The influence of sociality, caste, and size on behavior in a facultatively eusocial bee

Abstract

Social cooperation requires increased tolerance of other individuals. We used social and solitary individuals of the facultatively eusocial bee Megalopta genalis to compare interactions with non-nestmate individuals in a standardized behavioral assay, a circle tube. We set up interactions between bees from different nests matched for caste (solitary, social: queen or worker). We found more tolerance in social than solitary pairs, but found no difference in aggression. We also found that workers continued expressing caste-typical behavior even when matched against other workers from different nests. However, there was no difference in expression of queen-typical behaviors between the three groups. Our data on social caste show that outside of the queen–worker social context, both queens and workers express similar levels of queen-like behavior. However, workers still express higher levels of worker-like behavior than do queens. We found no effect of variation in ovary size on behavior. We found that body size correlated positively with queen-like behaviors, and negatively with worker-like behaviors. Our body size data suggest that the worker phenotype may result from naturally occurring size-correlated variation in behavior, combined with maternal manipulation of both body size through nutrition and behavior and ovary development through social aggression.