How does sexual selection shape a genome?
December 18, 2013 4:37: pm | by Matthew Hills
Matt Gage (UEA), Saskia Hogenhout (JIC)
Sexual selection, Darwin’s second great idea, is an evolutionary force that acts on almost every species on earth involved in the struggle to sexually reproduce. In this ELSA project, we will aim to understand how sexual selection acts on the genome. The big question we ultimately plan to answer is whether sexual selection acts right across the genome (because all traits are important for achieving reproduction: the ‘Genic Capture’ theory), or whether it acts just on reproductive traits (Darwin’s theory), or indeed that it does not change the genome, but works via differential expression. It is important to understand how sexual selection works, not just because it concerns every species on earth, but also because we need to quantify the importance of this process for maintaining the genetic health of populations under increasing environmental stress.
To answer this question experimentally, we have an excellent resource in replicate lines of the flour beetle Tribolium castaneum (pictured), which have been evolving in the lab for more than 8 years under experimentally controlled levels of either very high or very low sexual selection, creating adult conditions that profoundly vary the levels of male-male competition and female choice for reproduction. We already know that individuals within these populations have evolved and diverged in important ways relating to reproduction, and that populations under high sexual selection appear to have been more effectively purged of their mutational load. Because the Tribolium genome has already been sequenced and is well annotated, we can now also resequence the genomes of these experimentally-evolved populations, and compare how much, and where, the genomes have changed under divergent intensities of sexual selection.
To test the Genic Capture theory: that populations evolving from a common ancestor under sole variation in the intensity of sexual selection will show significant and widespread genomic divergence.
With TGAC and the NERC Biomolecular Analysis Facilities, we aim to achieve 10x coverage of the resequenced genomes from replicate individuals from our High and Low sexual selection lines, comparing SNP changes to their ancestral Ga-1 population, and a control. Detailed coverage of the published Tribolium genome is available at http://beetlebase.org, with bio-informatics focusing on measures of variance in SNP changes between lines versus between regimes.
Copulating Tribolium flour beetles: after experimentally evolving populations under sole variation in sexual selection, this project will assess the effect of sexual selection upon genome evolution.