Rearing of Non-Descendant Offspring in an Allodapine Bee, Exoneura bicolor Smith (Hymenoptera: Apidae: Xylocopinae): A Preferred Strategy or Queen Coercion?

In heathland populations of the Australian allodapine bee Exoneura bicolor, the presence of overlapping broods in some colonies creates opportunities for eusocial-like sib rearing. By artificially orphaning colonies in observation nests, we investigated whether sib-rearing by some older daughters occurs in the absence of any potential for coercion by parental females. We found strong evidence for sib-rearing in the absence of parental females in 40% of our nests and weaker evidence in another 40%. Of those colonies with strong evidence of sib-rearing, 65% of such rearing occurred in nests where there was also no opportunity for coercion by adult siblings. These results indicate that sib-rearing in E. bicolor does not require coercion by adult nestmates. A variety of factors that may make sib-rearing a preferred strategy in the absence of coercion are discussed.