A method for detecting kin discrimination within natural colonies of social insects

If social insect workers can distinguish degrees of relatedness among their colonymates, then they are expected to favour their closest relatives rather than acting purely for the good of the colony. Wivhin-colony kin discrimination therefore occupies a central position in attempts to understand the balance of cooperation and conflict in social insects, but the existence of such within-colony discrimination in nature remains controversial. Most attempts to study within-colony discrimination have employed unnatural manipulations to allow the investigator to assess mainline or patriline membership. Here, a method is described that does not require explicit identification of matrilines or patrilines, so that the unnatural manipulations can be avoided. Instead, this method uses genetic markers to obtain statistical estimates of relatedness differences. The tests are made powerful through use of paired comparisons that eliminate the between-colony variance. This is demonstrated with both real and simulated examples. It is noted that the social insects themselves might use related methods to improve the accuracy of within-colony discrimination.