HONEY-BEE COLONIES ARE GROUP-LEVEL ADAPTIVE UNITS

It is not widely recognized that natural selection has produced adapti ve units at the level of groups. Multilevel selection theory shows tha t groups can evolve a high level of functional organization when betwe en-group selection predominates over within-group selection. Strong em pirical evidence that natural selection has produced adaptive units at the group level canes from studies of social insects in which we find colonies in certain species functioning as highly integrated units. T he functional organization of a social insect colony is best understoo d for honey bees. Recent experimental analyses of honey bee colonies h ave revealed striking group-level adaptations that improve the foragin g efficiency of colonies, including special systems of communication a nd feedback control. These findings are reviewed with the aim of showi ng that evolution has produced adaptively organized entities at the gr oup level.