Cavity-nesting bees and wasps (Hymenoptera: Aculeata) in a semi-deciduous Atlantic forest fragment immersed in a matrix of agricultural land

Abstract

Cavity-nesting bees and wasps (Hymenoptera: Aculeata) have been showed to be suitable models to investigate the effects of forest fragmentation and human land use. Those studies are particularly pertinent when considering fragmented ecosystems such as the Atlantic semi-deciduous forest in Brazil. We investigated the changes in composition, nest abundance, and mortality of cavity-nesting bees and wasps over edge-center forest fragment immersed in a matrix of agricultural lands in southeastern Brazil. Trap-nests (bamboo canes and cardboard tubes) were set in nine sampling stations in three different zones in the study site: three sampling stations at the forest edge; three at 250 m away from the edge and another three at 500 m away from the edge. Nests were monitored monthly for 2 years (from June 2011 to May 2013). A total of 942 nests (706 built by 16 bee species; 236 from 18 wasp species) were collected in the fragment. A significant change over gradient edge-center was observed on the parameters analyzed. The Non-metric Multidimensional Scale analysis showed that 72% of the species (host and natural enemies) that present more than ten records were associated with the forest edge. Furthermore, the highest values of the abundance of nests, parasitism, and mortality were recorded in the edge. In spite of being surrounded by farmlands, the fragment hosts a great diversity of trap-nesting wasp and bee species. Our findings demonstrate that forest edges are important habitats to maintain communities of cavity-nesting bees and wasps.