Plant-herbivore interactions: Thinking beyond larval growth and mortality

Abstract

Plants provide food and habitat for numerous species of the animal kingdom. The multitude of resources that they provide is commonly thought to be one of the main reasons behind the remarkable adaptive radiation of terrestrial animals (Herrera, 2002). Because of their small size and specific feeding requirements, insect herbivores usually have a lifelong and more intimate association with their host plants than vertebrate herbivores (Strauss and Zangerl, 2002). Insect herbivores typically cause harm to plants by feeding on vegetative tissues, roots, fluids, flowers, or seeds, thus reducing the plants’ fitness (Kareiva, 1999; Strauss and Zangerl, 2002). To limit herbivore damage, plants produce numerous antiherbivore chemicals that function as toxins, feeding deterrents, or antidigestive compounds (Chen, 2008). Ingestion of such chemicals causes phenotypic changes in the insects because they must expend valuable nutrient resources to neutralize and/or reduce the harmful effects from these compounds (Agrawal, 2001; Chen, 2008). Moreover, changes to insect behavior, morphology, physiological processes, or biochemical pathways, resulting from resource investment trade-offs, can also affect different insect performance traits associated with these systems (Saha et al., 2012).