Local, spatial and land use variables, rather than forest cover, drive Odonata (Insecta) beta diversity in tropical streams

Abstract Changes in land use can lead to substantial reductions in forest cover, stream environmental quality, and biodiversity. Understanding how the conversion of natural environments into different land-use types affects species replacement and richness differences, the main components of beta diversity, is therefore essential for identifying the processes structuring biological communities under intense anthropogenic pressure. Here, we evaluated the effects of land-use change, forest cover, local environmental variables, and spatial structure on the taxonomic beta diversity of adult Odonata and tested whether beta diversity components differed among land-use categories (forest, cocoa, and pasture). The study was conducted in 50 streams in the eastern Amazon distributed across forested, cocoa, and pasture landscapes. Our results showed that species replacement was identified as the most important component of total beta diversity. The spatial structure and local environmental variables, particularly stream width, were the main determinants of total beta diversity, with greater stream width associated with greater variation in species composition. Large- and medium-scale spatial structures also played a key role in explaining total beta diversity, with distinct responses among the suborders. The land uses influenced only the composition of Odonata assemblages, primarily promoting species replacement. In contrast, forest cover did not significantly affect total beta diversity or its components. Despite the absence of direct effects of forest cover on beta diversity, maintaining forest cover around streams is crucial. This practice enhances habitat quality and supports species that depend on forest-associated environmental conditions.