The importance of natural enemies of herbivores as agents of selection for plant genotypes within species

EPA Grant Number: U915372
Title: The importance of natural enemies of herbivores as agents of selection for plant genotypes within species
Investigators: Rudgers, Jennifer A.
Institution: University of California - Davis
EPA Project Officer: Packard, Benjamin H
Project Period: September 28, 1998 through January 1, 2000
Project Amount: $78,694
RFA: STAR Graduate Fellowships (1998) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Ecology and Ecosystems


In natural ecosystems both direct and indirect plant defenses can suppress herbivorous insect damage. Direct plant defenses include traits such as toxic secondary compounds that often decrease herbivore fitness and damage to plants. Indirect plant defenses are generally more subtle. These traits reduce herbivore fitness via an interaction with the enemies of herbivores. A classic example is the extrafloral nectary. In plants such as ant-acacias, extrafloral nectaries attract ants that patrol the leaves and remove herbivores. Indirect plant defenses have largely been neglected in agricultural systems. Crops are bred primarily for direct resistance to herbivores and indirect resistance traits may be lost in certain cultivars. Interactions between host plant traits and the natural enemies of herbivores could be important for pest control. In the process of breeding for direct plant resistance characters, we may be overlooking important plant traits that promote the effectiveness of natural enemies.

I intend to use a wild relative of cotton, Gossypium thurberi (Malvaceae), that is native to the Sonoran desert of North America as a model system for investigating the specific question: Are plant traits shaped by selection from the natural enemies of herbivores? In other words, are certain plant traits favored that allow natural enemies of herbivores to forage more efficiently, thereby reducing damage to the plant? I will focus on two of G. thurberi's major, native insect pests: the cotton leaf perforator, Bucculatrix thurberiella (Lepidoptera: Lyonetiidae), and the cotton boll weevil, Anthonomus grandis (Coleoptera: Curculionidae), and their parasitoids and predators. My hypothesis is that plant traits, such as extrafloral nectaries, that increase foraging by the natural enemies of these herbivores will decrease damage by herbivores and, ultimately, increase plant fitness.

Supplemental Keywords:

RFA, Scientific Discipline, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Southwest, Ecology, exploratory research environmental biology, Environmental Chemistry, Ecosystem/Assessment/Indicators, Chemical Mixtures - Environmental Exposure & Risk, Ecosystem Protection, Ecological Effects - Environmental Exposure & Risk, Ecological Effects - Human Health, Ecology and Ecosystems, Ecological Indicators, Sonoran Desert, natural selection, agents of selection, ecosystem assessment, herbivores, Anthonomus grandis, plant genotypes, plants, cotton boll weevil, ecosystem, natural enemies, direct plant resistance characters, Gossypium thurberi (Malvaceae), cotton leaf perforator

Progress and Final Reports:

  • 1999
  • Final