9423424 VESSEY A central question in ecology is: what factors affect population size? Most previous models incorporated only density-dependent factors because density-independent factors are difficult to analyze statistically and manipulate experimentally. However, because real environments vary, population models should include stochastic environmental factors to describe population dynamics accurately. The objectives of this study are to explain and predict population fluctuations based on stochastic environmental conditions, using statistical techniques previously unused in an ecological context. The effect of weather on Peromyscus densities in one- and two-species communities will be modeled using data sets of twenty and fifteen years, respectively. Population densities will be forecasted, and simulations will determine the effect of different weather regimes on densities. Inclusion of stochastic weather in population models will lead to better explanation and forecasting of population fluctuations.
