Opinion: Why Sex-Based Genomic Differentiation Should Not Be Overlooked in Population Genetics

Area of Science:

• Evolutionary biology
• Population genetics
• Genomics

Background:

• Sex-specific genomic differentiation is often overlooked in population genetics.
• Great tits (Parus major) offer extensive genomic and population data for studying sex-based differentiation.
• Existing genomic resources for other species often lack broad population sampling.

Purpose of the Study:

• To investigate sex-specific genomic differentiation in European great tit populations.
• To identify autosomal loci showing differentiation potentially linked to sex chromosomes.
• To highlight the impact of sex ratios on differentiation metrics and propose mitigation strategies.

Main Methods:

• Leveraging population-scale genomic data from multiple European great tit populations.
• Analyzing genomic differentiation between males and females at autosomal loci.
• Comparing findings with genomic data from other songbirds with characterized sex chromosomes.
• Simulating the effects of uneven sex ratios on differentiation metrics like FST.

Main Results:

• Significant differentiation was identified at an autosomal locus on chromosome 5, likely influenced by sex-linked variation.
• Uneven sex ratios in sampled populations can create false positives for adaptive differentiation.
• Autosomal loci can show high sequence similarity to sex-linked regions.

Conclusions:

• Sex-aware study designs, including balanced sex sampling and sex as a covariate, are crucial for accurate evolutionary genomic studies.
• Generating reference genomes from the heterogametic sex (females in birds) is a pragmatic approach for labs with limited resources.
• Rigorous validation of candidate loci is essential for reliable evolutionary insights.