| Summary: | The Amazon rainforest harbours -10% of the world's birds, and more than 400 species are regularly recorded at single sites. Understanding the processes behind the generation and maintenance of biodiversity, especially on this scale, has been a central theme in the study of evolution and ecology since Darwin. Amazonian speciation and diversification models emphasise the importance ofhiogeography, geological history, and interspecifi c interactions in generating one of the most biodivcrse biomes on earth. However, the inherent ecological traits of Amazonian taxa are rarely considered. The role of rivers in Amazonian diversification is contentious, and are-evaluation of the river barrier hypothesis in the light of species ecology is timely, as behavioural, distributional and phylogenetic data for Amazonian birds are more detailed and robust than ever before. By examining the relationship between 20 major rivers and the distribution of 739 species and their subspecies in a comparative framework, I investigate (i) the role of the Amazonian river system in shaping and driving av ian diversification; (ii) how river dynamics affect river barrier strength; and (ii i) how ecology influences clade diversification propensity. I also examine (iv) how niche space is shared and partitioned, in a case study investigating mechanisms pennilting the coexistence of two closely related species of antbird. I demonstrate that rivers act as important barriers for particular ecological groups, and are stronger baniers for subspecies than species, indicating a role in recent and ongoing intraspecific diversification; that barrier strength increases with river width; Ihal dispersal limitation is a key predictor of divers ification, with higher subspecies richness in groups with poor dispersal; and that species coexistence is mediated by high levels of niche overlap. Taken together, these studies suggest that species ecology, dispersal limitation and river barriers interact to playa major role in structuring, generating and maintaining Amazonian avian biodiversity.
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