Exploitation of Floral Resources and Niche Overlap within an Oil-collecting Bee Guild (Hymenoptera: Apidae) in a Neotropical Savannah

Oil bees exploit host plants for resources to feed the adults and offspring, as well as for the construction of their nests. The aim of the current study is to investigate how the species in this guild distribute their foraging effort, and the range in their niche overlap levels. Our hypothesis is that niche overlap levels are strongly affected by the exploitation of some key plants, those profitable and locally abundant oil-plants. The bees were sampled for six months, during their visits to the flowers in a savannah (Cerrado). These oil-bee species explored the floral resources provided by 13 plant species. The trophic niche of the most abundant species, Centris aenea Lepeletier, was relatively narrow, similarly to those of Epicharis species. Low overlap of trophic niches (TrNO <= 30%) was most commonly found. The distribution of bee visits to the host plants revealed redundancy in the floral resource exploitation. However, the foraging concentration levels in some key plants were different for distinct oil-bee species, and it contributed to the low overlap of niches between many pairs of species.