Past Research

Conflict over male production in stingless bees

The social insects provide one of the best models for studying the evolution of cooperative behavior. Kin selection theory explains why a social insect might help relatives instead of trying to reproduce alone, but a more difficult problem remains unsolved. Individuals, once in groups, should often be selected to prefer being a reproductive rather than a helper. But if this is so, why is reproduction so often limited to one queen (or a few queens), particularly in large colonies where the queen cannot hope to physically dominate all her subordinates? A promising, but largely untested, hypothesis is that average or collective worker interests determine who reproduces, including the possibility that workers often supress each other.

The best test of this theory to date is in the honey bee, where extreme multiple mating by the queen causes workers to be more related to her sons than to the sons of other workers. The Strassmann/Queller group will study worker preferences with respect to male production in a related group, the stingless bees (Apidae: Meliponinae). They have previously found that stingless bee queens are generally singly mated, which causes workers to be less related to the queen's sons than to each others¹ sons. The theory of collective worker control therefore predicts that stingless bees will differ from honey bees: workers should lay the male-destined eggs in stingless bees. We will therefore study conflict over who produces the males, and determine who actually does produce them in a number of stingless bee species.

For each species, genotypes of highly variable microsatellite loci will be used to confirm that the queen is singly mated, and to determine the fractions of males derived from the queen and from workers. These results will be related to behavioral observations of conflict during the cell provisioning and oviposition process of each species, a period of highly ritualized behaviors that varies extensively among species. We will test the hypothesis that behavioral conflict is highest in species where both queens and workers produce some of the males, less high in species where both parties can produce males but only one does, and lowest in species where workers cannot produce males. Within each species, they will also test the hypotheses that conflict is higher during times of male production, and that conflict is higher during the provisioning of normal cells (which could produce males or workers) than during provisioning of queen cells.

This research is expected to reveal much about the expression and resolution of genetic conflicts of interest, a topic of importance not only for social insects, but also for other other social organisms, and for other levels of biological organization.