UC Riverside

Environmental adaptation is a critical component for the survival of plant species. Understanding how genetic diversity is purged and preserved during evolution and the types of traits which contribute to fitness increases over large time spans helps clarify the relationships between genotypic and phenotypic variance. Throughout this dissertation I use the Composite Cross II evolution experiment in barley to explore the process of evolution to novel environments over the course of nearly a century and connect genotype with phenotype. The seed bank of this population provides unprecedented access to the story of evolution in a valuable model crop species. In Chapter 1 I show how the connection between flowering time and fecundity depends upon environmental factors. In Chapter 2 I expand the scope to explore additional physical, developmental traits that contribute to competitive ability in the experiment. In Chapter 3 I explore how genetic diversity stored in the population helps preserve its fitness during radical environmental changes and that some of the genetic controls and pathways under selection in the original environment undergo a reversal in response to new selective pressures.