Date of Award:

5-2004

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Biology

Committee Chair(s)

Edward W. Evans

Committee

Edward W. Evans

Committee

James W. Haefner

Committee

William P. Kemp

Committee

James Powell

Committee

Joseph Koebbe

Abstract

I explored changes in predator-prey system stability with the addition of spatial heterogeneity in prey density dependent mortality. The results indicated that this addition led to greater stability for all prey spatial distributions if prey was aggregated or loosely aggregated. These results indicated prey spatial distribution was critical to population stability. I next explored whether predator emigration under the above conditions would lead to a host shift. I used Chesson and Murdoch's templates of host density independent (HDI) aggregation and host density dependent (HDD) aggregation in predators as the basis for my metapopulation models. I varied prey density dependent mortality levels, prey spatial distribution, and predator efficiency to explore predator host shifts. Initial prey and predator spatial parameters were used from the unstable regions of the single population model to test the premise that predator outbreaks led to host shifts. The results in both the HDI and HDD models showed that prey density dependent mortality levels, prey spatial distribution, and predator efficiency were all important factors leading to host shifts. Complete host shift was observed in one case in the HDI metapopulation model and in multiple cases in the HDD metapopulation model. These results are important from both a biocontrol as well as an evolutionary perspective in understanding how spatial scales and levels of prey population density are critical in establishment of host shifts.

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