Fluctuations in fitness distributions and the effects of weak linked selection on sequence evolution

TL;DR

This paper develops a theoretical framework to understand how weak linked selection influences the distribution of fitness and genetic diversity in evolving populations, extending previous models from strong to weak selection regimes.

Contribution

It introduces a perturbative approach to analyze fitness distribution and genetic diversity under weak selection, providing exact analytical predictions.

Findings

Quantifies stochastic behavior of fitness distribution under weak selection

Provides analytical predictions for sequence diversity and substitution rates

Extends models from strong to weak selection regimes

Abstract

Evolutionary dynamics and patterns of molecular evolution are strongly influenced by selection on linked regions of the genome, but our quantitative understanding of these effects remains incomplete. Recent work has focused on predicting the distribution of fitness within an evolving population, and this forms the basis for several methods that leverage the fitness distribution to predict the patterns of genetic diversity when selection is strong. However, in weakly selected populations random fluctuations due to genetic drift are more severe, and neither the distribution of fitness nor the sequence diversity within the population are well understood. Here, we briefly review the motivations behind the fitness-distribution picture, and summarize the general approaches that have been used to analyze this distribution in the strong-selection regime. We then extend these approaches to the case of weak selection, by outlining a perturbative treatment of selection at a large number of linked sites. This allows us to quantify the stochastic behavior of the fitness distribution and yields exact analytical predictions for the sequence diversity and substitution rate in the limit that selection is weak.