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

Keywords: animal personality behavioural syndrome division of labour social spiders task specialization temperament 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. While it has long been recognized that individuals vary in traits including behaviour, burgeoning research seeks to explain the causes and consequences of consistent individual differences in behaviour across time and contexts, a phenomenon known as an-A fundamental evolutionary question is how within-population variation in personality is maintained in the face of selection for optimal behav-ioural phenotypes or high plasticity (Krebs & Davies, 1997; Sih et al., 2004). Theoretical models have proposed a variety of mechanisms for the persistence of alternative behavioural types (Dall, Houston, An important but understudied factor in the ecology and evolution of individual differences is the social environment, which may influence both the expression and fitness outcomes of behavioural variation and consistency In animals ranging from guppies to ants, social groups composed of a mix of personality types (e.g. boldeshy, aggressiveedocile) have been shown to outperform relatively homogenous groups, as measured by colony productivity A possible benefit of diverse social composition is that group members with different personalities specialize on different roles or tasks, facilitating di-Division of labour is thought to be a key adaptation in social insects, where it has been studied most intensely Here we ask, what is the role …