Seasonal variation and driving factors of beta diversity of macroinvertebrate assemblages in subtropical Chinese high-mountain streams

High-mountain stream ecosystems are recognized as ideal arenas for natural experiments and for ecological monitoring and assessment research, owing to their sensitivity to climate gradients and human-mediated disturbances. In this study, we chose a subtropical mountainous stream system in southwestern China, to explore the spatiotemporal patterns and driving factors of taxonomic, phylogenetic, and functional beta diversity of macroinvertebrate assemblages. We found that taxonomic beta diversity was highest (on average, 0.577 in spring and 0.645 in autumn) across seasons, followed by phylogenetic (0.491 and 0.545) and functional (0.350 and 0.383) beta diversity, with the replacement component predominantly (57%–73%) contributing to all three facets of diversity. The taxonomic local contributions to beta diversity (LCBD) values were roughly equivalent among different sites in both spring and autumn, whereas phylogenetic LCBD (PLCBD) and functional LCBD (XLCBD) indices varied from site to site. Therefore, we recommend prioritizing site conservation based on LCBD, PLCBD, and XLCBD values to optimize biodiversity conservation strategies. The three-facets of dissimilarities were all somewhat higher in autumn than spring, possibly due to recolonization events in the metacommunity after the summer flood. Variation partitioning analysis indicated that environmental factors were more important than spatial factors in structuring all three facets of beta diversity and their components, although different sets of variables were identified as important for different diversity facets and between seasons. In summary, our study offers valuable insights into the patterns and drivers of macroinvertebrate beta diversity in high mountain streams and lays a baseline for targeted conservation strategies in these ecosystems.