Urban fragment of the Atlantic Rainforest as a refuge for cavity-nesting bees and wasps (Hymenoptera: Aculeata)

Abstract

ABSTRACT Due to the fragmentation of many natural habitats, urban areas have become important refuges for various species, including bees and wasps. The present study aimed to determine the species composition, richness, and abundance of solitary bees and wasps that nest in pre-existing cavities in an urban fragment of the Atlantic Rainforest in the city of Salvador, Brazil. Data on the occupancy of the trap-nests and offspring mortality are also reported. The study was conducted at the Parque Zoobotânico Getulio Vargas (PZBGV) and the campus of Universidade Federal da Bahia (UFBA), the areas of which form the urban fragment. Traps were inspected once a month for 2 years. The composition and diversity of bee species were similar between the areas, but richness and abundance of wasp species were higher at UFBA. Centris analis (Fabricius) was the most abundant bee species in both areas, and Podium denticulatum (Smith) and Trypoxylon sp.2 were the most abundant wasp species at UFBA and PZBGV, respectively. Most nesting of these species occurred in the warm season. Centris analis and Trypoxylon sp.2 preferred traps made of cardboard, whereas P. denticulatum was the most generalist species, occupying all types of trap-nests. The main factor of mortality among immature specimens was ‘unknown cause’ for both bees and wasps. Only three species of natural enemies emerged from nests of C. analis. The increase in the richness of bee and wasp species in comparison with the results showed in previous studies made in the same areas indicates that the fragment offers valuable nesting places for species of cavity-nesting bees and wasps and can ensure the maintenance of these insects.