Many theories and hypotheses have been proposed to explain patterns of species diversity and distribution/abundance at particular scales, but they are often unclear on how these ideas relate or how they apply across multiple scales. It has been difficult to use diversity theory to understand patterns at the intermediate scales at which biodiversity is managed. Here, we present a framework for studying diversity based on the ecological processes influencing distribution of organisms at different scales. We use this framework to organize diversity theories into several classes. The framework highlights that processes contributing to diversity patterns depend on the characteristics of the taxa considered, the spatial scales at which organisms respond to environment, and the scales and other characteristics of the particular environments in which investigators hope to explain variation in diversity. At the scales traditionally considered by land managers and conservation biologists, biodiversity is determined b the interactions among habitat occupancy, landscape distribution, and geographic range for a variety of taxa. The framework suggests that, in each case, managers should address the following general questions: 1) which groups of organisms will be considered, 2) how do their domains of scale relate to the land area under consideration, 3) what processes are likely to be important determinants of species distribution at management scales, and 4) how will the proposed management activities interact with these processes? We emphasize the value of considering species diversity theories in a pluralistic and case-specific way, rather than seeking singular explanations or "general laws" explaining diversity variations.