Reproductive Consequences of primary polygyny in a harvester ant population

Primary polygyny, the cooperation of multiple unrelated queens in a social insect colony, has been recently documented in multiple taxa but is poorly understood as a behavioral phenomenon. The harvester ant Pogonomyrmex californicus has geographically distinct populations dominated by either monogynous (single queen) or polygynous colonies. A crucial period of harvester ant lifecycle occurs during the annual mating flight. Little is known about how cooperative queens divide reproduction or the fecundity costs they suffer when doing so, but this information is vital to understand how this cooperative behavior has evolved and propagated. We examine the consequences of primary polygyny by capturing entire mating flights of monogynous and polygynous P.californicus colonies and comparing the total reproductive output and sex investment. We also use microsatellite markers to analyze per-queen reproductive contribution. Our data indicates a lower per-queen reproductive output as well as a highly male biased sex investment in polygynous colonies, suggesting a considerable fecundity cost to queens that participate in primary polygyny.