Evolution of the scale and manner of brother competition in pollinating fig wasps

Abstract

Contest competition and male dispersal have evolved a number of times in pollinating fig wasps. Given their highly female-biased sex ratios and high relatedness between competing males, this phenomenon is surprising. Using a comparative approach, we found a significant association between high adult sex ratios (male:female), fighting and dispersal. We conclude that a relatively high proportion of males could have led to the evolution of fighting and to excess males that avoid kin conflict through dispersal. These wasps respond to increased competition between relatives by altering the scale at which they compete, but also by competing more intensely. In support of the new generation of kin selection models, we found that relatedness of competing males has no effect on the likelihood of fighting. Even so, selection at a higher hierarchical level has selected for dispersal and hence a larger scale at which competition occurs. We found that although the sex ratio gives a rough indication of the mating system it fails to be accurate at a finer scale.