Chemical Recognition Cues in Ant-Aphid Mutualism: Differentiating, Sharing, and Modifying Cuticular Components

Aphid-tending ants form mutualistic associations with aphids. During their interactions, aphids and ants use both tactile stimuli and chemical cues to communicate. Recent studies suggest that ants modify the cuticular hydrocarbons of mutualistic aphids they attend, but it is unclear which compounds are implicated in recognition. Thus, we investigated the chemical basis for the discrimination between attended and unattended aphids, Aphis gossypii Glover (Hemiptera: Aphididae), by the ant Tapinoma ibericum (Santschi, 1925) including cuticular hydrocarbons (CHCs and non-CHCs) compounds in the analysis. Chemical profiles of 14 colonies of A. gossypii attended by ants for three days were significantly different from those of unattended aphids. These results show that contact with T. ibericum rapidly induces modification of the cuticular profiles of the aphids on which they feed. Moreover, the compounds of unattended aphid A. gossypii also change over time but differ from those of attended aphids. The main compound of the ant cuticle (3,15-di-MeC27), which is highly abundant in attended aphids, was identified as a possible recognition marker, but without forgetting other identified compounds that may also play a predominant role in the ant-aphid mutualistic interactions. These promising compounds represent opportunities for pest control strategies using chemical manipulations.