Metacommunity organisation of Amazonian stream fish assemblages: The importance of spatial and environmental factors

Metacommunity theory seeks to explain how local and regional processes contribute to the organisation of biological communities. Recent conceptual frameworks of this theory indicate that the dynamics of populations and communities are jointly established by dispersal, species responses to environmental conditions and biotic interactions dependent on species density. Here, we use hierarchical joint species distribution modelling to verify the effects of environmental factors (at multiple spatial scales), drainage network configuration, spatial autocorrelation and interspecific interactions on the structure of fish assemblages in terra-firme streams in the Eastern Brazilian Amazon. Thirty streams were sampled in two field surveys, and 89 species were collected in total. Our results confirm the effects of limited dispersal, environmental conditions (at multiple scales) and the configuration of the drainage network on the dynamics of these assemblages. Furthermore, our results suggest that interspecific interactions are less relevant for the structuring of fish metacommunities in small Amazonian headwater streams. Abiotic factors like drainage networks and environmental heterogeneity were better predictors of species distributions than co-occurrence patterns with potential competitors or predators.