Facultative social parasitism in the allodapine bee Macrogalea berentyensis

Previous research on social parasitism has largely ignored allodapine social parasites, which is surprising given the huge potential of these bees to provide a better understanding of social parasitism. Macrogalea berentyensis, a species that was previously suggested to be a social parasite, was collected in nests of M. ellioti, and also in nests consisting of only M. berentyensis. These findings, along with morphological and phylogenetic evidence, show that this species is a facultative social parasite. In the independently living M. berentyensis nests, brood were present that had been reared to an advanced stage, suggesting that: (i) these parasites may be effective at foraging and caring for their brood; or (ii) these nests may be colonies where all the hosts had died, and these parasites had yet to disperse. Macrogalea berentyensis is the closest relative of the facultative social parasite, M. antanosy, and both these species represent the most recent evolutionary origin of social parasitism within the allodapines. Further behavioral research on both these parasitic species would therefore have important implications for the understanding of the evolution of social parasitism.