Ecological and functional effects of habitat conversion and seasons on fruit-feeding butterfly assemblages in tropical dry forests

Abstract

Tropical dry forests have been increasingly impacted by anthropogenic disturbances, affecting both plant and animal communities. Our study examined how land-use change for pasture establishment and seasonal variation influence taxonomic (species richness and Shannon index), functional and phylogenetic diversity, as well as instability in development due to fluctuating asymmetry (FA) of the wings in fruit-feeding butterfly assemblages (Nymphalidae). Butterflies were sampled using Van Someren-Rydon traps in three mountain ranges of the Jacobina mountain complex, Bahia, Brazil. Sampling was conducted during two distinct periods, the wet and dry seasons. A total of 1092 individuals (36 species) were recorded. Of these, 222 well-preserved individuals (32 species) were selected for morphometric analyses. Flight-related functional traits were measured, including thorax length and width, forewing length, width and area, as well as wing FA. Most functional traits exhibited weak phylogenetic signal, indicating that environmental filtering operates largely independently of shared ancestry. Seasonal dynamics, rather than habitat differences, drove increases in thorax width and wing dimensions during the wet season. Taxonomic and functional diversity were higher during the wet season than in the dry season, likely due to more favourable environmental conditions and increased resource availability. Pastures harboured lower phylogenetic diversity and higher wing FA than forests. Together, these patterns indicate that seasonality primarily shapes functional structure, while habitat conversion promotes phylogenetic homogenization and reduces developmental stability. Our study reinforces the effectiveness of fruit-feeding butterflies as environmental indicators and underscores the importance of using multiple diversity and functional metrics to assess ecosystem integrity.