Can cuticular lipids provide sufficient information for within–colony nepotism in wasps?

Inclusive fitness theory predicts that members of non–clonal societies will gain by directing altruistic acts towards their closest relatives. Multiple mating by queens and multiple queens creates distinct full–sister groups in many hymenopteran societies within which nepotism might occur. However, the weight of empirical data suggests that nepotism within full–sister groups is absent. It has been suggested that a lack of reliable recognition markers is responsible. In this paper, we investigated whether epicuticular lipids could provide reliable cues for intracolony kin recognition in two species of social wasps, the paper wasp Polistes dominulus and the hornet Vespa crabro. Epicuticular lipids have previously been shown to be central to kin recognition at the nest level, making them excellent candidates for within–nest discrimination. We genotyped individuals using DNA microsatellites and analysed surface chemistry by gas chromatography–mass spectrometry. We find that in both species epicuticular lipids typically could provide enough information to distinguish related nest–mates from unrelated nest–mates, a difference that occurs in colonies with multiple queens. However, in V. crabro, where colonies may be composed by different patrilines, information for discrimination between full sisters and half–sisters is weaker and prone to errors. Our data suggest that epicuticular lipids at best provide reliable information for intracolony nepotistic discrimination in multiple–queen colonies composed of unrelated lines.