Social networks and social environment in a facultatively social bee

The eastern small carpenter bee Ceratina calcarata is a facultatively social bee. In social nests mothers frequently produce a small under-provisioned daughter who forages on behalf of her regular siblings to prepare them for overwintering, which this worker-daughter does not herself survive. To understand how this simple division of labour, between mothers, worker-like daughters, and regular daughters, is determined we studied social networks within colonies of differing social composition. Observation nests were constructed from wild established nests, with control nests possessing mothers and worker-like daughters, and two treatments manipulating social environment were applied, 1) removing mothers, and 2) removing mothers and worker-like daughters. Behaviours were scored from video and pairwise interactions were analyzed using social interaction networks. Within observation nests it is expected that nests possessing worker-like daughters will exhibit interaction networks of low connectivity, with mothers, worker-like daughters or foraging regular daughters being hub individuals, as they provision nestmates. In colonies lacking mothers and worker-like daughters, thus lacking size-based hierarchy, it is expected that interaction networks will be highly connected, and repeated aggressive encounters will establish hierarchy and food sharing roles in the nest. Insights into such simple social systems advance our understanding of sibling cooperation and competition, as well as maternal care. Understanding such dynamic cooperative behaviours may also suggest plausible scenarios by which both differences in physiology and behaviour in otherwise solitary species may have set the stage for advanced eusociality.