Intra-colony relatedness and sociality in the allodapine bee Exoneura bicolor

Overwintered and newly co-founded nests of Exoneura bicolor exhibit different grades of sociality. Intra-colony relatedness was estimated for adults and female brood in both nest types using allozyme data and a multiallelic estimator. The higher relatedness among female brood from overwintered nests compared to newly-founded nests is consistent with the difference in sociality between these colony types (semisocial versus quasisocial). However, intra-colony relatedness among adults is higher in cofounded nests than in overwintered nests, suggesting that differences in sociality are determined by benefit/cost ratios associated with non-reproductive strategies, rather than relatedness between interactants. Rapid egg-production in newly founded nests allows eggs to be 'stockpiled'. This reduceds the tasks available to non-reproductives in early phases of colony development and limits the payoffs available for reproductive altruism. It is suggested that the social flexibility characteristic of allodapines is a consequence of communal progressive rearing which allows many benefits from cooperative nesting to be gained without worker sterility.