Spatial distribution of a primitively social bee: does genetic population structure facilitate altruism?

Exoneura bicolor is a univoltine, facultatively social bee exhibiting a solitary/quasisocial/semisocial colony polymorphism. Intracolony relatedness in semisocial colonies has been previously estimated at 0.49 ± 0.06, although the crucial relatedness between altruists and the brood that they rear will be about half this value. Population structure and intracolony relatedness were investigated in 7 localities in S Victoria, Australia, to determine if inbreeding at any level of population structure was contributing to relatedness between altruists and beneficiaries within these colonies. Inbreeding was not contributing to between-group genetic variance, at any level, in a consistent manner across localities: relatedness, considered in isolation, does not seem sufficient to account for the presence of worker behavior. Significant heterogeneity among localities for all F-statistics; this may be attributable to stochastic elements such as cofounding behavior and the low percentage of males in the brood.