Collaborative Research: A Role for Insect Herbivores in Plant Population Growth and Regulation: Density Manipulations and Demographic Models

Pacific University, Forest Grove OR

Investigators

Abstract

Knowing the factors that control plant population size is important for our basic understanding of nature and for developing methods for controlling weedy and invasive plants. Ecologists agree that plants are often limited by competition with other plant species for resources. However there is debate about how important insects that eat plants (herbivores) are in controlling plant populations. Previous tests of the influence of herbivores have considered only effects on plant reproduction under low-density conditions and have not accounted for how the influence of herbivores changes with plant density. This study will use field experiments coupled with mathematical models to determine the influence of insect herbivores on the population growth of a weedy plant over a range of plant densities. Invasive and weedy plants impose enormous economic and environmental costs in the USA. Much attention has focused on using bio-control agents, particularly insect herbivores, to control these plants. This approach assumes that herbivores strongly affect plant populations. This project will provide the most complete test of this assumption to date. It will also help train new scientists, involving students as assistants (learning research techniques, data analysis and computer programming), and as independent researchers (learning to design studies, and present results).