The genus Mimulus has served as a model system for the study of mating system evolution for more than a century. Charles Darwin's pioneering experimental work on M. luteus provided strong evidence for inbreeding depression, and suggested that the magnitude of inbreeding depression may decline following several generations of inbreeding. In the mid-20th century, Robert Vickery Jr. initiated a broad program of evolutionary research in the genus, including work on the evolution of reproductive isolation through pollinator fidelity. This symposium honors Dr. Vickery's many accomplishments. During the last two decades work by many research groups has addressed diverse aspects of mating system evolution, including: the genetic basis of inbreeding depression; measurement of inbreeding depression in the wild, the role of herbivores in inbreeding depression and the potential interaction between inbreeding level and expression of phenotypic plasticity on colonizing success. There has also been considerable research concerning patterns of variation in selfing rates within and among populations and how selfing may act as a barrier to gene flow. Some of the factors influencing selfing rates include floral morphology, population density, and floral display size. Other work has examined pollinator responses to floral design and display, and has addressed how these factors influence patterns of paternity. Research has also examined the quantitative genetic basis of floral traits. Quantitative trait loci have been mapped to elucidate the genetics underlying floral adaptations and speciation in the genus. This symposium highlights many of these exciting discoveries.

Key words: Mimulus , floral traits, gene flow, inbreeding depression, mating system, self-fertilization