PARENT SESSION
Oral Session # 53: Herbivory IV: Communities, Populations, and Genetics.
Presiding: JA Rudgers
Wednesday, August 6. 1:30 PM to 5:00 PM, SITCC Meeting Room 103.

Population dynamics in a heterogeneous environment: Herbivore population response to variance in plant quality.

Underwood, Nora^*,1, ¹ Florida State University, Tallahassee, FL

ABSTRACT- The quality of individual plants and mean quality of plant populations can influence herbivore populations, but little is known about the effects of variance in plant quality. Using field experiments with wild strawberry (Fragaria chiloensis) and strawberry aphid (Chaetosiphon fragaefollii) I examined how variance in plant quality affected aphid population dynamics. I identified plant genotypes with differing effects on aphid population dynamics, and constructed plant populations that were monocultures of individual genotypes or mixtures of the genotypes used in the monocultures. I followed aphid population dynamics on each of these plant population types in the field and fit population dynamic models to the resulting time series. These data allow me to ask how dynamics on individual plant genotypes in the monocultures relate to dynamics in herbivore populations on mixtures of plants. Results suggest that the variance in quality among plant genotypes affects aphid population dynamics. Estimated aphid population growth rates and carrying capacities on mixtures of plant genotypes are often not the average of those parameters on monocultures of the genotypes included in the mixture. Depending on the particular genotypes included in the mixtures, aphid population sizes can be either higher or lower than the expected population size based on the average of the monocultures. Aphid movement among plants within a population appears to be an important mediator of the effects of variance in plant quality on aphid populations.

Key words: plant-insect interactions, population dynamics, variance