Year of Award

2025

Document Type

Dissertation

Degree Type

Doctor of Philosophy (PhD)

Degree Name

Ecology and Evolution

Department or School/College

Division of Biological Sciences

Committee Chair

Lila Fishman

Commitee Members

Jeffrey Good, Zachary Cheviron, Anna Sala, John K. Kelly

Keywords

Adaptation, Evolution, Genetics

Abstract

The push and pull between recombination and selection shapes the structure of adaptive genomic variation. By mapping the genetic architecture and genetic basis of traits, we can test theoretical predictions about the nature of adaptation on the landscape. Furthermore, investigating the genetics of repeated evolutionary transitions sheds light on the nature of parallel evolution: are adaptations constrained at the molecular level, or are there many genetic paths to the same phenotype? In this dissertation I explore the genetic and phenotypic variation in the yellow monkeyflower Mimulus guttatus, which occupies Yellowstone National Park’s complex geothermal mosaic. In Chapter 1, I identify divergence in critical photoperiod requirements for M. guttatus flowering associated with geothermal habitat which recapitulates range-wide variation in the species complex. I then map the genomic basis of this critical photoperiod variation, characterize candidate genes, and identify environmental variables shaping flowering phenology in the field. In Chapter 2, I explore the population genomics and evolutionary history of a large inversion on chromosome 5 which is polymorphic across the M. guttatus complex and within Yellowstone National Park. Through genomic analyses at multiple spatial scales, I uncover inv5’s complex history, in which gene flux and selection have shaped heterogeneous molecular divergence and diversity across the inversion length. Finally, in Chapter 3 I characterize variation in floral morphology and pollen viability in YNP inbred lines, revealing directional dominance towards larger flowers, tight integration of floral morphology, and a weak positive relationship between F1 pollen viability and relatedness between parents. Using the natural experiment of Yellowstone’s microgeographic mosaic, I investigate the patterns and processes shaping adaptation in a highly diverse wildflower over narrow spatial scales. Together, these chapters illuminate the process of adaptation in the face of gene flow, evolutionary dynamics of chromosomal inversions, and parallel evolution of fundamental plant traits.

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