Stressful times in a climate crisis: how will aphids respond to more frequent drought?

Aphids are a common and widely distributed group of phloem-feeding insects and are abundant components of insect communities in natural and managed ecosystems. It is anticipated that a changing climate will lead to more frequent periods of drought, which will have consequences for the biology and ecology of these ubiquitous species and the foodwebs they support. To date there has been no comprehensive assessment of the literature to determine the extent to which drought negatively affects aphid fitness. For the first time, we qualitatively and quantitatively assess the literature to determine whether drought stress has an overall negative, positive, or null effect on aphid fitness in terms of development, fecundity, survival and abundance. The underlying causes of changes in aphid fitness are assessed by examining measures of plant growth, nutrition, and defence in relation to the predictions of the plant vigour hypothesis. The meta-analysis indicates that aphid fitness is typically reduced under drought stress, and this is mediated by a reduction in plant vigour and an increase in allocation to defence in drought-stressed plants. We discuss the ecological consequences of increased drought frequency for aphid success, plant resistance against aphids, and aphid-trophic interactions in natural and agricultural systems.