The relative role of rivers, environmental heterogeneity and species traits in driving compositional changes in Southeastern Amazonian bird assemblages

Amazonian rivers have been proposed to act as geographic barriers to species dispersal, either driving allopatric speciation or defining current distribution limits. The strength of the barrier varies according to the species ecological characteristics and the river physical properties. Environmental heterogeneity may also drive compositional changes, but have hardly been assessed in Amazonia. Aiming to understand the contributions of riverine barriers and environmental heterogeneity in shaping compositional changes in Amazonian forest bird assemblages, we focus on the Tapajós River. We investigate how spatial variation in species composition is related to physical barriers (Tapajós and Jamanxim rivers), ecological characteristics of the species (distinct guilds) and environmental heterogeneity (canopy reflectance, soils and elevation). We sampled birds through point counts and mist nets on both banks of both the Tapajós and Jamanxim rivers. To test for relationships between bird compos...