Hi: If anyone can help me with the following questions, I'll be grateful: 1) What, if any, are the limitations of handling spatial heterogeneity in ecology thru deterministic models such as reaction-diffusion models (for examoles, see S. A. Levin's papers on the subject).? 2) What are some nondeterministic/statistical ways of studying the effects of spatial heterogeneity on populations and dispersals? Thanx Tejas Desai