Genetic and behavioral conflict over male production between workers and queens in the stingless bee Paratrigona subnuda

Abstract.

Though social-insect colonies are highly cooperative, conflicts of interest can sometimes occur. In this study, we examined conflicts over male production in the stingless bee, Paratrigona subnuda. Microsatellite genotyping of workers confirmed that the queen was always singly mated, as in other stingless bees. As a consequence, workers are more related to the sons of other workers than they are to the queen's sons, and conflict is expected with the queen over who produces the males. A likelihood analysis shows that both the queen and the workers contribute substantially to male production, with workers typically contributing more, an average of 64%. The likelihood curves are sharp enough to show that the worker fraction varies among colonies and over time, consistent with a shifting balance of power between queen and workers. Workers laid eggs in 31% of cells recently oviposited in by the queen, and in some other cells as much as 1–2 days old. Queens sometimes forcefully pushed a laying worker from the cells, but the worker returned to finish laying. There was no evidence that queens were effective in preventing workers from laying eggs, yet queens produce some of the males. Worker behavior during oviposition suggests that they do not discriminate between cells destined to produce queen males versus workers, and thus the cost of losing too many future workers may limit worker laying.