Influence of the edge-core gradient on the scorpion assemblage (Arachnida, Scorpiones) in a Brazilian Atlantic forest

Abstract

Habitat structure plays a major role in the distribution of species in a given area. Edge-core gradients may be useful for examining the effects of habitat modifications, as they represent changes in habitat structure at a small spatial scale. Here, we analyzed how scorpion assemblages were affected by variations in habitat structure along an edge-core gradient in a Brazilian Atlantic forest fragment. Scorpions were collected during 20 months (May 2007 – December 2008) in 112 pitfall traps, arranged from the fragment edge to 500 m inside the forest interior. All pitfall traps were checked in each two days with all scorpions found being collected. We also measured eight environmental variables along the edge-core gradient: canopy cover, leaf litter depth, diameter at breast height (DBH), plus the densities of fallen logs, stones, trees, shrubs, and bromeliads. We collected a total of 767 scorpions, all within the Buthidae family, and five species were identified (Ananteris mauryi, Tityus brazilae, T. neglectus, T. pusillus, and T. stigmurus). The abundance of these arachnids was positively influenced by habitat structure, with more individuals occurring in areas with trees having higher DBH values. However, species richness and composition were not affected by any of the environmental variables. Our results suggest that, at small spatial scales, scorpion assemblage (i.e. abundance) is sensitive to changes in habitat structure. Here, we have highlighted the importance of habitat structure for the maintenance of scorpion assemblages in their habitats.