Today and tomorrow: impact of climate change on aphid biology and potential consequences on their mutualism with ants

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.