Evolutionary history of recombination on sex chromosomes and of sex-biased gene expression

Males and females within a species are often under different selection pressures, which can affect both gene sequence and expression. Sex differences in selection are predicted to precipitate sex chromosome formation, and the rate of recombination on sex chromosomes varies greatly across taxa. Examining the extent of recombination suppression on sex chromosomes across closely related species can offer insight into the forces shaping sex differences and sex chromosome evolution over time. Additionally, sex-biased genes are thought to encode sexually dimorphic traits and are therefore a useful way to examine the effect of sex-specific selection across the genome. In this thesis, I use whole genome and transcriptome sequencing data to characterise the structure and conservation of sex chromosome systems across related species. I combine this with patterns of sex-specific single nucleotide polymorphisms to uncover the degree of recombination suppression and divergence across poeciliid sex chromosomes, as well as explore the consequences of recombination arrest on gene expression patterns. Finally, I investigate the selective dynamics driving the expression and rate of sequence evolution of sex-biased genes.