Enforcement of reproductive synchrony via policing in a clonal ant.

In insect societies, worker policing controls genetic conflicts between individuals and increases colony efficiency. However, disentangling relatedness from colony-level effects is usually impossible. We studied policing in the parthenogenetic ant Cerapachys biroi, where genetic conflicts are absent due to clonality and reproduction is synchronized through stereotyped colony cycles. We show that larval cues regulate the cycles by suppressing ovarian activity and that individuals that fail to respond to these cues are policed and executed by their nestmates. These individuals are genetically identical to other colony members, confirming the absence of intracolonial genetic conflicts. At the same time, they bear distinct cuticular hydrocarbon profiles, which could serve as proximate recognition cues for policing. Policing in C. biroi keeps uncontrolled reproduction at bay and thereby maintains the colony-level phenotype. This study shows that policing can enforce adaptive colony-level phenotypes in societies with minimal or no potential genetic conflicts. In analogy to immunosurveillance on cancer cells in genetically homogeneous multicellular organisms, colony efficiency is improved via the control of individuals that do not respond properly to regulatory signals and compromise the functioning of the higher-level unit.