Strong selection on a gene that influences reproductive competition in a social insect

COMPETITION among nestmate females for reproductive opportunities is a fundamental property of insect societies, the outcome of which defines the form of colony social organization and the nature of subsequent social evolution1–3. Several factors influencing the outcome of competition among potential reproductives have been identified in eusocial Hymenoptera, including age4, size5–7 and degree of ovary or exocrine gland development7–10. In no case is the genetic basis of traits associated with success in these social contests understood, although there is a heritable component to their expression in laying worker honey bees11. I report here the existence of a single mendelian factor that strongly influences success in reproductive competition in multiple-queen societies of an ant, and I also propose a mechanism by which variation is maintained at this gene despite the presence of strong directional selection.