Variation in Volatile Emission in Mimulus guttatus and Implications for Plant-Insect Interactions

Abstract

The volatile compounds emitted from plants function as key host-location cues for their insect visitors. Floral volatiles guide pollinators to nectar and pollen, and in turn, pollinators initiate plant reproduction, potentially promoting a mutualistic interaction. Constitutive and herbivore-induced foliar volatiles function as an important plant defense by deterring herbivores and attracting natural enemies of herbivores. Given the importance of plant volatiles in insect behavior, variation in volatile phenotypes is expected to affect insect visitation patterns, and consequently, plant reproductive success and susceptibility to herbivores. Inbreeding is an important source of genetic variation that it is extremely common in natural populations of flowering plants. Since inbreeding increases homozygosity, inbreeding could increase expression of recessive alleles that disrupt biosynthesis of volatile compounds. In previous work, inbreeding in the mixed-mating herb Mimulus guttatus (yellow monkeyflower) decreased pollinator attraction and resistance to herbivory. However, the plant traits underlying these effects are This dissertation is one of only a few studies to examine effects of inbreeding on plant volatile profiles, and it is the first study to demonstrate that innate olfactory preferences of bumblebees can override learned preferences for floral scents. It is also among the first to differentiate the responses of specialist and generalist herbivores to inbreeding effects in their host. The findings in this dissertation enhance our understanding of the ecology and evolution of plant-insect interactions, which can have important implications for the evolution of plant mating systems and the vulnerability of small populations.