How forest-grassland mosaics structure fruit-feeding butterfly assemblages in the Pampa biome

Forest-grassland mosaics create strong environmental contrasts, influencing species distribution in biomes like the Pampa of Southern Brazil. This study assessed how these mosaics structure fruit-feeding butterfly (Nymphalidae) assemblages in the region, investigating richness, abundance, and composition in forest and grassland habitats across six localities. Our results show that forest habitats generally support higher richness and abundance, and harbor distinct butterfly communities compared to grasslands. Species composition segregated clearly between the two habitats, reflecting differences in environmental conditions, structural complexity, and resource availability. Forests supported more functionally diverse assemblages due to vertical stratification and microclimatic heterogeneity, although local disturbances like cattle grazing and flooding could impact diversity. The dominance of the Satyrini tribe, particularly in disturbed forest fragments, suggests that anthropogenic impacts simplify forest structure, favoring disturbance-tolerant species. Grasslands were also dominated by disturbance-tolerant Satyrini adapted to open conditions. The study demonstrates that habitat type strongly structures fruit-feeding butterfly assemblages and how this group has the potential to serve as effective bioindicators for monitoring the impacts of land use in this heterogeneous landscape. Implications for insect conservation : Findings emphasize the urgent need to integrate both forest and grassland habitats into conservation policies, as each supports unique and distinct butterfly assemblages, collectively reflecting the ecological complexity of the Pampa biome.