Elevational patterns of trait composition and functional diversity of stream macroinvertebrates in the Hengduan Mountains region, Southwest China

Abstract

Stream ecosystems in high-mountain regions are susceptible to rapid environmental change, including warming and increased human activities. Understanding elevational patterns of stream communities and underlying drivers can facilitate the development of efficient conservation and management strategies to mitigate the impacts of these changes. Our study investigated elevational patterns of macroinvertebrate trait composition and functional diversity in six streams in the Hengduan Mountains region, Southwest China, which was recognized as one of the global biodiversity hotspots. We were particularly interested in untangling the effects of watershed human disturbance and instream physicochemical factors on elevational patterns of stream macroinvertebrates. Our results showed clear elevational patterns in both trait composition and functional diversity of macroinvertebrate communities. For trait composition, the results indicated that macroinvertebrate traits associated with mobility, habit, and feeding mode exhibited clear elevational patterns. For functional diversity, functional richness showed a positive correlation with elevation, whereas functional divergence had the opposite trend. No significant elevational pattern was detected in functional evenness and RaoQ. Further analyses found that weak human disturbance was the most important driver shaping trait composition and functional diversity of macroinvertebrates. Meanwhile, instream water temperature, primary productivity, and flow velocity also played considerable roles. Our study emphasizes the influence of watershed human disturbance on elevational patterns of macroinvertebrates in high-mountain streams. It also highlights the potential of trait composition and function diversity of macroinvertebrates as indicators for monitoring the ecological status of high-mountain streams.