Riverscape dynamics and habitat utilization structure evolutionary diversification in a clade of Amazonian electric fishes.

Rivers have long been implicated in the processes of macroevolutionary diversification, but only recently have tools emerged to quantify habitat volume and connectivity across modern and ancient landscapes. Here we compare biodiversity patterns in a diverse clade of Amazonian electric fishes with the predictions of three alternative hypotheses of rivers as: (1) semi-permeable dispersal barriers, (2) branching drainage networks, and (3) dynamic with a reticulated history of connections; i.e., river capture. We found support for all three hypotheses, with large river corridors as partial dispersal barriers to small-river species, interfluves as barriers to large-river species, and contrasting patterns of local (alpha) diversity and species-turnover (beta diversity) in large and small rivers. River captures are faster in smaller rivers with rare but expansive mega-river capture events, facilitating dispersal of small-river clades across watersheds. These results support the role of riverine dynamics as principle agents driving continental diversification of megadiverse tropical aquatic faunas.