A mathematical model is developed for the dynamics of seed-dispersed tree species in a region of forest patches or islands. The relevant variables are the population numbers of individual species populations on each patch. A model that considers only one tree species (of the many present) in a region of N distinct patches is formally analogous to a model of an N-species mutualistic community. Using the theory of M-matrices, which has been successfully applied to mutualistic communities, criteria for persistence and stability of the species are derived. The model is then extended to a community of L species that interact competitively and mutualistically in an N-island region. The possibilities of obtaining numerical parameters for the models are discussed. © 1979.