Visual and odour cues: plant responses to pollination and herbivory affect the behaviour of flower visitors

1. Plants evolved strategies to attract pollinators that are essential for reproduction. However, plant defence against herbivores may trade off with pollinator attraction. 2. Here, we investigated the role of inducible plant secondary metabolites in such a trade-off. Our objective was to reveal the mechanisms underlying the effects of induced plant responses to pollination and herbivory. We assessed how responses of plants to pollination and insect herbivory affect the behaviour of flower visitors. Subsequently, we investigated how the production of volatile and non-volatile compounds changes after pollination and herbivory. 3. Both herbivores and pollinators induced important phenotypic changes in flowers. Brassica nigra plants respond to pollination and herbivory with changes in the profile of volatiles and non-volatiles of their flowers. Our results show that butterflies use different cues when searching for an oviposition site or a nectar source. Pollination status influenced the behaviour of butterflies, but not that of syrphid flies. 4. We discuss the results in the context of the trade-off between defence and reproduction in plants and suggest that systemic responses to herbivores can interfere with local responses to pollination. Therefore, these responses must be addressed in an integrated way because, in nature, plants are simultaneously exposed to herbivores and pollinators.