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Recent studies about mutualism consider the complexity and versatility of the relationship, in addition to highlighting the importance of the cost/benefit balance between the two protagonists. Because species interactions are highly dependent on the environment, the climate changes foreseen for the coming years are expected to have significant impacts on the evolution of mutualistic interactions. Among mutualisms, the aphid–ant interaction is well documented, partly explained by the pest status of aphids. This literature review focuses on the impact of climate change (particularly atmospheric carbon dioxide concentration and temperature) on aphid biology and the potential consequences with respect to their mutualistic interactions with ants. We provide an overview of the published reports concerned with the effects of temperature and carbon dioxide on aphids, for which a positive, a negative or no effect has been highlighted. We then discuss how climatic changes can alter four major components of aphid biology that are shaping their interaction with ants: (i) aphid population growth; (ii) aphid behaviour and mobility; (iii) honeydew production and composition; and (iv) semiochemistry. Finaly, we discuss the limitations of such studies on aphid–ant mutualism, as well as the information that is still needed to predict how climate change might impact this type of relationship.

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Honeydew is considered a cornerstone of the interactions between aphids and their natural enemies. Bacteria activity occurring in aphid honeydew typically results in the release of volatile organic compounds (VOCs) that are used by the natural enemies of aphids to locate their prey. Because atmospheric carbon dioxide (CO2) concentration directly impacts the physiology of plants, we raise the hypothesis that elevated CO2 concentrations impact the quantity of honeydew produced by aphids, as well as the diversity and quantity of honeydew VOCs, leading to cascade effects on the foraging behavior of aphids’ natural enemies. Using solid-phase microextraction, we analyzed the VOCs emitted by honeydew from pea aphids (Acyrthosiphon pisum Harris) reared under 450 ± 50 ppm of CO2 (aCO2) or 800 ± 50 ppm CO2 (eCO2). While the total amount of honeydew excreted was only slightly reduced by eCO2 concentrations, we detected qualitative and quantitative differences in the semiochemistry of aphid honeydew between CO2 conditions. Three VOCs were not found in the honeydew of eCO2 aphids: 3-methyl-2-buten-1-ol, 2-methyl-1-butanol, and isobutanol. However, no difference was observed in the searching and oviposition behaviors of hoverfly (Episyrphus balteatus (De Geer)) females exposed to plants covered with honeydew originating from the different CO2 conditions. The present work showed the effect of a particular aspect of atmospheric changes, and should be extended to other abiotic parameters, such as temperature.