Ecology of Biological Invasion - Spatial Spread by Stratified Diffusion

点击翻译按钮获取中文摘要

1. When a species colonizes a new area, it spreads across that area in the form of an invasion wave. The speed of this wave is determined by not only by random movement into adjacent areas, but also by long-distance dispersal. We studied the invasion process by using a stratified diffusion model, in which both the short and long range dispersal are taken into account. Expansion rates are calculated from numerical simulations and compared with those previously obtained from the analytical model. The results suggest that the stratified diffusion model should provide a basic framework for exploring the mechanisms underlying range expansion. Applying models to the invasion of the House Finch, we evaluate the effects of long- and short-distance dispersals on the range expansion, separately.2. We investigated the speed of invasion waves in a simple stochastic cellular automaton model for a single species on a homogeneous landscape. We show that stochasticity can dramatically increase the speed of invasion waves compared to a simple deterministic version of the model. To explain this phenomenon mathematically, we developed several approximations to the stochastic model. These showed that the increased wave speed in the stochastic model is due to the irregularity in the shape of the wave front, which is present in the stochastic but not the deterministic model.