Empirical and theoretical studies have implicated habitat coarseness and co-evolution as factors in driving the degree of specialization of mutualists and pathogens. We review recent advances in the development of a framework for host-symbiont interactions that considers both local and stochastic interactions in a spatially explicit habitat. These kinds of interactions result in models with large numbers of parameters due to the large number of potential interactions, making complete analysis difficult. Rigorous analysis of special cases is possible. We also point to the importance of combining experimental and theoretical studies to identify relevant parameter combinations.