The effects of drought on plant–pollinator interactions: What to expect?

Current predictions suggest that in temperate zones climate change will increase the frequency of extreme events such as summer droughts, leading to deficit in water availability for ecosystems. Plants will more often experience water stress during the spring and summer. The effects of drought on plants in these systems have predominantly been studied in wind-pollinated crop species, focusing on vegetative growth or yield. Although a majority of flowering plants (87 % of all angiosperms) is insect-pollinated, the effects of drought on plant–pollinator interactions are not well studied. However, plant pollination and reproduction phases are highly sensitive to this abiotic stress. At plant individual scale, we hypothesize that drought will alter plant–pollinator interactions via (i) signals or cues for insect visitors (floral display, plant height, number of flowers per plant, flower color, shape and size, olfactory compound quantity and composition) and (ii) floral rewards (nectar volume, total sugar concentration, sugar composition, pollen quantity and chemical composition). In this review, we synthesize evidence related to the effects of drought on floral signals and rewards, and discuss how they may disrupt plant–pollinator relationships