Functional Diversity Indices and Aquatic Macrophyte Community Assembly: Case Study of Dnipro–Orilsky Nature Reserve, Ukraine

Background: Functional diversity of aquatic macrophytes can provide mechanistic insight into community assembly beyond taxonomic diversity metrics. Aims: We tested whether functional diversity indices can help infer the dominant processes shaping macrophyte communities along hydromorphological and physicochemical gradients, and whether these signals remain interpretable after accounting for species richness. Methods: We surveyed aquatic macrophytes in the Dnipro–Orilsky Nature Reserve (Ukraine) during four field campaigns in 2024 (453 sampling sites), measured key environmental characteristics, and calculated functional diversity indices from plant trait data. Results: The indices showed distinct responses consistent with environmental filtering, dispersal limitation related to reduced hydrological connectivity, and biotic interactions. Anthropogenic degradation was associated with functional simplification and shifts toward opportunistic trait syndromes. Conclusions: A complementary set of functional diversity indices can distinguish major community assembly mechanisms in macrophyte assemblages and supports more robust assessment of ecosystem condition under combined natural and anthropogenic pressures.