- Title Pages
- Dedication
- Preface
- I Introduction
- 1 Changes in Quantitative Traits Over Time
- II Evolution at One and Two Loci
- 2 Neutral Evolution in One- and Two-Locus Systems
- 3 The Genetic Effective Size of a Population
- 4 The Nonadaptive Forces of Evolution
- 5 The Population Genetics of Selection
- 6 Theorems of Natural Selection: Results of Price, Fisher, and Robertson
- 7 Interaction of Selection, Mutation, and Drift
- 8 Hitchhiking and Selective Sweeps
- 9 Using Molecular Data to Detect Selection: Signatures from Recent Single Events
- 10 Using Molecular Data to Detect Selection: Signatures from Multiple Historical Events
- III Drift and Quantitative Traits
- 11 Changes in Genetic Variation Induced by Drift
- 12 The Neutral Divergence of Quantitative Traits
- IV Short-Term Response on a Single Character
- 13 Short-term Changes in the Mean: 1. The Breeder’s Equation
- 14 Short-term Changes in the Mean: 2. Truncation and Threshold Selection
- 15 Short-term Changes in the Mean: 3. Permanent Versus Transient Response
- 16 Short-term Changes in the Variance: 1. Changes in the Additive Variance
- 17 Short-term Changes in the Variance: 2. Changes in the Environmental Variance
- 18 Analysis of Short-term Selection Experiments: 1. Least-squares Approaches
- 19 Analysis of Short-term Selection Experiments: 2. Mixed-model and Bayesian Approaches
- 20 Selection Response in Natural Populations
- V Selection in Structured Populations
- 21 Family-Based Selection
- 22 Associative Effects: Competition, Social Interactions, Group and Kin Selection
- 23 Selection Under Inbreeding
- VI Population-Genetic Models of Trait Response
- 24 The Infinitesimal Model and Its Extensions
- 25 Long-term Response: 1. Deterministic Aspects
- 26 Long-term Response: 2. Finite Population Size and Mutation
- 27 Long-term Response: 3. Adaptive Walks
- 28 Maintenance of Quantitative Genetic Variation
- VII Measuring Selection on Traits
- 29 Individual Fitness and the Measurement of Univariate Selection
- 30 Measuring Multivariate Selection
- Appendix 1 Diffusion Theory
- Appendix 2 Introduction to Bayesian Analysis
- Appendix 3 Markov Chain Monte Carlo and Gibbs Sampling
- Appendix 4 Multiple Comparisons: Bonferroni Corrections, False-discovery Rates, and Meta-analysis
- Appendix 5 The Geometry of Vectors and Matrices: Eigenvalues and Eigenvectors
- Appendix 6 Derivatives of Vectors and Vector-valued Functions
- Literature Cited
- Author Index
- Organism and Trait Index
- Subject Index

# Long-term Response: 3. Adaptive Walks

# Long-term Response: 3. Adaptive Walks

- Chapter:
- (p.991) 27 Long-term Response: 3. Adaptive Walks
- Source:
- Evolution and Selection of Quantitative Traits
- Author(s):
### Bruce Walsh

### Michael Lynch

- Publisher:
- Oxford University Press

One model for long-term evolution is an adaptive walk, a series of fixations of mutations that moves the trait mean toward some optimal value. The foundation for this idea traces back to Fisher's geometric model, which showed that mutations of large effect are favored when a trait is far from its optimal, while smaller effects are favored as it approaches the optimal value. Under fairly general conditions, this results in a roughly exponential distribution of fixed adaptive effects. An alternative to trait-based walks are walks in fitness space, motivated by considering a series of mutations to improve the fitness of a particular sequence. In such settings, extreme value theory also suggests a roughly exponential distribution, now of fitness (instead of trait) effects, for mutations fixed during the walk. Much of this theory offers at least partial experimental testing, and this chapter describes not only the theory, but also some of the empirical work testing the models.

*Keywords:*
clonal interference, cost of complexity, cost of pleiotropy, extreme-value theory, Fisher's geometric model, Fisher-Kimura-Orr adaptive walks, Fisher–Tippett–Gnedenko theorem, Maynard-Smith-Gillespie-Orr adaptive walks, mutational landscape model, Orr's invariance result. restricted pleiotropy, selectively accessible, sign epistasis, SSWM model, universal pleiotropy

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- Title Pages
- Dedication
- Preface
- I Introduction
- 1 Changes in Quantitative Traits Over Time
- II Evolution at One and Two Loci
- 2 Neutral Evolution in One- and Two-Locus Systems
- 3 The Genetic Effective Size of a Population
- 4 The Nonadaptive Forces of Evolution
- 5 The Population Genetics of Selection
- 6 Theorems of Natural Selection: Results of Price, Fisher, and Robertson
- 7 Interaction of Selection, Mutation, and Drift
- 8 Hitchhiking and Selective Sweeps
- 9 Using Molecular Data to Detect Selection: Signatures from Recent Single Events
- 10 Using Molecular Data to Detect Selection: Signatures from Multiple Historical Events
- III Drift and Quantitative Traits
- 11 Changes in Genetic Variation Induced by Drift
- 12 The Neutral Divergence of Quantitative Traits
- IV Short-Term Response on a Single Character
- 13 Short-term Changes in the Mean: 1. The Breeder’s Equation
- 14 Short-term Changes in the Mean: 2. Truncation and Threshold Selection
- 15 Short-term Changes in the Mean: 3. Permanent Versus Transient Response
- 16 Short-term Changes in the Variance: 1. Changes in the Additive Variance
- 17 Short-term Changes in the Variance: 2. Changes in the Environmental Variance
- 18 Analysis of Short-term Selection Experiments: 1. Least-squares Approaches
- 19 Analysis of Short-term Selection Experiments: 2. Mixed-model and Bayesian Approaches
- 20 Selection Response in Natural Populations
- V Selection in Structured Populations
- 21 Family-Based Selection
- 22 Associative Effects: Competition, Social Interactions, Group and Kin Selection
- 23 Selection Under Inbreeding
- VI Population-Genetic Models of Trait Response
- 24 The Infinitesimal Model and Its Extensions
- 25 Long-term Response: 1. Deterministic Aspects
- 26 Long-term Response: 2. Finite Population Size and Mutation
- 27 Long-term Response: 3. Adaptive Walks
- 28 Maintenance of Quantitative Genetic Variation
- VII Measuring Selection on Traits
- 29 Individual Fitness and the Measurement of Univariate Selection
- 30 Measuring Multivariate Selection
- Appendix 1 Diffusion Theory
- Appendix 2 Introduction to Bayesian Analysis
- Appendix 3 Markov Chain Monte Carlo and Gibbs Sampling
- Appendix 4 Multiple Comparisons: Bonferroni Corrections, False-discovery Rates, and Meta-analysis
- Appendix 5 The Geometry of Vectors and Matrices: Eigenvalues and Eigenvectors
- Appendix 6 Derivatives of Vectors and Vector-valued Functions
- Literature Cited
- Author Index
- Organism and Trait Index
- Subject Index