Workers determine queen inheritance of reproduction in a functionally monogynous ant population

In cooperatively breeding animals there is potential for conflict among group members over reproductive sharing (skew). The outcome of such conflict depends on which individuals have power. Theoretical treatments of skew generally assume that power rests with those directly reproducing, but in eusocial insects, an important group for testing skew theory, nonreproductive workers are known to be influential in other colony conflicts such as sex ratio. We investigated the role of queens and workers in determining queen inheritance of a newly vacant reproductive position in a functionally monogynous (only one queen reproduces) population of the ant Leptothorax acervorum. Multiple-queen colonies with an already established reproductive queen were split in half producing a fragment containing multiple, previously nonreproductive queens. Loss of the established queen simulates a queen turnover event as occurs in nature. We found that worker behaviour influenced which queen filled the vacant reproductive position, with this queen receiving on average less aggression and more grooming from workers than the other queens. This study shows that after loss of the established queen, workers can modify their behaviour towards individual queens, and, contrary to skew models, skew among queens remains high despite changes in relatedness asymmetry. Our results suggest workers collectively hold considerable power over skew among queens.