How habitat edges change species interactions

Traditionally, ecologists interested in habitat edges have focused on edge- related gradients in patterns of species richness or abiotic variables. Her e, however, we take a different perspective, attempting to synthesize recen t empirical results concerning the effects of habitat edges on population d ynamics with contemporary theoretical developments to outline the ways in w hich species interactions, and the dynamics of the communities in which the y are embedded, can be changed by habitat edges. We find a striking converg ence between empirical notions of a patch's core area and analytical result s from partial differential equation models. A review of both empirical and theoretical studies suggests four general classes of mechanisms through wh ich habitat edges can have similar impacts on dissimilar types of species i nteractions. Specifically, we focus on edges' roles as dispersal barriers o r filters, edges' influences on mortality, edges' involvement in spatial su bsidies (in which dispersers' intrapatch impacts are maintained by their ac tivities in other habitats), and edges' roles as generators of novel intera ctions. For each class of edge-mediated effects, we provide examples of how one can use spatial modeling to address the relevant questions on these to pics, which together form a key link between community dynamics and landsca pe structure.