Quantitative trait evolution in Mimulus guttatus (yellow monkeyflower)

Abstract

My dissertation examines several aspects of quantitative trait evolution in Mimulus guttatus. In Chapter 2, I use M. guttatus plants to investigate how response to artificial selection on a trait index differs among replicate populations that differ only in mating system. The results show a divergence in response to selection among mating system types, despite an equivalent selection regime and no direct effect of mating system on fitness. In Chapter 3, I use plants derived from several natural populations to look at geographic differences in genetic and environmental variation in a quantitative trait, trichome density. Constitutive production of trichomes is variable both within and among populations of M. guttatus and there is genetic variation for it both within and among geographically distinct natural populations. Damage on early leaves can induce increased trichome production on later leaves, a plastic response that is likely adaptive. In addition, I show in this chapter that trichome induction can be maternally transmitted by a yet undescribed epigenetic mechanism. There is genetic variation among plants in the capacity for both within and between plant generation induction. In Chapter 4, I examine how trichome density affects plant-insect interactions with an herbivore common to some M. guttatus populations, the meadow spittlebug. While trichomes confer resistance to some forms of herbivory, these experiments show that they do not deter meadow spittlebugs, either in their ability to feed or in their feeding preferences.