Population stability in animal

This dissertation contains five sections. Section I is an introduction.

Section II of this dissertation has been published in the book entitled "Insect Outbreaks" edited by P. Barbosa and J.C. Schultz (Redfearn and Pimm 1987) . Section III has appeared in "Ecological Monographs" (Redfearn and Pimm 1988) . Section IV will be published in an Oak Ridge National Laboratory Technical Memorandum entitled "Recent Advances in Food Web Theory" edited by D.L. DeAngelis (Redfearn and Pimm, in press). Section V will appear in "Nature" (Pimm and Redfearn, in press).

In section II I show that the application of insecticidal sprays causes an increase in the rate of population growth of certain insect pests.

In section III I report that variability in population density through time may be lower in herbivorous insect species that feed on a wide range of host plants than in species with a narrower diet. Other authors have reported the opposite result.

Section IV also examines temporal population variability. This section reviews the literature on temporal population variability. I recognize three kinds of factors that may affect variability: environmental factors, community effects, and the intrinsic properties of the species. I show that body size is negatively correlated with variability.

In section V I report that estimates of temporal population variability increase as we include more years of data in those estimates. This is consistent with the idea that time series of population densities have reddened spectra: high amplitude fluctuations in density occur less frequently than low amplitude fluctuations. Major changes in numbers are rarer than minor changes.