Individual differences in personality and behavioural plasticity facilitate division of labour in social spider colonies

Among factors hypothesized to favour consistent individual differences in behaviour (i.e. personality or behavioural types), the social environment has received relatively little attention. Within-group variation in personality may facilitate the emergence of division of labour, if individuals with different personalities tend to specialize on different tasks. In turn, functional benefits derived from division of labour may promote the coexistence of alternative behavioural types. We investigated how intracolonial variation in personality influences individual and collective patterns of task performance in the social spider Anelosimus studiosus. Colonies composed of a mixture of aggressive and docile females showed greater nonreproductive division of labour than monotypic colonies of either behavioural type. Within mixed-personality colonies, aggressive individuals tended to perform more prey capture, colony defence and/or web repair, while docile individuals became brood care specialists. Task differentiation was shaped by social dynamics, but behavioural plasticity varied with personality type: docile individuals were more socially responsive, shifting their task allocation in the presence of aggressive colonymates. Efficiency gains from personality-linked division of labour may help to explain the superior performance of diverse colonies and to maintain individual behavioural variation in A. studiosus and other social species.