Microhabitat changes induced by edge effects impact velvet ant (Hymenoptera: Mutillidae) communities in southeastern Amazonia, Brazil

Abstract

Pervasive changes in land use combined with the effects of climate change are a major threat to biodiversity in the arc of deforestation, a region at the Amazonia–Cerrado transition in Brazil. In this region, we investigated edge effects evidenced by microhabitat and microclimate changes upon the diversity and organization of velvet ant communities. We selected two forest edges with different histories of deforestation (8 and 28 years-old). From each edge, we placed arrays of pitfall traps along a 0.5 km linear transect towards the preserved forest interior. In each array, we recorded microhabitat variables to characterize transects. Over the period of a month, we collected 1073 velvet ants from 30 species. Along the 28 year-old transect we found twice as many logs, less canopy cover and higher shrub density, associated with higher variation in air temperature, than the 8 year-old transect. Velvet ant abundance, richness and evenness were significantly higher in the 28 year-old transect. In both transects, the abundance of velvet ants was highest on the edges and declined towards the forest interior. Environmental variation correlated with time since deforestation and with proximity to the edge affected the organization of velvet ant communities. This can be due to colonization of species from the open habitat matrix and loss of species associated with the forest interior. The combination of deforestation and microclimate change in southeastern Amazonia may alter the structure of insect communities and generate consequences through cascading effects and alterations of ecosystem services provided.