Queuing for dominance: gerontocracy and queue-jumping in the hover wasp Liostenogaster flavolineata

The mechanisms through which dominance is inherited within social groups vary from direct interactions such as fighting to non-confrontational conventions. Liostenogaster flavolineata is a primitively eusocial hover wasp in which one female, the ‘dominant’, is the only reproductive upon the nest. The remaining females, although capable of reproduction, behave as helpers. In this study, we investigate the rules by which helpers inherit dominance. We removed successive dominants from 56 nests and recorded accession on un-manipulated nests. The results showed that L. flavolineata has a strict age-based inheritance queue: new dominants are the oldest female in their groups 87% of the time. Thirteen cases of queue-jumping were found in which young individuals were able to supplant older nestmates and inherit dominance precociously. Queue jumpers did not differ from other wasps in terms of relatedness to other group members or body size. Individuals that had previously worked less hard than other females of equivalent rank were significantly more likely to later jump the queue. Queue-jumping may represent a cheating strategy or could indicate that the rule for inheriting dominance is not based purely on relative age. We also discuss possible reasons why age-based queuing has evolved and its potential to promote the evolution of helping behaviour.