Review Article

Proximate and ultimate consequences of polyandry in ants (Hymenoptera: Formicidae)

Baer, B.

Abstract: The process of partner choice and mating is of fundamental importance in ants, because queens copulate only during a very short time window early in their lives prior to egg-laying and eusocial life. As a consequence, several key characteristics of a queen's later emerging colony are defined during these short and early mating events. For example, the number of sperm a queen initially stores determines her total fecundity and therefore limits the size and longevity of monogynous ant societies. A key reproductive behaviour of some queens is that they copulate with more than one male, resulting in postcopulatory sexual selection if ejaculates compete against each other for access to the limited sperm storage space in the spermatheca. Furthermore, polyandrous queens could discriminate against unwanted males and their ejaculates, and thereby manipulate paternities in their own interest, for example, to increase worker relatedness. If sperm from more than a single male becomes stored and used, genetic heterogeneity among helpers increases, which has a number of well documented beneficial effects. However, multiple paternity can also generate costs if helping incentive decreases due to lower inclusive fitness returns for workers. Polyandry can also alter conflicts within insect societies, for example over the sex ratios preferred by queens and workers. Here I consolidate our current knowledge of how early decisions of partner choice and mating in polyandrous ants impact the life history of queens and males as well as their influence on the performance and fitness of the later emerging colony.