Using functional traits of chironomids to determine habitat changes in subtropical wetlands

Ecosystem functions in wetlands are increasingly degrading under the multiple stresses of climate change and human disturbances. Traditional wetland bioassessment is usually based on taxonomic approaches but this approach has limitations. To explore the effectiveness of functional traits in response to environmental changes, we compared the traditional taxonomic composition of chironomid communities with a trait-based approach in a subtropical subalpine wetland (Central China) spanning a wide habitat gradient from dry peatland to inundated peatland pools. The results revealed that 57 % of functional trait groups but only 38 % of taxonomic groups examined were significantly different between diverse peatland habitats. Sphagnum moss hummocks were generally inhabited by larvae of collector-gatherers, small body-sized individuals and sprawlers, while peatland pools supported a high abundance of shredders, large body-sized larvae and burrowers. Ecotones had more niche opportunities and hence possessed high taxonomic and functional diversity. Ordination analyses indicated that three similar environmental variables (loss-on-ignition (LOI), depth to water table (DWT) and K+) were the most powerful explanations of the chironomid variability in both taxonomic and functional trait compositions. LOI and DWT interacted strongly and were the dominant controls on both taxonomic and trait communities. Our research demonstrated that functional trait groups of chironomids are more robust and sensitive than taxonomybased approaches to habitat changes, and therefore could be an alternative approach for the bioassessment of aquatic ecosystem functioning and palaeo-studies in wetlands.