The role of the environment and connectivity on multiple facets of local fish diversity in tropical headwater streams

Abstract

1. The identification of multiple facets of biodiversity (e.g., phylogenetic and func-tional) can help to understand how evolutionary and ecological mechanisms shapethe assembly of biological communities.2. Here, we employed multiple regressions and variance partitions to investigate theeffects of environmental conditions, connectivity and space on aspects of thefunctional and phylogenetic facets of fish fauna in tropical headwater streams ofthe Xingu River basin, in Eastern Amazonia.3. We found that the functional and phylogenetic diversities of fish communities arerelated to local environmental conditions and stream connectivity in the drainagenetwork, with marked differences occurring between the rainy and dry periods.Furthermore, we discovered that functional uniqueness was influenced mainly byenvironmental factors, whereas phylogenetic uniqueness had a more complex re-lationship with the influence of local environmental factors and connectivity.4. Our findings indicate that the fish assemblages of small headwater streams of theXingu River basin share a close phylogenetic history. This is probably because ofthe climatic and environmental stability experienced by Amazonian ichthyofaunaover evolutionary time.5. Our findings emphasise the role of niche-based processes in shaping the uniquefunctional composition of fish assemblages in headwater streams, and highlightthe importance of environmental heterogeneity in maintaining the ecological in-tegrity of these freshwater ecosystems