Domestic and exotic freshwater fish communities of different water systems under anthropogenic pressures: Diversity...

Human activity threatens freshwater fish biodiversity, with non-native species driving functional homogenization and biodiversity loss. This highlights the critical need to investigate the diversity, environmental drivers and ecological interactions between native and non-native communities. This study investigates domestic and exotic fish diversity using environmental DNA (eDNA) sampling across 112 rivers, lakes, and reservoirs in Jiangsu Province, China. A joint species distribution model (JSDM) is applied to identify correlated environmental variables and biotic associations shaping fish community. We also quantify the impact of land use on water quality and propose a trait-based framework to predict potential vulnerable functional space. Our findings suggest that fish diversity patterns differ in lotic and lentic systems. Nutrients (total phosphorus, ammonia nitrogen) and pollutants (fluoride, five-day biochemical oxygen demand (BOD₅)) are key factors affecting regional fish community, with domestic fish being more sensitive to pollutants than exotic species. Exotic species with functional traits similar to those of the domestic community at the community level but distinct at the individual level tend to establish through preadaptation, further promoting the functional homogenization of ecosystems. A framework for predicting vulnerable functional space is proposed based on trait-based analysis, which underscores the importance of identifying functional traits and community structure. In conclusion, fish communities in Jiangsu are shaped by abiotic factors filtering specific functional traits and biotic relationships driving ecological interactions. Our study provides insights into conserving aquatic ecosystems and managing non-native species.