CONCLUSION
Our study reveals the manner in which patterns and extent of fish homogenization and differentiation induced by low-head dams in subtropical streams in China. In this study, we found that taxonomic differentiation accompanied functional homogenization in stream fish assemblages because of the decrease in abundance of shared native species with unique functional traits. More importantly, these results showed the importance of population abundance in structuring fish faunal homogenization and differentiation at small scales, especially when the major differences among assemblages are in species abundance ranks rather than species identities. Additionally, our study proved that changes in taxonomic similarity cannot be used to predict changes in functional similarity. Considering the dynamic processes of biotic homogenization and differentiation, fish assemblages could exhibit homogenization in the future as native-invasive species continue to spread and native species become extirpated. Therefore, future studies should continue monitoring to protect existing biodiversity that aimed at mitigating the ecological effects of low-head dams.