An Experimental Test of the Pluralistic Approach to the Maintenance of Outcrossing Restricted; Files Only
McCauley, Michelle (Summer 2024)
Abstract
Sex is an evolutionary puzzle. Although biparental outcrossing is costly compared to uniparental reproduction, outcrossing is ubiquitous in nature. A large number of hypotheses have been put forward to explain the benefit of outcrossing over uniparental reproduction, although none can universally explain the distribution of outcrossing in nature. My dissertation uses experimental evolution with the nematode worm Caenorhabditis elegans to explore assumptions and limitations of some of these hypotheses experimentally. First, in my second chapter, I review the Red Queen hypothesis, which states that antagonistic coevolution between host and parasite can maintain outcrossing in hosts. Then, in my third chapter, I test the prediction of the Red Queen hypothesis that antagonistic fluctuating selection between coevolving hosts and parasites is the underlying mechanism for the maintenance of outcrossing. In my fourth chapter, I parameterize the space under which increased mutation rate alone can maintain outcrossing. Then, using previous data which parameterized parasite virulence as a factor of interest for the Red Queen hypothesis, I combined both increased mutation rate and a coevolving parasite to experimentally verify the pluralistic approach, under which two hypotheses acting in tandem maintain outcrossing under parameter levels where one alone cannot. In my final data chapter, I test Baker’s law, which hypothesizes that uniparental reproduction will be favored over outcrossing when organisms undergo long distance dispersal. Altogether, my dissertation contributes to our understanding of the complex patterns of outcrossing and uniparental reproduction in nature.
Table of Contents
CHAPTER I: Introduction 1
The Problem of Sex 1
An Inundation of Hypotheses for Outcrossing 3
C. elegans and Experimental Evolution 5
Summary of Chapters 9
CHAPTER II: An Audience with the Red Queen: Defining the Red Queen Hypothesis
within the Context of the Maintenance of Sex 11
1. Introduction 11
2. Assumptions of the Red Queen 14
3. Ecological Interactions Imposing Red Queen Dynamics 17
4. The Red Queen and Host-Parasite Interactions 23
5. Ecological Predictions 25
6. Diagnosing the Red Queen 27
7. Limits of the Red Queen 31
8. Conclusions 34
CHAPTER III: There’s something about coevolution: host-parasite coevolution favors
host outcrossing via antagonistic fluctuating selection 36
Introduction 36
Methods 39
Results 44
Discussion 51
Supplemental Material 54
CHAPTER IV: A pluralistic approach to sex: increased mutation rate and a coevolving
parasite maintain outcrossing 57
Introduction 58
Results and Discussion 62
Conclusion 72
Methods 73
Supplemental Material 82
CHAPTER V: An empirical test of Baker’s law: Dispersal favors increased rates of
self-fertilization 86
Introduction 86
Methods 91
Results 96
Discussion 101
Supplemental Material 104
CHAPTER VI: Conclusion 110
Summary and Discussion of Previous Chapters 110
Future Directions 112
REFERENCES 114
Literature Cited 114
Software and Packages 123
About this Dissertation
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File download under embargo until 21 August 2030 | 2024-07-19 15:36:37 -0400 | File download under embargo until 21 August 2030 |
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