Evolutionary ecology of plant defences against herbivores

P>1. Herbivores consume a large portion of the biomass produced by plants in virtually all ecosystems, which has dramatic effects on both the ecology and evolution of plants. In response to this threat, plants have evolved a diverse arsenal of direct and indirect defences to reduce herbivory and the impacts of damage on plant performance. 2. This special feature is a broad synthesis of the evolution and ecology of plant defences. The first objective of this special feature is to provide a review of what we have learned about plant defences against herbivores. The second objective is to stimulate debate and sow fresh ideas for the future research. 3. The 11 articles in this issue address three fundamental questions: (i) How do plants defend themselves against a diverse array of enemies? (ii) Why do plant species vary in defence? And (iii) What are the ecological and ecosystem-level consequences of plant defence? In addressing these questions the articles cover the interdisciplinary nature of plant-herbivore evolutionary ecology, from genes to global patterns. 4. The articles contained in the special feature question existing paradigms and provide new analyses of data. In some cases, influential hypotheses are firmly supported with new analyses (e.g. the Resource Availability Hypothesis), whereas in other instances conventional wisdom is called into question (e.g. the importance of secondary metabolites in the microevolution of resistance) and popular hypotheses are rejected (e.g. the Apparency Hypothesis, the Latitudinal Biotic Interaction Hypothesis). 5. This is an exciting time for research on the evolutionary ecology of plant defences. The articles in this special feature provide a guide to how we can move forward in resolving existing problems and tackling new questions.