Functional homogenization in aquatic ecosystems: a review and framework proposal

Functional homogenization can be defined as a simplification of functional communities or species traits over time. The purpose of this review was to summarize the existing quantitative evaluations of functional homogenization (FH) in aquatic ecosystems, as well as to propose a framework to guide future research. Few articles have quantitatively evaluated FH to date. Although FH is an expected pattern in most studies given the anthropogenic impacts of the Anthropocene era, the result depends on the same factors, like temporal and spatial scales and biological groups. Largely, fish were the most investigated, freshwater was the most evaluated ecosystem, and within these, FH patterns were frequently evidenced with relatively lower connectivity, and were usually associated with an increase in generalist non-native species. The poor link between traits and ecosystem functioning in most studies highlights the need for a better definition of functional measurements for several biological groups. We urge standardized monitoring studies and further research in marine and estuarine ecosystems. Studies on cross-taxa effects as well as a better choice of complementary traits should be encouraged. For that, we suggested a framework to serve as a guide for future studies, to better inform the management and conservation of ecosystem services.