Ecology, 81(7), 2000, pp. 18041813
2000 by the Ecological Society of America
BENEFITS AND COSTS OF INDUCED PLANT DEFENSE FOR
LEPIDIUM VIRGINICUM (BRASSICACEAE)
ANURAG A. AGRAWAL1
Department of Botany, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada M5S 3B2.
Abstract. Induced responses to herbivores are common and well documented in plants.
It has been hypothesized that the evolutionary ecology of induced responses can be un-
derstood by studying benefits of induction in the presence of herbivores and costs of
induction in the absence of herbivores. Phenotypic benefits and costs of induction would
indicate that such plasticity in defense could be adaptive (i.e., that phenotypes matched to
their environmental conditions have higher relative fitness than unmatched phenotypes).
However, few studies to date have investigated the benefits and costs of induction in the
same system. In this study, induced responses of Lepidium virginicum to herbivory reduced
feeding by generalist noctuid caterpillars in choice and no-choice experiments. Induced
plant responses to herbivory were correlated with an increase in the number of trichomes
per leaf and an increase in the diversity of the putatively defensive chemical compounds,
glucosinolates, present in the foliage of damaged plants compared to undamaged controls.
Induction did not affect the feeding behavior of the larvae of the specialist butterfly, Pieris