Evolution of Feeding Behavior in Insect Herbivores

Abstract

Insect herbivores are extraordinarily diverse and abundant. Approximately a quarter of the diversity of all eukaryote species can be accounted for by insects that feed on tissues of green plants, excluding those that feed on nectar and pollen. Some insect herbivores feed on diverse plant species from unrelated plant families and may be considered food generalists. Many more have restricted diets; they feed only on species within one plant family, on a group of related plants, or even on just one plant species. Most are also restricted to feeding on particular plant parts, such as leaves, roots, or reproductive organs; smaller insects may be restricted to feeding on particular tissues, such as phloem, parenchyma, or developing seeds. Ecologically, the significance of insect herbivores is profound. First, they can dramatically reduce plant fitness, either directly or indirectly (i.e., by reducing plant competitive ability). Second, they support an almost equal number of species of invertebrate predators and parasitoids. Third, they provide a major food source for a large proportion of birds and lizards and for some small mammals. This diversity of insect herbivores reflects a diversity in diet and feeding behavior. The history of insect