Dissertation Research: Genetic Differentiation Among Populations Of Euphydryas Editha

University Of Texas At Austin, Austin TX

Investigators

Abstract

The proposed work is a sequel to a long-term study of the influence of logging on populations of Euphydryas editha butterfly in Sequoia National Forest, California. Prior work showed that logging influenced the evolution of diet in the butterflies. They acquired a novel hostplant in habitat patches that had been logged, but retained their traditional diet in undisturbed patches. Population growth was faster in the disturbed patches, but insects emigrated disproportionately from those patches, partly because they retained a preference for their traditional habitat and hostplant. The proposed work will examine genetic differentiation both within this disturbed system and between this system and other populations of the same species within a distance of 50 km. The investigators will conduct an equivalent study on an unlogged system in Yosemite National Park and environs. These two studies will ask what genetic differentiation naturally existed among populations of this butterfly and how human activities might be affecting it. The work will also examine how much genetic differentiation among populations is associated with the distance between habitats, the nature of the landscape in the intervening terrain, and the adaptations of the insects to particular host plant species. Human intervention in the landscape affects herbivorous insects in dramatic ways. Introduction of exotic plants alters the range of plant species available as food. Ranching and logging techniques also change the relative qualities of existing native plants. For example, in the current study system logging removed the insects' principal hostplant but incidentally provided a novel host by improving the quality (from the insects' perspective) of a native plant species. Changes in the insects' environment influence their patterns of movement among habitats and their likelihoods of successfully reproducing when they do move. These effects on movement will in turn affect the tendency for populations to differ from each other genetically. This genetic differentiation among populations is the focus of the proposed work, which will illuminate both the natural patterns that exist and the influence that human activities are having upon those patterns.