Rapid Evolutionary Adaptation in Response to Selection on Quantitative Traits.

Wolfgang Stephan

doi:10.3390/life11080797

Abstract

Evolutionary adaptation after sudden environmental changes can occur very rapidly. The mechanisms facilitating rapid adaptation range from strong positive directional selection leading to large shifts in the allele frequencies at a few loci (selective sweeps) to polygenic selection causing small changes in allele frequencies at many loci. In addition, combinations of these two extreme mechanisms may also result in fast evolution. In recent years, following reports of new case studies of rapid adaptation, population genetic models have been proposed to explain these observations. In these models, the role of the major selective forces (positive directional and stabilizing selection) is highlighted as well as the genetic architecture of quantitative traits. Furthermore, the factors limiting the speed of adaptation are analyzed, in particular, the effects of random genetic drift and demography due to finite population size.

Highlights

We review the theoretical work on rapid adaptation based on a model of a single quantitative trait that was analyzed by de Vladar and Barton [27], Jain and Stephan [29,30,31], John and Stephan [33], and Stephan and John [35]
To describe the dynamics of rapid adaptation based on our deterministic model, we assume that the population is in equilibrium with no deviation from the phenotypic optimum located at z0 [27]
When the effect sizes are small, subtle to moderate allele frequency shifts occur within the phase of fast adaptation

Summary

Introduction

We review the theoretical work on rapid adaptation based on a model of a single quantitative trait that was analyzed by de Vladar and Barton [27], Jain and Stephan [29,30,31], John and Stephan [33], and Stephan and John [35] This model covers the entire range of genetic architectures, from a few loci of major effects to the highly polygenic case, and has been studied for very large (infinite) populations and for populations of finite size

Deterministic Model

Two Extreme Scenarios of Rapid Adaptation

The Role of Genetic Drift in Rapid Adaptation

Equilibrium

Findings

Discussion