Folivory Affects Composition of Nectar, Floral Odor and Modifies Pollinator Behavior
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Herbivory induces changes in plants that influence the associated insect community. The present study addresses the potential trade-off between plant phytochemical responses to insect herbivory and interactions with pollinators. We used a multidisciplinary approach and have combined field and greenhouse experiments to investigate effects of herbivory in plant volatile emission, nectar production, and pollinator behavior, when Pieris brassicae caterpillars were allowed to feed only on the leaves of Brassica nigra plants. Interestingly, volatile emission by flowers changed upon feeding by herbivores on the leaves, whereas, remarkably, volatile emission by leaves did not significantly differ between infested and non-infested flowering plants. The frequency of flower visits by pollinators was generally not influenced by herbivory, but the duration of visits by honeybees and butterflies was negatively affected by herbivore damage to leaves. Shorter duration of pollinator visits could be beneficial for a plant, because it sustains pollen transfer between flowers while reducing nectar consumption per visit. Thus, no trade-off between herbivore-induced plant responses and pollination was evident. The effects of herbivore-induced plant responses on pollinator behavior underpin the importance of including ecological factors, such as herbivore infestation, in studies of the ecology of plant pollination.
KeywordsBrassica nigra (black mustard) Flower visitors Herbivore-induced plant volatiles Herbivory Honeybees Syrphid flies
We thank Ciska Raaijmakers for helping with the glucosinolate and sugar analyses, Johan Calis and Willem-Jan Boot for the supply of the honey bees, André Gidding, Leo Koopman, Frans van Aggelen for rearing cabbage whites, and Bert Essenstam and Unifarm for growing mustard plants and field maintenance.
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