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vol. 164, no. 1 the american naturalist july 2004 Notes and Comments

Summary: vol. 164, no. 1 the american naturalist july 2004
Notes and Comments
Plant Defense and Density Dependence in the Population Growth of Herbivores
Anurag A. Agrawal*
Department of Botany, University of Toronto, 25 Willcocks Street,
Toronto, Ontario M5S 3B2, Canada
Submitted October 31, 2003; Accepted March 2, 2004;
Electronically published June 3, 2004
Online enhancements: appendix, tables.
abstract: Long-standing theory has predicted that plant defensive
and nutritional traits contribute to the population dynamics of insect
herbivores. To examine the role of plant variation in density depen-
dence, I took a comparative approach by conducting density ma-
nipulation experiments with the specialist aphid, Aphis nerii, on 18
species of milkweed (Asclepias spp.). The strength of density depen-
dence varied on the plant species. Variation in plant secondary com-
pounds (cardenolides), trichomes, leaf carbon and nitrogen concen-
trations, and seed mass of the milkweed species predicted the Rmax
of aphid populations, while specific leaf weight, carbon concentra-
tion, latex, water content, and trichome density were significant pre-


Source: Agrawal, Anurag - Department of Ecology and Evolutionary Biology & Entomollogy, Cornell University


Collections: Environmental Sciences and Ecology