Discrimination of conspecifics from heterospecifics in a hybrid zone: behavioural and chemical cues in ants
Résumé
Species and nestmate recognition in social insects occurs mostly through cutic-ular hydrocarbons acting as chemical cues. These compounds generate a colony-specificodor profile depending on genetic and environmental factors. Species and nestmate recog-nition results in specific behavioral responses, regulating the level of aggression towardother individuals during an interaction. Although species discrimination and recognitioncues have been poorly studied in the context of interspecific hybridization, such systemsoffer an opportunity to further investigate the influence of heritable and environmental fac-tors on recognition. We explored the strength of discrimination in a hybrid zone betweentwo ant species—Tetramorium immigransandT. caespitum—by comparing cuticular hy-drocarbon profiles and measuring intra- and interspecific worker aggression in both areasof sympatry and areas of allopatry among species. Species cuticular hydrocarbon profileswere well-differentiated and interspecific aggression was high, revealing highly discrim-inating species recognition cues. Hybrids’ cuticular hydrocarbon profiles consisted of amixture of the parental bouquets, but also exhibited hybrid-specific patterns. Behavioralassays showed thatT. immigransis as aggressive toward hybrids as toward heterospecifics.Finally, aggression between heterospecific workers was lower when interacting individu-als came from areas of sympatry among species than from areas of allopatry. Taken as awhole, these findings paint a particularly complex picture of the recognition system inT.immigrans,T. caespitum, and their hybrids, and highlight that hybrid zones afford a stillunderexplored opportunity for investigating recognition mechanisms and discriminationbetween species
