Winter is coming: harsh environments limit independent reproduction of cooperative-breeding queens in a socially polymorphic ant

Animals that live in cooperative breeding groups frequently inhabit harsh environments. It is widely accepted that harsh environments hinder independent reproduction, and this constraint favours individuals staying in family groups. Yet the assumption that harsh ecological conditions reduce the success of members of cooperative breeding groups when breeding independently has not been experimentally tested. We addressed this shortcoming using the socially polymorphic Alpine silver ant, Formica selysi. This species has single-queen (independent breeders), and multiple-queen (cooperative breeders) colonies coexisting within populations. We placed newly mated queens emerging from each type of colony to breed alone in either a harsh or mild winter condition and recorded their brood production and survival. Queens emerging from single-queen colonies were unaffected by the winter condition and had higher survival and larger broods than queens from multiple-queen colonies. In contrast, queens f...