Cooperation is one of the major problems in evolutionary biology. It has been mainly considered in the context of controlling cheating. Inclusive fitness theory predicts that high relatedness can inhibit cheating. However, cooperation itself is a collective function, which is not always optimized by high relatedness and often requires collaboration between genetically different entities.

The ant Pristomyrmex punctatus provides a unique opportunity to investigate the relationship between the genetic composition and the effectiveness of cooperation. In this ant, all nestmates fulfill both parthenogenetic reproduction and cooperative tasks. This ant is also known to harbor a cheater lineage which lowers fitness of their nestmate cooperators.

Using microsatellite markers, we revealed that the colonies vary in the genetic composition, most of which would be achieved through drifting of individuals among colonies. Although it allows the cheaters to intrude, the acceptance of alien individuals might also facilitate collaboration between genetically different cooperators. Indeed, we found that the genetic heterogeneity of the cooperators had a significantly positive effect on the colony productivity, but only at one microsatellite locus. While the mechanism remains unclear, this result suggests that the effects of genetic composition should be assessed at each locus.