Herbivore offense in plant-herbivore coevolution.

Coevolution between plants and herbivores has been proposed as a major evolutionary force that resulted in their radiation and diversification. Plants have evolved a broad array of strategies that directly or indirectly avoid, repel, deter, or kill herbivore attackers. These include (but not limited to) tolerance to damage through compensatory growth of tissue lost from herbivory, resistance via physical and chemical defenses, induced responses, and avoidance through reduced apparency or phenological mismatch. In response, herbivores have evolved adaptations to circumvent, resist, detoxify and even use plant defenses for their own benefit (e.g., sequestration). These include anatomical, physiological and behavioral adaptations, but also symbiotic associations to overcome the defenses of the host plant. Ecologists and evolutionary biologists have been studying plant-herbivore interactions for decades. Recent advances in community ecology, genomics, metabolomics and transgenic approaches allowed us to uncover the mechanisms by which some herbivores acquired the ability to neutralize plant defenses, or how plant communities reduce herbivory by creating heterogeneous chemical landscapes. Future research should consider integrating trait syndromes rather than individual traits when testing hypotheses about plant-insect coevolution, and including the third trophic level as an important selective force in plant-herbivore coevolution.