A cheater lineage in a social insect: Implications for the evolution of cooperation in the wild.

Biological cooperation is vulnerable to cheaters that exploit the benefits of cooperation without contributing to these benefits, thus the control of cheating is important to maintain cooperative systems. Recently, we reported a cheater lineage in a field population of the Japanese ant Pristomyrmex punctatus. This species is characterized by its asexual reproduction and lack of a division of labor: all females fulfill both reproduction and cooperative tasks in their colonies. Cheaters that originated from cooperators lay more eggs and take little part in cooperative tasks, resulting in lower fitness of their nest mates. This leads to contrasting selection pressures between the individual and group levels, and makes the cheater ants analogous to cheaters in social microbes and cancer cells. The genetic and developmental basis, possible transmission strategies, and evolutionary fate of the cheaters are discussed in the context of the origin and persistence of cheating and cooperation in nature.