A central goal in evolutionary biology is to understand how organisms adapt to their environments. Progress toward this goal requires an interdisciplinary set of experiments that connects the ecological significance of putatively adaptive traits with a functional characterization of their genetic basis. My research investigates the evolutionary consequences of transitions in flower color, with a focus on the phenotypically variable species, Mimulus aurantiacus. Evolutionary transitions in flower color are numerous, and it often is thought that flower color differences between populations or species are adaptive because of their prominent role in the attraction of animal pollinators. Moreover, the molecular basis of the flavonoid biosynthetic pathway that controls anthocyanin pigmentation patterns is extremely well-characterized, which allows me to apply molecular tools to characterize gene function. Thus, this research program is truly integrative, as it combines studies of field biology to measure the stength of natural selection with molecular genetic and genomic approaches to connect genotype with phenotype and fitness in natural plant populations. An additional area of interest involves the molecular evolution of transcriptional regulation, especially as it relates to how functional constraint and pleiotropy determine the types of mutations fixed during evolutionary change.