SpeSex · Does natural selection align with sexual selection to promote reproductive isolation in different environments? An experimental approach

Understanding the drivers of reproductive isolation between populations lies at the core of evolutionary biology and is central to understanding how speciation occurs. Natural selection has been traditionally considered a major force driving speciation, but other forces can hamper or reinforce the impact of natural selection on adaptation, including sexual selection. So far, theoretical and empirical studies have produced mixed findings about the extent to which natural and sexual selection act jointly or in opposition to drive reproductive isolation, and hence speciation. Experimental evolution is a powerful tool to test the combined effect of natural and sexual selection to drive population divergence. In this action, I will use seed beetle Acanthoscelides obtectus from long-term experimental evolution lines, which have differed in environmental condition and selective pressures, to explore reproductive isolation as driven by the interaction between local adaptation to a novel environment and sexual selection/conflict. In a novel framework combining phenotypic-level measurements with genomic tools, I will quantify (a) the extent of pre-zygotic reproductive isolation between populations under different environmental regimes; (b) the extent of post-zygotic reproductive isolation, by determining the extent to which hybrid eggs and offspring are of lower fitness than non-hybrids; and (c) gene expression and selection pressures associated with the novel environment at loci associated with natural and sexual selection, which are putative sources of reproductive isolation. This project represents a major advance in our understanding of the role of multiple selective forces in driving species diversity.