Edge effects on ant diversity and functional composition in a forest fragment in the Central Amazon

Abstract

The process of human-induced forest fragmentation increases the degree of isolation and causes biodiversity loss. Abrupt changes occur mainly near the edge of the fragment, where the average temperature is relatively higher and the humidity is lower. However, some natural environmental characteristics, such as higher air moisture in riparian areas, may buffer or minimize the edge effects. Here, we studied how the edge effect may affect ant species diversity and functional composition on valleys dissected by small streams (mesic areas). We categorized ant assemblages into the functional groups based on foraging, nesting habits, natural history information, and phylogeny. Ants were sampled using pitfalls and the Winkler extractor in ten riparian plots in a fragment of the Central Amazon. We individually fit the ant species richness, occurrence, and composition against two edge measures: forest edge distance and road-building distance. We recorded 99 species/morphospecies. Forest edge distance and road-building distance did not influence the occurrence and number of ant species per plot but were related to ant species composition. Moreover, there was not a clear pattern between functional groups distribution, except by leaf-cutters and generalist omnivorous species. Our results suggest a limited effect of forest edge distance and road-building distance on ant diversity