Relationships between taxonomic and functional components of diversity: implications for conservation of tropical freshwater fishes

Summary Understanding the relationships between different components of diversity is needed to improve conservation strategies for freshwater habitats. Here, we studied relationships between taxonomic and functional components of fish assemblages in 27 headwater and 22 main stem habitats of tropical streams in Central Brazil. Using quantile regression analysis, we evaluated relationships between (i) taxonomic richness (S) and functional richness (FRic); (ii) taxonomic diversity (Δ+) and functional diversity (MPD) and (iii) and taxonomic richness and functional diversity. Taxonomic richness and diversity (S and Δ+) were correlated with functional richness and diversity (FRic and MPD) in headwaters and main stems. However, relationships between taxonomic and functional components differed across habitat types within a catchment. Relationships between S and FRic and Δ+ and MPD were stronger than those between S and MPD. Combined, these findings imply that caution is advised when using one diversity component as a surrogate for another diversity component in studies directed towards the conservation of fishes in tropical headwaters and main stems. Moreover, conservation and management strategies must take account of habitat‐specific relationships of the diversity components of fish assemblages when implementing management programmes.