Ecological and Evolutionary Constraints to Herbivore Resistance in a Native Plant-Multiple Herbivore CommunityEPA Grant Number: U915654
Title: Ecological and Evolutionary Constraints to Herbivore Resistance in a Native Plant-Multiple Herbivore Community
Investigators: Wise, Michael J.
Institution: Duke University
EPA Project Officer: Manty, Dale
Project Period: August 1, 1999 through August 1, 2002
Project Amount: $86,234
RFA: STAR Graduate Fellowships (1999) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Ecology and Ecosystems
The objective of this research project is to identify constraints on the evolution of resistance to herbivory in natural plant populations. Specifically, the focus is on investigating whether a consideration of an entire community of herbivores will illuminate potential constraints that would not be apparent from the traditional concentration on just one focal herbivore species.
This research project focuses on the native herbaceous weed horsenettle (Solanum carolinense, Solanaceae) and its community of insect herbivores. Four populations of horsenettle have been observed to characterize differences in the composition of the herbivore communities. In 1997, roots of 30 genetic individuals (genets) were collected from each population, and clones propagated from these individuals will serve as the subjects of controlled experiments investigating constraints on the evolution of resistance. In the summer of 2000, a field experiment will be performed to determine the separate and combined effects of floral and foliar herbivores on plant fitness. Non-additivity of fitness impact by these two types of herbivores may alter the pattern of selection on resistance in such a way that increased resistance is not favored. An additional field study will investigate competitive interactions among herbivores in this community that may interfere with potential selection acting on genetic variation for resistance to given herbivores. In the summer of 2001, a large field experiment will be performed in which approximately 15 clonal individuals from 44 genets will be randomly transplanted into an old field. Herbivory and fitness measurements will be taken on the plants until the end of the growing season. Genetic variation for resistance to each species and covariance for resistance among species will be calculated. Regression techniques will be used to characterize the natural selection (if any) acting on resistance in the experimental population.
This research project will reveal that novel constraints on resistance emerge with a consideration of more than one herbivore species. These constraints include genetic correlations in resistance to different herbivores, ecological interactions among the herbivores, non-additivity of the combined impact of multiple herbivores, and spatial/temporal variation in herbivore community structure.