Charles Davis' research on plant diversity integrates the disciplines of systematics, paleobiology, evolution, ecology, and molecular biology. One major theme that unites these disciplines is phylogenetic theory, which he applies to reconstruct the history of plant diversity through evolutionary time. Biogeography, biome evolution, plant-insect interactions, and horizontal gene transfer are some of the focal points of his work in this area. His recent projects have sought to understand the origins of intercontinental disjunctions, the age of modern tropical rain forest, the maintenance of morphological stasis in the tree of life, and mechanisms for horizontal gene transfer. This research combines fieldwork with specimen-based studies in the herbarium and molecular approaches in the lab. Broader interests of his lab also include monographic and floristic study.