Different responses of taxonomic and functional structures of stream macroinvertebrate communities to local stressors and regional factors in a subtropical biodiversity hotspot

Abstract

Examining the relative contribution of local environmental stressors and regional factors in structuring biological communities is essential for biodiversity conservation and environmental assessment, yet their relative roles for different community characterizations remain elusive. Here, we examined the responses of taxonomic and functional structures of stream macroinvertebrate communities to local and regional factors across a human-induced environmental gradient in the Han River Basin, one subtropical biodiversity hotspot in China. Our objectives were: 1) to examine the responses of traditional taxonomic measures and functional traits to anthropogenic disturbances; 2) to compare the relative importance of environmental versus spatial variables and catchment-scale versus reach-scale variables for the two community characterizations. We found that both species and trait compositions performed well in differentiating anthropogenic disturbances, indicating that both taxonomic and functional structures of macroinvertebrate communities were strongly altered by human activities. Particularly, some traits related to life history (e.g., voltinism), resilience and resistance (e.g., adult flying ability) are well suited for predicting changes of communities towards anthropogenic disturbances owing to their mechanistic relationship with environmental gradients. We found that environmental variables played more important roles than spatial effects in structuring both taxonomic and functional facets of macroinvertebrate communities. Environmental filtering was more important in determining functional than taxonomic structure, and the opposite was true for spatial effects. In terms of environmental variables, catchment land-uses played the primary role in determining taxonomic composition, whereas reach-scale variables related to local habitat heterogeneity were more influential for functional structure. Our study highlights the importance of employing metacommunity perspectives and different community characterizations in both theoretical and applied research. For stream bioassessment and management, we argue that the combination of taxonomic and functional characterizations of community should be implemented, as different facets of biological communities responded to different types of anthropogenic disturbances.