Contrasting Patterns of Species Richness and Composition of Solitary Wasps and Bees (Insecta: Hymenoptera) According to Land-use

Several species of arthropods inhabiting forest fragments interact with managed areas. The importance of such areas to biodiversity conservation, however, is not well established. Communities of solitary wasps and bees (Insecta: Hymenoptera) play a key role in agroecosystem functioning and they have been used in studies of biodiversity assessment in different land-use types. We aimed to assess patterns of species richness and composition of solitary wasps and bees over a 1-yr period in a gradient of decreasing land-use intensity formed by pastures, alley croppings, young fallows, and old fallows using trap nests. Old fallows had the highest species richness of wasps and bees, harboring all bee species and 86 percent of wasp species occurring in the region, while the remaining land-uses had similar species richness. Vegetation structure (tree richness) and relative humidity explained most of the variance for the species richness of wasps. For bees, however, there was no influence of environmental factors on the community among land-use types, indicating better adaptability of this group to environmental variations related to land-use. The composition of solitary wasp communities (but not those of bees) differed among land-use types, and the occurrence of rare species in most cases was restricted to old fallow sites. In conclusion, the community of solitary wasps and bees is contingent on land-use, with solitary wasps more sensitive to anthropized areas. For both groups, less anthropized areas harbor a greater richness and number of rare species while more intensively managed land-use types harbor higher abundances.