The stunning biodiversity found on Earth ultimately arose through the fundamental process of speciation. While biologists have long been fascinated by species origination, there are many important unanswered questions. Among these, a central question to speciation research is what kinds of barriers most commonly drive the process, and particular debate has surrounded the relative importance of pre- versus postzygotic barriers. Prezygotic barriers are those that limit hybrid formation, while postzygotic barriers involve reduced hybrid fitness. The proposed study will examine the strength of multiple forms of reproductive isolation in ten recently diverged species pairs in the genus Mimulus (monkeyflowers). A variety of field, greenhouse, and laboratory methods will be employed to examine prezygotic barriers including differences in habitat, timing of reproduction, pollinators, and gametic compatibility. Postzygotic barriers will be assessed by performing experimental hybridizations in the laboratory and greenhouse. Additionally, patterns of current and historical gene flow will be examined and compared to measures of current isolation. This project will also serve to train undergraduates, including individuals from underrepresented groups. In addition, the results of this study will be used to enhance secondary school teaching in the local school district.
