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This study develops a new method to quantify the relative contributions of genetic drift versus natural selection to evolutionary change over a single generation by analyzing how allele frequency changes relate to linkage disequilibrium patterns across the genome. Applying this framework to UK Biobank data using fitness proxy phenotypes, the researchers found that while polygenic selection does make a statistically significant contribution to allele frequency changes, genetic drift accounts for the vast majority of genome-wide variation in a single generation. The method leverages the principle that alleles in stronger linkage disequilibrium with selected alleles show greater variance in frequency change than expected under drift alone.
Why it matters
This framework provides a way to measure short-term evolutionary dynamics in humans and other organisms where generational data is available, addressing a long-standing gap in evolutionary biology that has primarily focused on long-term timescales. The approach could enable researchers to track polygenic selection in real-time across diverse species, improving our understanding of how populations adapt to environmental changes.
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⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
The relative importance of genetic drift versus selection to evolutionary change has long been debated. This debate has mainly focused over long-time-scales (e.g. hundreds of thousands of generations), leaving the question of short-term evolutionary change relatively unaddressed. Our knowledge about the effects of selection on genetic change over short time scales is often based on identifying major allele frequency changes at few loci with large selective advantage. Yet selection often acts on polygenic traits where the short-term response is shaped by small shifts in allele frequency at many loci that will be difficult to distinguish from genetic drift. Here, we quantify the genome-wide effects of polygenic selection over a single generation, using the idea that alleles in stronger genetic correlation (LD) with selected alleles are expected to show greater variance in allele frequency change than expected under genetic drift. We derive expressions relating variation in LD among loci to the variance in allele frequency change due to linked selection and genetic drift and leverage this theory to quantify the contribution of linked selection to a single generation of allele frequency change. To demonstrate our approach, we decompose the genome-wide allele frequency change in the UK Biobank using fitness proxy phenotypes. We show that selection makes a small, but significant, contribution, with genetic drift making up the large majority of the change in allele frequencies. Our framework could be applied to other organisms for which data on number of offspring or allele frequencies over consecutive generations are available, enabling investigations of the short-term, genome-wide effects of polygenic selection across a wide range of species.
Source: The Genome-Wide Effect of Drift and Selection over a Single Generation