Hydrological connectivity drives multi-trophic biodiversity and food-web structure in Yangtze River wetlands: Insights from eDNA metabarcoding

Hydrological connectivity is a fundamental regulator of the exchange of matter, energy, and organisms across aquatic and terrestrial ecosystems, especially within wetlands. Despite this critical role, its ecological effects on communities across multiple trophic levels remain insufficiently understood. In this study, we investigated the responses of biodiversity and food web structure to hydrological connectivity based on aquatic environmental DNA data encompassing fish, invertebrates, protozoa, eukaryotic algae, fungi, and bacteria from the middle reaches of the Yangtze River wetlands. Hydrological connectivity exerted limited and taxon-specific effects on α diversity, but had a strong and nonlinear influence on β diversity. Community compositional heterogeneity peaked at intermediate levels of connectivity. Patterns of community stability, quantified by the average variation degree, indicated that hydrological connectivity was the dominant driver for most taxa. Conversely, local nutrient and physicochemical conditions more strongly controlled lower trophic groups such as bacteria and fungi. Food web patterns revealed pronounced nonlinear responses to hydrological connectivity, with trophic coherence and modularity exhibiting U-shaped relationships and robustness reaching its maximum at intermediate connectivity levels. Our findings underscore the central role of hydrological connectivity in structuring both biodiversity patterns and food-web architecture across trophic levels, and highlight its importance for effective conservation and management of wetland ecosystems under changing hydrological conditions.