Environmental Filtering Maintains Macroinvertebrate Diversity in the Upper Jinsha River

Elucidating the mechanisms that influence the assembly and maintenance of communities is a crucial objective in ecological research. However, the mechanisms underlying the maintenance of macroinvertebrate community structure in large rivers on the Tibetan Plateau are still not well understood. To this end, we systematically investigated the spatial distribution characteristics of community diversity and its maintenance mechanisms, focusing on the upper Jinsha River as our study region. During the period from November to December 2022, we collected a total of 126 macroinvertebrate species, representing 5 phyla, 7 classes, 14 orders, 53 families, and 96 genera. Our findings revealed notable variations in species composition among macroinvertebrate communities inhabiting the mainstem and its tributaries. Macroinvertebrate densities, biomass, and species richness were significantly higher in tributaries compared to the mainstem. Additionally, there were significant differences in the Margalef richness index, Pielou evenness index, Shannon diversity index, functional richness, and functional divergence when comparing the mainstem and tributary streams, whereas phylogenetic diversity showed no significant variations. Redundancy analysis demonstrated that the structure of macroinvertebrate communities was notably influenced by a combination of environmental and spatial variables, although the key factors varied among different water bodies. Furthermore, variance partitioning analysis indicated that deterministic processes predominantly shaped macroinvertebrate community assembly, while stochastic processes had a secondary influence. These findings enhance our understanding of macroinvertebrate community dynamics in high-altitude river systems and provide a scientific basis for the conservation of riverine ecosystems and aquatic biodiversity in the upper Jinsha River.