A main goal of comparative phylogeography is to examine the evolutionary history of multiple species in order to determine the processes that have driven patterns of speciation and biodiversity across a landscape. We combine ecological niche modeling, and ecological experimentation to address the mechanisms driving range distributions of lineages and species. We emphasize a quantitative approach to phylogeography (e.g., Lapointe and Rissler 2005, American Naturalist), and much of our work focuses on California and the southern Appalachians.