Scales matter: regional environment factors affect α diversity but local factors affect β diversity of macroinvertebrates in Thousand Islands Lake catchment area

A more profound comprehension of various facets of biodiversity is essential for advancing sustainable governance of biodiversity and its associated ecosystem services. In this study, we delved into the composition of beta diversity within macroinvertebrates communities in the Thousand Islands Lake catchment area. Subsequently, we investigated the factors influencing the diverse facets of macroinvertebrates alpha and beta diversity, and ultimately employed structural equation modeling to analyze the pathways through which both regional environmental factors, like climate and land use, and local environmental variables collectively impact distinct facets of alpha and beta diversity within the ecosystem. Our results showed that (i) taxonomic and phylogenetic beta diversities were primarily determined by turnover, while functional beta diversity is predominantly determined by nestedness; (ii) alpha and beta diversity are primarily influenced by spatial variables, with local environment and climate ranking the second, and land use explaining the lowest proportion according to the results of variance partitioning; (iii) alpha diversity is mainly affected by regional variables, especially climatic factors (precipitation) while beta diversity is more affected by local variables, especially hydrological factors (depth) revealed by the structural equation modeling. These results offer compelling evidence that biodiversity composition, ecological drivers, and the specific pathways of influence vary across different scales. Future studies of macroinvertebrates could focus on different facets of alpha and beta diversity as well as consider the effects of environment variables at different scales, which would provide new insights into potential patterns of community associations.