Headwater captures and the phylogenetic structure of freshwater fish assemblages: a case study in central Brazil

Aim: The astonishing diversity of Neotropical fishes results from historical and ecological processes intrinsically related to the geomorphological evolution of this region. Headwater captures are important biogeographical processes that promote dispersal or isolation of fish populations between watersheds. We investigate the effects of headwater captures on the phylogenetic structure of stream fish assemblages among watersheds in the Brazilian Shield highlands. Location: Headwaters of Tocantins, Paraná and São Francisco watersheds, Brazilian Shield, Neotropical region. Methods: Based on the phylogenetic relationships of 70 native fish species, we quantified the phylogenetic diversity of each basin, as well as species richness and the phylogenetic beta diversity between basins. Results: The Upper Paraná basin showed higher richness and phylogenetic diversity, indicating phylogenetically distant species composition. The number of shared species and phylogenetic beta diversity values were not different from the null expectation, indicating recent exchange of species between the basins. Main conclusions: Our results suggest that the fish assemblage of the Upper Paraná basin is older and many species colonized recently the neighbouring Upper Tocantins and São Francisco basins, highlighting the impact of headwater captures on the community assembly of Neotropical fishes.