The decomposition of beta diversity reveals the difference between crustacean and rotifer communities in response to environmental change in tropical reservoirs

Crustaceans and rotifers are key components of freshwater ecosystems, exhibiting distinct life-history strategies and functional traits. However, these two groups are often integrated into a single assemblage in analysis of zooplankton communities, potentially obscuring the mechanisms underlying community variation. As a key measure of community variation, beta diversity (β-diversity) and its decomposition provide critical insights into the processes shaping community structure. We compared β-diversity patterns of crustaceans and rotifers across 21 tropical reservoirs within a large river basin, applying two complementary decomposition frameworks. Crustacean β-diversity showed higher nestedness and lower turnover components than that of rotifers. Both Mantel tests and Generalized Dissimilarity Modeling (GDM) revealed that crustacean community variation was jointly influenced by environmental filtering—primarily total phosphorus concentration and rotifer abundance—and weak dispersal limitation associated with spatial distance. In contrast, rotifer communities were mainly shaped by environmental filtering. Local Contribution to Beta Diversity (LCBD) further indicated spatial asynchrony between crustaceans and rotifers. Structural Equation Modeling (SEM) confirmed differences in food resource preferences between the two groups: crustaceans responded strongly to cryptophyte biomass, whereas rotifers were more associated with cyanobacterial biomass. Our findings suggest that contrasting functional traits and feeding strategies lead to distinct β-diversity patterns and environmental responses between crustaceans and rotifers. These results underscore the importance of analyzing these groups separately to improve ecological monitoring, biodiversity assessment, and the understanding of community assembly mechanisms. • The study reveals significant differences in β-diversity composition between crustaceans and rotifers. • Environmental filtering and dispersal limitation jointly drive variation in crustacean communities, whereas rotifer communities are mainly shaped by environmental filtering. • Differences in food resource preferences may lead to the spatial asynchrony of the LCBDs between crustaceans and rotifers. • These findings highlight the crustaceans and rotifers must be analyzed separately to ensure accurate freshwater ecosystem assessments.