The Cost of Survival: Male Competition in Light of Evolutionary History Restricted; Files Only

Abstract

Sexual reproduction is evolutionary costly, but its prevalence has generated theories which attempt to explain its maintenance in nature. One of these theories is the Red Queen hypothesis which postulates that as hosts are coevolving with parasites, they maintain a biparental mode of sexual reproduction when the costs of the parasite outweigh the benefits of asexual reproduction. The Hamilton-Zuk hypothesis extends this coevolving dynamic to parasite-mediated sexual selection in which females use males’ secondary sexual characters to evaluate male vigor and resistance to parasites. To explore the intersection of sexual conflict and selection for parasite resistance, we use male C. elegans to test the role of selective pressures imposed by coevolving parasites in the evolution of male competition. Here, we competed experimental males with differing evolutionary histories (coevolved, evolved, and non-evolved on the parasite S. marcescens) against RFP-labeled tester males to reveal changes in male competition. The effect of the treatments on male competition across the populations was not consistent. On a population level, we observed more experimental male competitiveness in sexual conflicts against the RFP-labeled tester males, suggesting that population was a greater predictor of the change in male competitive ability than treatment. Characterizing male competition demonstrates the evolutionary role of male C. elegans in hosts exposed to parasites, framed by the Red Queen and Hamilton-Zuk hypotheses. More investigation is necessary to elucidate the connection between male tail morphology and male sexual behavior to analyze the genetic basis of parasite resistance and male competition.

Table of Contents

Table of Contents

 

Introduction……………………………………………………………………………………1

 

Materials and Methods..………………………………………………..…………….….……6

a.    Statistical Analysis Methods………………………………………………….……10

 

Results…………………………………………………………………….………...…………11

 

Discussion……………………………………………………………….…….………………15

 

Addendum………………………………………………………….…….…………………….21

a.    Mating systems and genetic manipulations…………………….……………………...21

References……………………………………………………………………………………..22

 

Figures

a.    Figure 1: Schematic representing the possible interactions between sexual selection and selection for resistance………………………………………………………….5

b.    Figure 2: Schematic representing the relationship between the ancestral, coevolved, evolved and control treatments used for the experiment……………………………8

c.    Figure 3: Total offspring counts by treatment (ancestral, coevolution, control, evolution)……………………………………………………………………………13

d.    Figure 4: Percent RFP-labeled offspring change from the ancestor, across treatment groups (control, evolution, and coevolution) and across five populations…………14

About this Honors Thesis

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School	Emory College
Department	Biology
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Biology, Evolution and Development Biology, Ecology
Keyword	Red Queen evolutionary biology experimental evolution parasite-mediated sexual selection C. elegans male competition Hamilton-Zuk
Committee Chair / Thesis Advisor	Levi Morran, Emory University
Committee Members	Michael McCormick, Emory University Michal Arbilly, Emory University

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