Coalescence and genetic diversity in sexual populations under selection

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 110; no. 39; pp. 15836 - 15841
• Main Authors: Neher, Richard A., Kessinger, Taylor A., Shraiman, Boris I.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 24.09.2013; National Acad Sciences
• Subjects: Adaptation, Physiological - genetics; Alleles; Biological Sciences; Coalescence; computer simulation; Evolution; Evolutionary genetics; Gender; Genealogy; Genealogy and Heraldry; Genetic diversity; Genetic Fitness; Genetic loci; Genetic Loci - genetics; Genetic mutation; Genetic Variation; Genetics; Genetics, Population; Genomes; Humans; Linkage Disequilibrium - genetics; loci; marker-assisted selection; Models, Genetic; Mutation - genetics; Physical Sciences; Population genetics; Quantitative genetics; Recombination, Genetic; Selection, Genetic; Simulation; Hill–Robertson interference; Bolthausen–Sznitman coalescent; genealogy
• DOI: 10.1073/pnas.1309697110
• ISSN: 0027-8424; 1091-6490

In sexual populations, selection operates neither on the whole genome, which is repeatedly taken apart and reassembled by recombination, nor on individual alleles that are tightly linked to the chromosomal neighborhood. The resulting interference between linked alleles reduces the efficiency of selection and distorts patterns of genetic diversity. Inference of evolutionary history from diversity shaped by linked selection requires an understanding of these patterns. Here, we present a simple but powerful scaling analysis identifying the unit of selection as the genomic “linkage block” with a characteristic length, [Formula], determined in a self-consistent manner by the condition that the rate of recombination within the block is comparable to the fitness differences between different alleles of the block. We find that an asexual model with the strength of selection tuned to that of the linkage block provides an excellent description of genetic diversity and the site frequency spectra compared with computer simulations. This linkage block approximation is accurate for the entire spectrum of strength of selection and is particularly powerful in scenarios with many weakly selected loci. The latter limit allows us to characterize coalescence, genetic diversity, and the speed of adaptation in the infinitesimal model of quantitative genetics.