Life cycle and social behavior in a heathland population of Exoneura robusta (Hymenoptera: Apidae): Habitat influences opportunities for sib rearing in a primitively social bee

Montane populations of the allodapine bee Exoneura robusta Cockerell in southern Victoria, Australia, have been the subject of numerous studies of sociality over the last decade. These populations are univoltine and colonies exhibit a semisocial/quasisocial polymorphism. Synchronous brood development and restricted periods of egg laying in these populations severely limit opportunities for sib rearing by older daughters. Here, we report the life cycle and social behavior of a conspecific subcoastal heathland population from southern Victoria. Colony sizes and intracolony relatedness are lower in the heathland population, possibly because the nesting substrate is relatively short-lived and spatially dispersed. Brood development is relatively rapid at the heathland locality, such that some colonies are able to produce a 2nd brood in late summer. As a result, opportunities for sib rearing frequently occur in heathland E. robusta, allowing for quite different forms of alloparental care than occurs in montane populations. The presence of opportunities for sib-rearing behavior in this species provides evidence of habitat mediation of sociality that is not caused by latitudinal variation.