REPRODUCTIVE CONFLICTS AND LEVELS OF SELECTION IN THE ANT PRISTOMYRMEX PUNGENS - CONTEXTUAL ANALYSIS AND PARTITIONING OF COVARIANCE

Phenotypic selection on individual- and colony-level characters was examined in the myrmicine ant Pristomyrmex pungens by contextual analysis and partitioning of covariance. Pristomyrmex pungens has an extraordinary social system in which there are no queens and workers reproduce parthenogenetically. All workers can be reproductive and live only one year in this species. Thus, the annual colony growth rate measures the mean individual lifetime reproductive success. Within-colony individual variation in reproductive activity was estimated From individual ovarian development and revealed conflicting selection on worker dimorphism. Large workers are sporadically found in some colonies and had higher fitness on a within-colony level. However, large workers reduced a colony's fitness at the between-colony level. Therefore, large workers probably exist as a socially parasitic phenotype. Stabilizing and positive directional selection on the proportion of foragers appeared to be responsible for the evolutionary maintenance of cooperative breeding in this species. Cheaters that reproduce but never forage will be eliminated by colony-level selection. Overall, directional selection favored smaller colony size. Colony-level adaptation is important. because the mode of colony foundation. fission, is likely to enhance additive genetic variance of colonies and create the opportunity for a genetic response to colony-level selection.