Hydrological connectivity shapes multiple diversity facets of snail (Mollusca: Gastropoda) assemblages in freshwater floodplain wetlands

Hydrological connectivity is crucial for supporting aquatic biodiversity and serving ecosystem function in river floodplain wetlands. Although the effects of longitudinal connectivity in the composition of snail (Mollusca: Gastropoda) assemblages is well understood, the effects of lateral connectivity are less evaluated. Here, we evaluated the effects of lateral and longitudinal connectivity on multiple facets of alpha and beta diversity (i.e., taxonomic, functional, and phylogenetic) of freshwater snails in 38 floodplain wetlands in the Da Xing'an Mountains of Northeast China. A total of 9,784 snails subjected to 5 orders, 14 families, 24 genera, and 42 species were collected. Overall, the snail alpha diversity was higher in the nearly isolated wetlands and downstream areas. Multivariate analyses revealed that the taxonomic, functional, and phylogenetic structures of snail assemblages in floodplain wetlands differed significantly across the lateral and longitudinal gradients. Waterscape and climate variables appeared to equivalently explain a large proportion of variations in the taxonomic, functional, and phylogenetic structures of snail assemblages. Lateral connectivity and river order were paramount variables that explain the greatest variation in taxonomic, functional, and phylogenetic structures of the snail assemblages. Our study suggests that hydrological connectivity is a key factor controlling the multiple facets of snail diversity in floodplains. Attention should be paid to the effects of changing climate and waterscape on the multi-faceted diversity of snail assemblages. Due to the extant patterns in assemblage structures, floodplain restoration and management should consider the full spectrum of longitudinal and laterally connectedness to maximize aquatic biodiversity.