Natural Selection Constrains Neutral Diversity across A Wide Range of Species

Summary

The neutral theory of molecular evolution predicts that the amount of neutral polymorphisms within a species will increase proportionally with the census population size (Nc). However, this prediction has not been borne out in practice: while the range of Nc spans many orders of magnitude, levels of genetic diversity within species fall in a comparatively narrow range. Although theoretical arguments have invoked the increased efficacy of natural selection in larger populations to explain this discrepancy, few direct empirical tests of this hypothesis have been conducted. In this work, we provide a direct test of this hypothesis using population genomic data from a wide range of taxonomically diverse species. To do this, we relied on the fact that the impact of natural selection on linked neutral diversity depends on the local recombinational environment. In regions of relatively low recombination, selected variants affect more neutral sites through linkage, and the resulting correlation between recombination and polymorphism allows a quantitative assessment of the magnitude of the impact of selection on linked neutral diversity. By comparing whole genome polymorphism data and genetic maps using a coalescent modeling framework, we estimate the degree to which natural selection reduces linked neutral diversity for 40 species of obligately sexual eukaryotes. We then show that the magnitude of the impact of natural selection is positively correlated with Nc, based on body size and species range as proxies for census population size. These results demonstrate that natural selection removes more variation at linked neutral sites in species with large Nc than those with small Nc and provides direct empirical evidence that natural selection constrains levels of neutral genetic diversity across many species. This implies that natural selection may provide an explanation for this longstanding paradox of population genetics.

Related articles

• Life Processes

  This document discusses the characteristics that differentiate living organisms from non-living things, emphasizing the importance of life processes such as nutrition, respiration, and excretion necessary for maintaining life.

• Modulating plant growth-metabolism coordination for sustainable agriculture

  This article explores the co-regulatory mechanisms of plant growth, nitrogen assimilation, and carbon fixation, highlighting the balance between GROWTH-REGULATING FACTOR 4 (GRF4) and DELLA proteins in rice and its implications for sustainable agriculture.

• Bayesian inference of reassortment networks reveals fitness benefits of reassortment in human influenza viruses

  This document introduces a coalescent-based model to study reassortment in human influenza viruses, analyzing genetic diversity and fitness benefits derived from reassortment events.

• Hormonal Control of Glycogen Metabolism

  This document explores the hormonal regulation of glycogen metabolism, detailing how insulin, glucagon, and epinephrine control glycogen synthesis and breakdown to maintain blood glucose levels and energy supply.

• Nature of Matter: Elements, Compounds, and Mixtures

  This document is a textbook chapter aimed at Grade 8 students, explaining the concepts of matter, mixtures, elements, and compounds, including their properties and examples from everyday life.