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Thesis

Mating system, sex-specific selection and the evolution of the avian sex chromosomes

Abstract:

Sex chromosomes experience distinct evolutionary environments, due to their unusual pattern of inheritance, and studies of sex chromosome evolution can shed light on the fundamental evolutionary forces acting across the genome as a whole. Here, I combine genomic and transcriptomic data across a wide range of avian species to explore the evolutionary processes governing sex chromosome evolution. Birds are female heterogametic and therefore it is possible, via comparisons with male heterogametic species, to identify the fundamental factors driving sex chromosome evolution, versus those associated with sex.

In this thesis, I uncover a complex mosaic of recombination suppression between the Z and W chromosomes, characterized by repeated and independent divergence of gametologs, together with ongoing genetic exchange. Additionally, I highlight the role of mating system, and interplay between evolutionary forces, in driving coding and expression evolution on the Z and W chromosomes. My findings indicate that although the Z chromosome is masculinized for male-specific effects, the magnitude of genetic drift acting on Z-linked genes is elevated in promiscuous relative to monogamous mating systems. In contrast, evolution of the female-limited W chromosome is governed predominately by purifying selection. Together, my results suggest that the role of the Z chromosome in encoding sexual dimorphisms may be limited, but that W-linked genes play a significant role in female-specific fitness. In conclusion, my findings reveal the power of mating system in shaping broad patterns of genome evolution.

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Institution:
University of Oxford
Division:
MPLS
Department:
Zoology
Oxford college:
Linacre College
Role:
Author

Contributors

Institution:
University of Oxford
Division:
MPLS
Department:
Zoology
Role:
Supervisor
Institution:
University of Oxford
Division:
MPLS
Department:
Zoology
Role:
Supervisor

Publication date:
2014
Type of award:
DPhil
Level of award:
Doctoral
Awarding institution:
University of Oxford

Language:
English
Keywords:
Subjects:
UUID:
uuid:89079fac-7196-4c15-ac0e-ceae0c4b0264
Local pid:
ora:12229
Deposit date:
2015-09-08

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