Effects of riparian forest degradation on communities of fruit-feeding butterflies (Lepidoptera: Nymphalidae) in Eastern Brazilian Amazonia

Introduction: Frugivorous butterflies are highly sensitive to changes in habitat quality, making them important indicators of environmental disturbance. Despite their diversity, little is known about how they respond to riparian forest degradation in urban areas of Amazonia. Objectives: To assess patterns of species richness, diversity, and abundance of frugivorous butterflies, in relation to vegetation structural variables related to forest degradation. Methods: The samplings of the community of frugivorous butterflies and the structure of riparian vegetation were carried out in 20 riparian areas, selected based on a continuous degradation gradient measured by canopy openness. Sampling was carried out using a 150 m transect with six baited traps installed on each riverbank. Vegetation structure was assessed using one 60 × 10 m plot and two 4 × 4 m subplots on each side of the river. Species richness, abundance, and butterfly diversity were quantified, and their relationships with vegetation variables were analyzed. Results: A total of 2 379 individuals were recorded, belonging to 54 species and morphospecies. Total abundance per site ranged from 24 to 387 individuals, while species richness (q0) varied from 9 to 28 species. Common (q1) and dominant (q2) species richness ranged from 5.7 to 18.5 and from 2.8 to 14.8, respectively. Species richness increased with canopy openness, while the effective numbers of common (q1) and dominant (q2) species were positively associated with both canopy openness and variation in tree and palm diameter (cvD). Butterfly abundance also increased with canopy openness but decreased with increasing structural heterogeneity. Conclusions: Riparian forests in anthropogenic landscapes remain important for frugivorous butterfly conservation when vegetation structure is preserved. Increasing degradation favors generalist species, whereas rare and specialized species are associated with more conserved sites. Canopy openness was the main predictor of butterfly diversity and composition, highlighting the importance of conserving and restoring riparian forests in the Eastern Amazon and reinforcing the value of butterflies as bioindicators.