Division of labor in a dynamic environment: response by honeybees (Apis mellifera) to graded changes in colony pollen stores

A fundamental requirement of task regulation in social groups is that it mu st allow colony flexibility. We tested assumptions of three task regulation models for how honeybee colonies respond to graded changes in need for a s pecific task, pollen foraging. We gradually changed colony pollen stores an d measured behavioral and genotypic changes in the foraging population. Col onies did not respond in a graded manner, but in six of seven cases showed a stepwise change in foraging activity as pollen storage levels moved beyon d a set point. Changes in colony performance resulted from changes in recru itment of new foragers to pollen collection, rather than from changes in in dividual foraging effort. Where we were able to track genotypic variation, increases in pollen foraging were accompanied by a corresponding increase i n the genotypic diversity of pollen foragers. Our data support previous fin dings that genotypic variation plays an important role in task regulation. However, the stepwise change in colony behavior suggests that colony foragi ng flexibility is best explained by an integrated model incorporating genot ypic variation in task choice, but in which colony response is amplified by social interactions.