Absence of within-colony kin discrimination in a multiple-queen ant, Leptothorax acervorum

Inclusive fitness theory predicts that, other things equal, individuals within social groups should direct altruistic behaviour towards their most highly related group-mates to maximise indirect fitness benefits. In the social insects, most previous studies have shown that within-colony kin discrimination (nepotism) is absent or weak. However, the number of studies that have investigated within-colony kin discrimination at the level of individual behaviour remains relatively small. We tested for within-colony kin discrimination in the facultatively multiple-queen (polygynous) ant, Leptothorax acervorum. Specifically, we tested whether workers within polygynous colonies treated queens differently as a function of their relatedness to them. Colonies containing two egg-laying queens were filmed to measure the rate at which individually marked workers antennated and groomed or fed each queen. Relatedness between individual queens and workers was calculated from their genotypes at four microsatellite loci. The results showed there were no differences in the rates at which workers antennated or groomed/fed their more related queen and their less related queen. Workers interacted preferentially with their potential mother queen with respect to grooming/feeding but not with respect to antennation. However, because of high queen turnover, the frequency of adult workers with their potential mother queen still present within the colony was relatively low. Overall, therefore, we found no evidence for within-colony kin discrimination in the context of the average worker's treatment of queens in polygynous L. acervorum colonies.