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Social insects represent one of the pinnacles of social evolution, and their huge ecological success may be attributable to the sophisticated division of labour and conflict resolution observed in their societies. Eusocial societies exist along a continuum from facultative and primitive (simple) societies in which subordinates retain reproductive totipotency into adulthood, to advanced societies in which the sterile worker caste are committed to their subordinate role. Queenless ponerine ants are unusual, however, exhibiting a simple social structure but having recently diverged from an advanced ancestor. They therefore represent a powerful model system for understanding the roles of evolutionary history, ecology and sociality on behavioural and physiological division of labour. Here, I investigate the influence of reproductive dominance on division of labour and social cohesion in the queenless dinosaur ant, Dinoponera quadriceps. I also present the first description of their natural foraging and nesting ecology. Finally, I investigate the physiological control of division of labour and behavioural plasticity, and explore the relative contribution of conserved and novel genes in the evolution of simple society in this species. Dinosaur ants exhibit remarkable behavioural plasticity despite their advanced ancestry; individual behaviour is strongly influenced by future reproductive prospects and learned aspects of the social environment. They exhibit a discontinuous social hierarchy, in which the reproductive female is transcriptionally distinct from her subordinates, with the largest expressional differences observed in relation to reproductive physiology. Their advanced ancestry is evident both behaviourally and transcriptionally; they exhibit few differences in gene expression within the ancestral worker caste as well as advanced behaviours such as allogrooming, which has been co-‐opted for a role in social cohesion since their reversion to simple society. Dinosaur ants reveal the relative influences of social behaviour and evolutionary history in shaping the behavioural and physiological characteristics of eusocial societies. |
