Cooperative nesting and ovarian development in females of the predominantly social bee Exoneura Bicolor Smith (Hymenoptera: Anthophoridae) after forced solitary eclosion

Cooperative nesting is frequent in montane populations of the Australian allodapine bee Exoneura bicolor. In natural populations, multifemale colonies primarily arise from cooperative re‐use of natal nests or by the cofounding of new nests by groups of female relatives. In this study we examine ovarian enlargement of females that are artificially placed in solitary nests prior to adult eclosion. After eclosion, females were allowed to move around freely prior to overwintering. Of the females recovered at the end of our experiment, 74% had joined to form either 2 or 3‐female colonies. We found no evidence of ovarian inhibition between colony members. However, inseminated females showed significantly greater ovarian development than their uninseminated nestmates. These results indicate that the benefits of cooperative nesting are great, even when nestmates are unrelated. This may have consequences for kin selection models of altruism in Australian allodapine bees.