Population Dynamics in a Heterogenous Environment: The Effect of Variance in Plant Quality on Herbivore Populations in Time and Space

Florida State University, Tallahassee FL

Investigators

Abstract

0089570. Nora Underwood. Considerable ecological research has documented the way in which herbivores respond to mean characteristics of their food; however, little is known about the way in which variability in food quality affects individual herbivores or populations of herbivores. The proposed research will quantify the way in which variance in quality among plants affects the movement of individuals, as well as the population dynamics of insect herbivores. A spatially explicit model will be used to examine how herbivore movement influences the interaction between the variance in plant quality and population dynamics in time and space. This model will then provide a framework for understanding how variance in quality among phenotypes, genotypes, or species of plants affects insect demographics. Field experiments will examine how variability in the genetically based quality of strawberry populations affects the movements and population dynamics of the strawberry aphid. Short-term experiments will quantify the way in which the movement of individual aphids is related to population-level variance in forage quality. Longer-term experiments will relate the dynamical response of aphid populations to different kinds of variance in food quality, ranging from that characteristic of plant monocultures to that characteristic of mixed cultures of two to six different genotypes. This approach will facilitate a critical examination of the hypothesis that agricultural mixtures of plant varieties (genotypes) support lower population densities of pests than will monocultures. Finally, linking the genetic variance in plant quality to the demographics of herbivores provides a critical synthesis of ecological and evolutionary perspectives in understanding plant-herbivore dynamics.