Testing the potential for conflicting selection on floral chemical traits by pollinators and herbivores: predictions and case study

Abstract

Summary1. There are myriad ways in which pollinators and herbivores can interact via the evolutionary and behavioural responses of their host plants.2. Given that both herbivores and pollinators consume and are dependent upon plant‐derived nutrients and secondary metabolites, and utilize plant signals, plant chemistry should be one of the major factors mediating these interactions.3. Here we build upon a conceptual framework for understanding plant‐mediated interactions of pollinators and herbivores. We focus on plant chemistry, in particular plant volatiles and aim to unify hypotheses for plant defence and pollination. We make predictions for the evolutionary outcomes of these interactions by hypothesizing that conflicting selection pressures from herbivores and pollinators arise from the constraints imposed by plant chemistry.4. We further hypothesize that plants could avoid conflicts between pollinator attraction and herbivore defence through tissue‐specific regulation of pollinator reward chemistry, as well as herbivore‐induced changes in flower chemistry and morphology.5. Finally, we test aspects of our predictions in a case study using a wild tomato species,Solanum peruvianum, to illustrate the diversity of tissue‐specific and herbivore‐induced differences in plant chemistry that could influence herbivore and pollinator behaviour, and plant fitness.