Judith Mank

Full Professor

We use evolutionary, genomic, and ecological tools to ask fundamental questions related to how selection acts on males and females within a species, and how the genome responds to contradictory selection to encode sexually dimorphic phenotypes. Sexual dimorphism is observed in a broad range of traits, including morphology, physiology, behaviour and life history, and is the most common form of intra-specific diversity in animals. It is also increasingly clear that sexual dimorphism has important implications to adaptation and speciation as well as human health.

How is the genome shaped by sexual selection?

The genome is subject to different sexual selection pressures depending on mating system, and we use population genomic tools to identify the strength and specific targets of sex-specific selection across different behavioural ecologies. Our results show that sexual selection is as important a force as natural selection in shaping broad patterns of gene sequence, expression and genome evolution, and that the genome can quickly respond to resolve sexual conflict via sex-specific gene regulation.

How does sexual selection influence sex chromosome evolution?

There is a complex relationship intertwining sexual selection, sexual conflict and sex chromosome evolution. Once formed, sex chromosomes are the only regions of the genome that differ in presence or dose between females and males, and are therefore predicted to become genomic hotspots for sexual conflict. However, sexual conflict is also thought to precipitate the formation of the sex chromosomes. We use genomic and transcriptomic comparisons between the sex chromosomes and autosomes to differentiate cause from effect in the relationship between sexual conflict and sex chromosomes, and to critically test the role of sex chromosomes in encoding sexually dimorphic traits. We also use natural vatiation in sexual selection to evaluate the role of sexual conflict in sex chromosome formation.

How does transcriptional dimorphism encode phenotypic dimorphism?

In order to identify the genomic targets of sexual selection, we must understand how the genome encodes dimorphic phenotypes. Central to this question is the problem of how divergence occurs between the sexes within a species when so much of the genome is shared. It is clear that although some aspects of dimorphism result from genes present in one sex on Y chromosomes, the majority of dimorphism is the product of different expression in males and females of genes that are present in both sexes (sex-biased genes). We combine sequence and expression data, and integrate these with an organismal understanding of phenotypic sex differences to test the predictions linking sex-biased gene expression and sexual dimorphism across multiple levels of biological diversity, including through development, within populations, across populations, and among species.