Impact of Habitat Changes on Butterfly Diversity in the Forest–Grassland Ecotone in the Source of the Bailong River, Western China

Abstract

Simple Summary To explore the impacts of habitat change on butterfly communities and their variation along the elevational gradient in the forest–grassland transition zone of the Bailong River source area, we carried out transect surveys over three consecutive years (2022–2024). Our key findings are: (1) The butterfly community exhibited typical alpine grassland assemblage characteristics, dominated by Nymphalidae (60.0%), followed by Pieridae (23.7%). Papilionidae and Hesperiidae represented only small fractions, at 0.7% and 0.5%, respectively. (2) This ecotone showed pronounced habitat edge effects, and the forest-edge shrub habitat harboured the highest species richness. (3) Butterfly assemblages had low species-composition similarity across different habitats. (4) Butterfly species diversity displayed a distinct double-valley pattern in their vertical distribution. (5) Parnassiinae species living in high-elevation alpine meadows are highly threatened by climate change. They should be set as priority conservation targets for future biodiversity management in the Bailong River source area.