Behavioral and genomic consequences of evolution under skewed sex ratios

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In this dissertation I combine game theoretic modeling with experimental evolution and next-generation sequencing to address the causes and consequences of male and female sexual interactions. In chapter 1, I use tug-of-war theory to model the evolution of male and female sex roles as a function of anisogamy and sex ratio, and show that individuals can diverge in how they allocate their reproductive effort based on either of these parameters. The model incorporates both within-sex competition and between-sex cooperation to demonstrate that sexual interactions underlie the evolution of sexually dimorphic behaviors. In chapter 2, I perform experimental evolution in the laboratory using a nematode with a short generation time, Caenorhabditis remanei, and test an extension of the hypothesis that disrupting male-female interactions has cascading effects on reproductive behavior and gamete investment. By systematically altering the adult sex ratio of replicate populations over 50 generations, I show that males and females increase their mating effort when exposed to a population with an excess of males, but find no effects on their sperm and egg sizes. Chapter 3 extends this experiment by applying a genomic lens to this organism and exploring the consequences of a skewed sex ratio on populations, along with the potential for repeatable evolution in replicate populations faced with identical environmental conditions. I show that populations with a male-biased sex ratio tend towards higher genomic divergence compared to female-biased populations, and that parallel evolution can arise across experimental populations regardless of sex ratio, with implications for the predictability of evolutionary trajectories at short evolutionary timescales. Furthermore, I identify loci that change in allele frequency in opposite directions in male-biased and female-biased populations and are implicated in male mating behavior, indicating possible genes under sexual conflict in this system.

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113 pages


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Caenorhabditis; experimental evolution; game theory; parallel evolution; sex role; sexual conflict


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Union Local


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Reeve, Hudson Kern

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Shaw, Kerry L.
Dickinson, Janis Lou
Webster, Michael

Degree Discipline

Neurobiology and Behavior

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Ph. D., Neurobiology and Behavior

Degree Level

Doctor of Philosophy

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Government Document




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Attribution-NonCommercial-NoDerivatives 4.0 International


dissertation or thesis

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