The Cavity-Nesting Bee Guild (Apoidea) in a Neotropical Sandy Coastal Plain

Abstract

Some solitary bees establish their nests in preexisting cavities. Such nesting behavior facilitates the investigation of their life history, as well as the monitoring of their populations in natural, semi-natural and cropped habitats. This study aimed to evaluate the acceptance of artificial substrates by cavity-nesting bees in a heterogeneous landscape. We investigated the percentage of occupation of the different trap-nests, the monthly fluctuations in the nesting activity, offspring sex ratio, mortality and parasitism, in two phytophysiognomies: herbaceous-shrub restinga (site 1) and arboreal restinga (site 2). We used as trap-nests, bamboo canes, large and small straws of cardboard inserted into solid wooden blocks. Five bee species established 193 nests, from which 386 adults emerged. Centris tarsata Smith was the most abundant species. Large straws were signifi cantly more occupied than small straws (χ² = 19.951; df = 1; p < 0.0001). Offspring mortality rate for unknown reasons was signifi cant diff erent between sites, 11% (site 1) and 20% (site 2) (χ² = 4.203; df = 1; p = 0.04). The cavity-nesting bee guild had similar composition in both phytophysiognomies, there was a similar rate of occupation of trap-nests in both sites, as well as dominance of C. tarsata nests. Offspring mortality and parasites attack rates seem to be the more distinctive aspects between the herbaceous shrub and arboreal restinga sampled. Our study indicated that remnant fragments of coastal native habitats may be important nesting sites for the maintenance of bee populations, some of which have been indicated as candidates for management as pollinators of cultivated plants in Brazil.