Understanding the processes that control speciation is critical to any modern macroevolutionary synthesis. A variety of theoretical constructs have been proposed to explain various differential speciation patterns observed in the fossil record, such as higher rates of speciation among stenotopic vs. eurytopic species. Most of these explanations, however, rely on only one or two explanatory variables and may be overly simplistic. Developing a more complete understanding of speciation processes requires a broader synthesis of multiple explanatory factors including the role of external factors such as climate and plate tectonics, impact of ecosystem-level processes, relative niche breadth and relative stability of species’ niches during environmental change (biotic and abiotic). This study explores the relationship between biogeography, ecological niches and speciation in a series of case studies focusing on the Late Ordovician and Late Devonian shallow marine brachiopods and bivalves and Neogene horses of North America.