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Understanding how environmental change and species introductions shape functional diversity is essential for conserving freshwater biodiversity. This study examines these drivers in the upper Yuan-Red River Basin over three decades (1990-2020). Using morphological traits from fish specimens, we applied generalized least squares models, hypervolume analysis, and variation partitioning to assess trait variation, functional space reorganization, and contributions of native versus non-native species. Functional space overlap between periods was only 20.6% for natives, while non-natives expanded rapidly, increasing overlap with natives from minimal to 40% by the 2020s. Locomotion traits associated with precipitation and non-native richness; feeding and habitat traits with dams, non-native richness, and water quality. Diversity indices remained stable and climatically driven, despite underlying trait restructuring. Conservation should prioritize maintaining natural flow regimes.
Huang et al. (Fri,) studied this question.