A supergene-linked estrogen receptor drives alternative phenotypes in a polymorphic songbird Open Access

Merritt, Jennifer (Fall 2020)

Permanent URL: https://etd.library.emory.edu/concern/etds/t435gf32g?locale=en


Behavioral evolution relies on genetic changes, yet few behaviors can be traced to specific genetic sequences in vertebrates. Here, we show experimental evidence that differentiation of a single gene has contributed to the evolution of divergent behavioral phenotypes in the white-throated sparrow, a common backyard songbird. In this species, a series of chromosomal inversions has formed a supergene that segregates with an aggressive phenotype. The supergene has captured ESR1, the gene that encodes estrogen receptor alpha (ER-alpha); as a result, this gene is accumulating changes that now distinguish the supergene allele from the standard allele. Our results show that in birds of the more aggressive phenotype, ER-alpha knockdown caused a phenotypic change to that of the less aggressive phenotype. Next, we showed that in a free-living population, aggression is predicted by allelic imbalance favoring the supergene allele. Finally, we identified cis-regulatory features, both genetic and epigenetic, that explain the allelic imbalance. This work provides a rare illustration of how genotypic divergence has led to behavioral phenotypic divergence in a vertebrate.

Table of Contents

Acknowledgments                                                                                                    vii

Table of Contents                                                                                                     ix

List of Tables                                                                                                            x

List of Figures                                                                                                           xi

List of Symbols and Abbreviations                                                                       xii

Introduction                                                                                                              1

Methods                                                                                                                     5

Results                                                                                                                       10

Discussion                                                                                                                 20

References                                                                                                                 24

Appendix                                                                                                                   36

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