harbours the most taxonomically diverse fauna of continental freshwater fishes in the world. However, understanding of how major geological events over millions of years have contributed to diversity patterns in the region is poorly understood.

In this study, researchers used GBIF and other sources to compile an occurrence dataset covering 95 per cent of all the freshwater fish species described for South America, after carefully filtering, validating and revising the results. In addition, they employed a new, comprehensive molecular phylogeny based on DNA sequences from three decades of ichthyological studies, which represents 99 per cent of described genera.

By integrating occurrence and phylogenetic data, the researchers were able to estimate ancestral ranges, dispersal events and phylogenetic endemism at the subbasin level, tracking the influence of hydrogeographic events on evolutionary processes over 100 million years. The study identified five significant shifts in diversification rates, each associated with major landscape evolution events occurring during the Paleogene and Miocene (between 30 and seven million years ago).

In Western Amazonia, the high rates of diversification and extensive biotic exchanges linked to hydrogeographic events and formation of biogeographic corridors in the past 20 million years have helped shape the region's extraordinary species richness and high phylogenetic endemism.