Unraveling the role of environmental factors and dispersal capacity in a metacommunity of Amazonian stream fishes

Separating species in terms of dispersal capacity can be useful to understand how local and regional factors affect the distribution of organisms in metacommunities. In this study, we sought to unravel how the characteristics of local habitats and spatial distances structure fish communities in Amazonian streams. We hypothesized that fishes classified with high dispersal capacity are mainly structured by mass effects and respond to environmental and spatial variables in the same proportion, while fishes classified with low dispersal capacity are mainly structured by species sorting, responding mainly to local environmental variables. We collected fish from 36 well-preserved streams in the Capim river basin in northern Brazil during the dry season. In general, the community composition was structured by characteristics of the local habitat. Spatial variables influenced each group at different intensities, agreeing with the models of species sorting and mass effects and corroborating our hypotheses. Thus, our findings suggest that the dispersal mode affects how metacommunities are structured. The differences in the patterns observed between the groups compared can help in the management and conservation of species, such as those with greater environmental requirements and more susceptible to habitat changes. We emphasize the need to maintain habitat integrity and connectivity in headwater streams to conserve species in their habitats.