Unrelated helpers in social wasps

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The evolution of sociality is one of the major transitions in evolutionary biology. The key testing-grounds for theories concerning the origin of helping are primitively eusocial taxa in which the option of independent reproduction still exists. Social groups of Polistes paper wasps comprise groups of females in which one 'dominant' female lays most or all of the eggs while the others ( 'helpers') forage to feed the dominant's larvae. Yet despite Polistes being the best studied primitively eusocial system, it remains unclear why many females choose to become helpers rather than build their own nests and reproduce independently. Especially paradoxical are populations of P. dominulus, in which >30% of helpers are unrelated to the dominant egg-layer in the group. Unrelated helpers cannot transmit their genes indirectly by rearing offspring of the dominant (kin selection), and so must attempt to obtain direct fitness by laying eggs themselves. The proposed research will use a combination of large-scale field experiments and genetic work to investigate the reproductive strategies of unrelated females in a Spanish population of P. dominulus. The work will: (1) Estimate the reproductive success of unrelated foundresses, focussing particularly on reproduction through inheritance of the egg-laying position, a route that has been strikingly neglected in previous studies of primitively eusocial insects. (2) Separate the effects of kin selection and direct fitness benefits by comparing unrelated helpers with helpers that are sisters of the dominant in terms of: (i) helping effort; (ii) position in the queue to inherit the dominant egg-laying position; (iii) aggression in unmanipulated colonies; (iv) aggression at the critical moment when the dominant is replaced. The overall result will be the most comprehensive evaluation of the basis of helping in a primitively eusocial insect, and the first clear separation of how kin selection and direct fitness benefits influence individual behaviour.