Linking Anthropogenic Drivers to Fish Functional Diversity: Implications for Sustainable Fishery Management in Yunnan Highland Lakes

The functional diversity of fish species contributes to the maintenance of ecosystem health and resilience to environmental differences. However, studies addressing the relationship between fish species diversity and functional diversity, in addition to their respective drivers, remain scarce. We investigated how nutrient levels affect the functional diversity of fish communities in subtropical highland lakes. By surveying lakes across a trophic gradient and analyzing fish functional traits alongside environmental data, we identified key drivers shaping diversity patterns. The non-metric multidimensional scaling (NMDS) analysis showed that functional diversity outperformed traditional taxonomic metrics in discriminating lake trophic states, thereby revealing clearer patterns of community differentiation along nutrient gradients. Overall, fish species diversity showed a positive association with functional richness; however, this relationship weakened markedly in low diversity systems such as Haixihai Lake, indicating reduced functional redundancy under species poor conditions. Moreover, dissolved oxygen, pH, and land use intensity emerged as the primary environmental drivers structuring functional diversity across lakes with contrasting trophic conditions. Finally, the three lakes demonstrated distinct eutrophication response pathways ranging from functional enhancement to species suppression and functional homogenization, underscoring the dependent context nature of nutrient impacts on freshwater fish communities. Furthermore, the marked heterogeneity among lakes is shaped by watershed dependent environmental drivers. This finding underscores that functional diversity provides a powerful framework for diagnosing ecosystem responses and informing lake specific management strategies.