Plant-carnivore interactions: evolutionary and ecological consequences forplant, herbivore and carnivore

Many terrestrial food webs are dominated by direct and indirect interaction s among higher plants and arthropods. Direct interactions occur between a c onsumer and its food. Indirect interactions do not involve consumption. The y may occur when plants promote the effectiveness of carnivorous arthropods by emitting herbivore-induced volatiles in response to herbivory. These vo latiles are an important solution to a foraging problem of carnivorous enem ies. The volatiles are emitted in large amounts and the blend composition c an be specific for the plant species, plant genotype or for the herbivore s pecies or instar damaging the plant. The characteristics of the chemical in formation such as the degree of specificity and thus the information value for the responding insects differ largely among plant species. After their emission, the induced plant volatiles may also affect herbivores, other pla nts, or competitors or predators of the carnivores. Thus, an information we b is superimposed upon the food web. This information web is more complex t han the food web itself. The information-mediated interactions that result from the emission of herbivore-induced plant volatiles have consequences fo r the ecology and evolution of plants, herbivores and carnivores in a food web. For instance, other plants, neighbouring the signalling plants, may pr ofit from the attracted carnivores, which may influence the strategy of the signaller. Herbivores may exploit the information in selecting food plants to avoid competition or enemy-rich space and carnivores may use the inform ation in developing a flexible foraging strategy with maximal reproductive success, e.g. through associative learning of the cues. In this chapter we compare different simple multitrophic systems with the a im of reaching generalities with regards to the ecological and evolutionary consequences of the most important information flows.