Kin discrimination increases with odor distance in the German cockroach

Abstract

Kin recognition mediates altruistic behavior and inbreeding avoidance in many animal societies. So far, evidence for accurate kin recognition, when individuals distinguish fine scale differences in genetic relatedness, in social insects is mixed. Although this ability should be counter selected to reduce risks of nepotism in eusocial colonies, accurate kin recognition may be beneficial in less integrated societies where genetic conflicts are reduced. Here we show that gregarious cockroaches Blattella germanica discriminate multiple levels of relatedness and identify inherited cuticular odors as potential kin recognition cues. When given a choice between aggregation sites containing either full siblings or less related conspecifics, cockroaches showed an increasing preference for resting with full siblings with increasing genetic distance between stimuli groups, from 50% of choices in the presence of half siblings or cousins, to 60.7% with less related cockroaches from the same strain, and 72.9% with cockroaches from a different strain. Examination of the cuticular hydrocarbon profiles of 288 nymphs and their 54 parents revealed that the chemical distance between cockroaches was negatively correlated to their relatedness. Using a Bayesian animal model approach for quantitative genetic analyses, we identified several highly heritable methyl-branched alkanes as good candidates for kin recognition cues. Our results suggest that kin recognition is based on genetically inherited odors in this gregarious insect and highlight mechanistic similarities with nestmate recognition in eusocial species.