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2 - Recruitment of predators and parasitoids by herbivore-injured plants
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- By Ted C. J. Turlings, Institute of Zoology, University of Neuchatel, Switzerland, Felix Wäckers, Netherlands Institute of Ecology, Heteren, the Netherlands
- Edited by Ring T. Cardé, University of California, Riverside, Jocelyn G. Millar, University of California, Riverside
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- Book:
- Advances in Insect Chemical Ecology
- Published online:
- 07 August 2009
- Print publication:
- 21 June 2004, pp 21-75
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Summary
Introduction
In recent years, induced plant defenses have received widespread attention from biologists in a variety of disciplines. The mechanisms underlying these defenses and the interactions that mediate them appeal not only to plant physiologists, ecologists, and evolutionary biologists but also to those scientists that search for novel strategies in plant protection. Several recent books (Karban and Baldwin, 1997; Agrawal et al., 1999) and reviews (Baldwin, 1994; Karban et al., 1997; Agrawal and Rutter, 1998; Agrawal and Karban, 1999; Baldwin and Preston, 1999; Dicke et al., 2003) have been devoted entirely to the subject of induced plant defenses. Various forces, ranging from abiotic stresses to biotic factors such as pathogens, arthropods, or higher organisms, may trigger different plant defense responses. Yet, the biochemical pathways that are involved appear to show considerable similarities. This is also true for the so-called indirect defenses.
The term indirect defense refers to those adaptations that result in the recruitment and sustenance of organisms that protect the plants against herbivorous attackers. The early published examples of indirect defenses involved intimate plant–ant interactions, in which myrmecophilous plants were shown to have evolved a range of adaptations providing ants with shelter (domatia) and various food sources (Belt, 1874; Janzen, 1966). In return, these plants may obtain a range of benefits because ants can provide nutrition (Thomson, 1981) or more commonly, protection against herbivores, pathogens, and competing plants (e.g. Koptur, 1992; Oliveira, 1997).
7 - The chemical ecology of plant–caterpillar–parasitoid interactions
- Edited by Teja Tscharntke, Georg-August-Universität, Göttingen, Germany, Bradford A. Hawkins, University of California, Irvine
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- Book:
- Multitrophic Level Interactions
- Published online:
- 08 August 2009
- Print publication:
- 21 March 2002, pp 148-173
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Summary
Introduction
Predators and parasitoids can be major mortality factors for many herbivorous insects. As such, these members of the third trophic level may positively affect the fitness of certain plants on which the herbivores feed. Such indirect ecological links between the third and first trophic level appear to have resulted in some spectacular adaptations in plants, as well as in the natural enemies. Most evident are the morphological adaptations that result in a very close relationship between certain plants (e.g., Cecropia and Acacia) and ants that use these plants as their home and major source of food. These plants may carry structures that allow them to harbor (in hollow thorns or roots) and feed (with extrafloral nectar organs or food bodies) ants. While the ants benefit from lodging and food, the plants benefit from protection against herbivores. It is generally accepted that the plant structures and secretions secure the protection by ants (e.g., Janzen, 1966; McKey, 1988; Oliveira, 1997).
A less obvious plant adaptation are the signals that plants emit when they are damaged by herbivores. These signals, which are emitted in the form of volatile substances, are used by predators and parasitoids to locate potential prey or hosts. Although there are several alternative possible functions for these emissions, evidence for their role in the attraction of the third trophic level is accumulating. This chapter selectively reviews and discusses this evidence.