Effects of forest trails on the community structure of tropical butterflies

Abstract

Understanding the ecological impacts of human disturbances is essential for the formulation of conservation strategies. This study aimed to investigate if unpaved trails (with about 5 to 6 m wide) inside forests can cause ecological changes in their surroundings. The studied group was the fruit-feeding butterflies, since they usually respond to habitat disturbances through changes in species composition. This group is also known to present a distinct distribution along a vertical gradient in tropical forests. However, in open areas, some canopy species are observed reaching the ground. Based on that, we address the following hypotheses: (1) trails inside the forest cause a disruption in the vertical stratification pattern of fruit-feeding butterfly assemblages, and (2) trails modify their community parameters. The study was carried out in a protected area in the Atlantic Forest. Butterflies were sampled monthly through 2 years with bait traps distributed in the canopy and the understory in two habitat types: (1) forest interior, and (2) edges parallel to a trail opening. Our results showed that the understory edge had a greater abundance of individuals and lower species richness when compared to the forest interior. However, the trails did not disrupt the vertical stratification pattern or modify the species composition of fruit-feeding butterflies. Therefore, their effect was not as strong as other types of human disturbances. The present results suggest trails inside forests presented a relatively low impact in the adjacent biological communities, preserving the habitat for several forest organisms and maintaining the vertical structure of biological communities along them.