Highl diverse cuticular hydrocarbon profiles but no evidence for aggression towards non-kin in the ambrosia beetle Xyleborinus saxesenii

Animal societies have nestmate-recognition to protect against social cheaters and parasites. In most social insect societies individuals recognize and exclude any non-nestmate. There, the roles of cuticular hydrocarbons as recognition cues are well documented. Some ambrosia beetles live in cooperatively breeding societies, within nests that are almost completely isolated. Their fungus-farming and inbreeding habits within their nest ensure a nearly complete isolation. However, little is known about whether nestmate recognition is present and adaptive in these ambrosia beetle societies. Here we studied the ability for nestmate recognition in the cooperatively breeding ambrosia beetle Xyleborus saxesenii , combining behavioural observations and cuticular hydrocarbon analyses. Laboratory nests of X. saxesenii were exposed to foreign adult females, from the same population, another population and another species and survival as well as behaviours of receivers and the donor individual were observed. We expected that increasing genetic distance would cause increasing distance in chemical profiles and increasing levels of behavioural exclusion and possibly mortality. Chemical profiles were different between populations and appeared as variable as in other highly social insects. However, we did not find any evidence for behavioural exclusion of foreign individuals. These results suggest that cuticular hydrocarbon profiles might be used for communication, but that exclusion of non-nestmates is either absent in X. saxesenii or agonistic encounters are so rare or subtle that they could not be detected by our method . In the first case it may be adaptive for inbreeding ambrosia beetle species to accept non-nestmate to increase genetic diversity within nests.