Forest loss or fragmentation per se? Drivers of Nymphalidae butterfly diversity in fragmented landscapes

Land-use changes driven by agriculture and urbanization are major causes of biodiversity loss, especially in tropical regions where deforestation rates are highest. These transformations lead to habitat loss and fragmentation, reducing the size and connectivity of native habitats. Landscape modifications also alter local forest structure, and these factors may synergistically influence biological diversity. We examined how landscape forest cover and fragmentation per se (i.e. fragmentation independent of habitat loss), together with local habitat structure, influence the diversity of Nymphalidae butterfly communities in remnants of the Atlantic Forest. We evaluated whether trophic guild (nectar- vs. fruit-feeding) and habitat affinity (forest-dependent vs. disturbance-adapted) mediate these responses. Using entomological nets, we sampled butterflies in 17 forest fragments in the Brazilian Atlantic Forest. We used the percentage of native forest cover, edge density, number of surrounding forest fragments, and tree height and DBH as predictors. Species richness and diversity were primarily explained by landscape forest cover, which negatively affected nectar-feeding and disturbance-adapted species. In contrast, butterfly abundance was mainly driven by fragmentation per se, which had a positive effect on most groups, except for forest-dependent species, whose abundance was unaffected. Our findings underscore the importance of considering landscape-scale processes and multiple ecological dimensions when evaluating butterfly responses to habitat changes. The study also highlights the ecological value of forest fragments in highly human-modified landscapes and underscore the importance of considering both forest loss and fragmentation per se in conservation planning.