Causes and consequences of biotic homogenization in freshwater ecosystems

Biotic homogenization goes beyond the increase in taxonomic similarity among communities. It also involves the loss of biological differences in any organizational level (e.g., populations or communities) in terms of functional, taxonomic or genetic features. There are many ways to measure biotic homogenization, and the results depend on temporal and spatial scales, the biological group, and the richness of the communities. In freshwater ecosystems, the main investigated causes of biotic homogenization correspond to the introduction of non-native species, damming, and changes in land use. However, other natural and anthropogenic causes also increase similarity among aquatic biota, such as climatic change, changes in productivity, and flood and drought events. The consequences of biotic homogenization in freshwater ecosystems are less explored than its causes, despite its severe implications, such as lesser resistant/resilient communities, loss of ecosystem functions, and higher vulnerability to diseases. Finally, biotic homogenization is a complex process that requires attention in conservation strategies, especially because forecasts suggest that freshwater biotas will continue to become more homogeneous in the future.