Relatedness modulates reproductive competition among queens in ant societies with multiple queens

Ant societies may contain multiple queens competing over reproduction. In the ant, Formica fusca, queens adjust their egg laying effort to kinship of their nestmates. Our experiments show that queens increase their egg laying rate when exposed to odors of a highly fecund second queen, but only when this queen is not close kin. When exposed to odors of a highly fecund close relative, queens decrease their egg laying in order to decrease competition. Reproductive sharing in animal groups with multiple breeders, insects and vertebrates alike, contains elements of both conflict and cooperation, and depends on both relatedness between co-breeders, as well as their internal and external conditions. We studied how queens of the ant Formica fusca adjust their reproductive efforts in response to experimental manipulations of the kin competition regime in their nest. Queens respond to the presence of competitors by increasing their egg laying efforts, but only if the competitors are highly fecund and distantly related. Such a mechanism is likely to decrease harmful competition among close relatives. We demonstrate that queens of Formica fusca fine-tune their cooperative breeding behaviors in response to kinship and fecundity of others in a remarkably precise and flexible manner.

Automated summary

In ant societies, multiple queens may compete over reproduction. The study shows that in Formica fusca ants, queens adjust their egg laying rate based on the kinship of their nestmates. When exposed to odor of a highly fecund non-kin queen, queens increase their egg laying rate, while if the queen is a close relative, queens decrease their egg laying rate to reduce competition. This demonstrates that cooperative breeding behaviors in Formica fusca queens are influenced by kinship and fecundity of others.