Functional structure and beta diversity of butterfly communities in a Chinese biodiversity hotspot.

Due to the high diversity of both habitats and wild species in China, biological communities are characterized by a high functional diversity. Butterfly communities are often classified into two functional groups, specialists and generalists. But a finer trait-based classification might be needed for a better understanding of community assembly processes. Here, we used larval diet, voltinism, and dispersal ability to identify functional groups and relate their responses in alpha and beta diversity to gradients in human disturbance, altitude, and resource availability. Across all species, we found a negative impact of anthropogenic disturbance on abundance, a decrease in species richness with altitude, and a positive effect of resource availability. We further found that butterfly communities are best classified into three functional groups: univoltine specialists, bivoltine specialists, and generalists, whereby univoltine specialists showed the strongest dependence on resource availability compared to bivoltine specialists and generalists. Overall beta diversity responded strongly to the effective distance, the mechanisms structuring local communities differed among the functional groups. Univoltine specialists were mainly structured by environmental filtering. Bivoltine specialists were driven by mobility limitation and environmental filtering via resource availability. Generalist species were entirely driven by mobility. Our study highlights the importance of considering multiple functional traits to assess impacts of environmental change on community assembly. This approach enabled us to differentiate between primary ecological processes such as habitat filtering and mobility limitation. We conclude that the conservation of univoltine specialists should be a priority with a focus on targeted habitat management and conservation strategies.