Biological invasions are a major driver of biodiversity loss in freshwater ecosystems, yet the mechanisms determining community resistance to invasion remain highly debated. In particular, the long-standing invasion paradox has generated conflicting evidence regarding the role of native biodiversity in resisting invasions.

Recently, researchers from the Institute of Hydrobiology (IHB), Chinese Academy of Sciences, together with collaborators from Hunan University of Science and Technology, the University of León (Spain), Zhejiang Freshwater Fisheries Research Institute, and other institutions, identified a global mechanism underlying biotic resistance to freshwater fish invasions. The study was published in Global Change Biology.

Using freshwater fish assemblages from 2622 river basins worldwide, the researchers quantified niche, functional, and phylogenetic differentiation within native fish communities and evaluated their effects on non-native fish occurrence and richness. The analyses incorporated human pressure, basin area, latitude, and other environmental factors.

The results showed that native niche differentiation was the strongest predictor of invasion resistance. Higher niche differentiation was consistently associated with lower occurrence and richness of non-native fishes, suggesting that more complete resource use and stronger competitive interactions among native species enhance resistance to invasion. This pattern was remarkably consistent across the globe and among all six major freshwater biogeographic realms.

The study also found that human activities strongly promote invasions, while invasion intensity peaks at intermediate latitudes.

Overall, the findings highlight native community niche structure as a key determinant of biotic resistance, providing a unified explanation for the invasion paradox and offering new insights for freshwater invasion management under global change.

(Editor: MA Yun)