Contribute to evolutionary theory by clarifying the role of the physical environment as a motor of evolution Examine the interplay between habitat fragmentation and faunal turnover rates to understand the effects of global change Decipher the time scale at which environmental changes are most likely to affect evolution of terrestrial mammalian faunas Hypothesis 1. Tectonism itself acts to increase taxonomic richness. Hypothesis 2. Long-scale climatic change increases taxonomic richness more than tectonic change does. Hypothesis 3. Long-scale climate change increases taxonomic richness more than cyclical, short-scale climate change. Hypothesis 4. Short-scale climate change increases taxonomic richness more than long-scale tectonic change. Hypothesis 5. High-frequency, high-magnitude climatic events (like Pleistocene climate changes) substantially alter the pre-existing faunal baseline. Hypotheses 1-4 are designed to untangle the relative importance of various kinds of physical-environmental perturbations on taxonomic richness. Hypothesis 5 sets off in a slightly different direction by examining whether high-magnitude, high-frequency physical-environmental disruptions (Pleistocene climate change) are enough to override the basic taxonomic legacy that was put in place during earlier Cenozoic events.