Distance from Edge Determines Fruit-Feeding Butterfly Community Diversity in Afrotropical Forest Fragments

We studied the impact of forest edges on the fruit-feeding butterfly communities of three forest remnants in Ghana, West Africa. Community diversity was assessed using traps baited with fermenting banana. Two 200-m, edge-to-interior transects of five traps each were established in each forest. Sampling spanned 1 yr for a total of 180-210 trap days per site and resulted in 2,634 specimens and 56 species. We found significant support for an effect of forest edge on butterfly diversity. The impact of distance from edge on point estimates of diversity, i.e., total trap captures, weighted species richness, and Simpson's diversity, was unique to each forest. Multivariate analyses, which integrated species composition along with relative abundance and richness, uncovered two broad community types, interior communities (those 100, 150, and 200 m distant from the edge) and exterior communities (edge communities and those 50 m distant), indicating that edge habitat generally extends at least 50 m into the forest. However, effects of edges on community diversity were still detected as far as 100 m into the forest. Three species relatively tolerant of forest degradation emerged as indicators of edge habitat. No species were indicative of core habitat.