Convergence of trait–habitat relationships across evolutionary and biogeographically distinct assemblages would suggest key, repeated mechanisms play a role in structuring assemblages along environmental gradients. However, few studies at the assemblage level have involved analyzing quantitative data collected using standardized methods at the global scales to study such convergence. In this study, we tested the hypothesis that patterns of trait–habitat relationships converge across zoogeographic regions due to universal environmental filters acting on functional traits. The fish assemblages of forty small streams were sampled at multiple scales (microhabitat, stream reach, and region) for all teleost fishes from five distinct zoogeographic regions across the globe including: North America, South America, Central America, Asia, and Africa. Using thirty functional traits and various multivariate techniques, the convergence of traits-habitat relations were analyzed within and across all zoogeographic regions for single traits and trait groups.
Results/Conclusions
Convergence of trait–habitat relationships was found across all zoogeographic regions for some but not all traits. In addition, functional diversity increased with instream structure and variation of water velocity, which has management implications. Habitat features, such as substrate and water velocity, were shown to limit the traits found in specific habitat types across all zoogeographic regions, suggesting that these features act as universal environmental filters for these fish assemblages. However, not all trait habitat-relationships were found at each zoogeographic region. This suggests that these relationships need to be tested for each region before trait-based approaches can be useful tools for predicting fundamental assemblage patterns.