The majority of Zimmer's present research projects deal with studies of the pattern and process of molecular evolution in green plants. When she began her postdoctoral work in 1980, she developed nuclear ribosomal genes as a good model for both phylogenetic and evolutionary process studies. In order to understand the patterns elucidated by this work, Zimmer has collaborated with plant systematists and paleobotanists on syntheses of organismal and molecular phylogenies. At the Smithsonian, this work has continued to use ribosomal and chloroplast gene markers for molecular systematic studies of key groups such as the ferns, Asteraceae, Gesneriaceae, several Pacific genera and the grape family Vitaceae. These projects have involved postdoctoral fellows and curators in the Department of Botany at NMNH (J. Skog, Funk, L. Skog, Wagner, and Wen, respectively). Additionally, we have been using microsatellite profiling for application to species and population level questions with colleagues including graduate students from the University of Maryland. Most recently, we have begun using Next Generation DNA Sequencing to resolve evolutionary relationships among species undergoing rapid radiations.