Summary: Chapter 3
WHY INDUCED DEFENSES MAY BE FAVORED OVER CONSTITUTIVE
STRATEGIES IN PLANTS
Anurag A. Agrawal1
and Richard Karban1
Department of Entomology and Center for Population Biology, University of California, Davis, CA
Citation: Agrawal, A. A., and R. Karban. 1999. Why induced defenses may be favored over
constitutive strategies in plants, p. 45-61. In: The ecology and evolution of inducible defenses. R.
Tollrian and C. D. Harvell (eds.). Princeton University Press, Princeton.
Although induced resistance has been documented in over 100 species of plants, why plants employ
facultative defense strategies is not well understood. Although it has been widely accepted that
induction may be a means of reducing resource allocations to defense when not needed, this
explanation is not exclusive of a wide array of hypotheses for the advantages of induced defenses.
In an attempt to shift attention away from the "allocation cost" model, here we focus on several
alternative hypotheses for the benefits of induction. Given that most plants interact with multiple
specialist and generalist herbivores, various pathogens, microbes, and mutualists, a host of
constraints on maintaining constantly high levels of resistance arise. The temporal and spatial