STABILITY OF THE G-MATRIX IN A POPULATION EXPERIENCING PLEIOTROPIC MUTATION, STABILIZING SELECTION, AND GENETIC DRIFT

Evolution ◽  
2003 ◽  
Vol 57 (8) ◽  
pp. 1747 ◽  
Author(s):  
Adam G. Jones ◽  
Stevan J. Arnold ◽  
Reinhard Bürger
Keyword(s):  
Genetic Drift ◽  
Stabilizing Selection ◽  
Pleiotropic Mutation

Inferring natural selection in a fossil threespine stickleback

Paleobiology ◽  
2006 ◽  
Vol 32 (4) ◽  
pp. 562-577 ◽  
Author(s):  
Michael A. Bell ◽  
Matthew P. Travis ◽  
D. Max Blouw
Keyword(s):  
Natural Selection ◽  
Random Process ◽  
Genetic Drift ◽  
Fossil Record ◽  
Evolutionary Biology ◽  
Threespine Stickleback ◽  
Stabilizing Selection ◽  
Persistent Problem ◽  
Selection For ◽  
Lines Of Evidence

Inferring the causes for change in the fossil record has been a persistent problem in evolutionary biology. Three independent lines of evidence indicate that a lineage of the fossil stickleback fish Gasterosteus doryssus experienced directional natural selection for reduction of armor. Nonetheless, application to this lineage of three methods to infer natural selection in the fossil record could not exclude random process as the cause for armor change. Excluding stabilizing selection and genetic drift as the mechanisms for biostratigraphic patterns in the fossil record when directional natural selection was the actual cause is very difficult. Biostratigraphic sequences with extremely fine temporal resolution among samples and other favorable properties must be used to infer directional selection in the fossil record.

scholarly journals The statistical mechanics of a polygenic character under stabilizing selection, mutation and drift

2010 ◽  
Vol 8 (58) ◽  
pp. 720-739 ◽  
Author(s):  
Harold P. de Vladar ◽  
Nick H. Barton
Keyword(s):  
Population Genetics ◽  
Statistical Mechanics ◽  
Generating Function ◽  
Genetic Drift ◽  
Infinite Series ◽  
Genetic Variance ◽  
Directional Selection ◽  
Entropy Measure ◽  
Stabilizing Selection ◽  
Approximation Procedure

By exploiting an analogy between population genetics and statistical mechanics, we study the evolution of a polygenic trait under stabilizing selection, mutation and genetic drift. This requires us to track only four macroscopic variables, instead of the distribution of all the allele frequencies that influence the trait. These macroscopic variables are the expectations of: the trait mean and its square, the genetic variance, and of a measure of heterozygosity, and are derived from a generating function that is in turn derived by maximizing an entropy measure. These four macroscopics are enough to accurately describe the dynamics of the trait mean and of its genetic variance (and in principle of any other quantity). Unlike previous approaches that were based on an infinite series of moments or cumulants, which had to be truncated arbitrarily, our calculations provide a well-defined approximation procedure. We apply the framework to abrupt and gradual changes in the optimum, as well as to changes in the strength of stabilizing selection. Our approximations are surprisingly accurate, even for systems with as few as five loci. We find that when the effects of drift are included, the expected genetic variance is hardly altered by directional selection, even though it fluctuates in any particular instance. We also find hysteresis, showing that even after averaging over the microscopic variables, the macroscopic trajectories retain a memory of the underlying genetic states.

Isolation by distance in a quantitative trait.

Genetics ◽  
1991 ◽  
Vol 128 (2) ◽  
pp. 443-452 ◽  
Author(s):  
R Lande
Keyword(s):  
Genetic Drift ◽  
Genetic Variance ◽  
Two Dimensions ◽  
Quantitative Character ◽  
Stabilizing Selection ◽  
Neighborhood Size ◽  
Phenotypic Variance ◽  
Two Dimensional ◽  
Random Genetic Drift ◽  
Dispersal Function

Abstract Random genetic drift in a quantitative character is modeled for a population with a continuous spatial distribution in an infinite habitat of one or two dimensions. The analysis extends Wright's concept of neighborhood size to spatially autocorrelated sampling variation in the expected phenotype at different locations. Weak stabilizing selection is assumed to operate toward the same optimum phenotype in every locality, and the distribution of dispersal distances from parent to offspring is a (radially) symmetric function. The equilibrium pattern of geographic variation in the expected local phenotype depends on the neighborhood size, the genetic variance within neighborhoods, and the strength of selection, but is nearly independent of the form of the dispersal function. With all else equal, geographic variance is smaller in a two-dimensional habitat than in one dimension, and the covariance between expected local phenotypes decreases more rapidly with the distance separating them in two dimensions than in one. The equilibrium geographic variance is less than the phenotypic variance within localities, unless the neighborhood size is small and selection is extremely weak, especially in two dimensions. Nevertheless, dispersal of geographic variance created by random genetic drift is an important mechanism maintaining genetic variance within local populations. For a Gaussian dispersal function it is shown that, even with a small neighborhood size, a population in a two-dimensional habitat can maintain within neighborhoods most of the genetic variance that would occur in an infinite panmictic population.

Frequency-dependent selection, metrical characters and molecular evolution

1988 ◽  
Vol 319 (1196) ◽  
pp. 631-640 ◽  
Keyword(s):  
Molecular Evolution ◽  
Genetic Drift ◽  
Random Order ◽  
Quantitative Character ◽  
Stabilizing Selection ◽  
Molecular Clocks ◽  
Random Genetic Drift ◽  
Stochastic Effects ◽  
Frequency Dependent ◽  
Frequency Dependent Selection

Computer models of selection acting on a quantitative character show that a combination of frequency-dependent and stabilizing selection can maintain many polymorphisms among the genes that determine the character. The models also show that the random order of mutations can give rise to selectively driven stochastic effects that are sometimes more important than random genetic drift. They suggest simple explanations for patterns of divergence between populations and species, and for apparent discrepancies between the rates of morphological and molecular evolution. They point towards a selective theory of ‘molecular clocks’

scholarly journals On the distribution of the mean and variance of a quantitative trait under mutation-selection-drift balance.

Genetics ◽  
1994 ◽  
Vol 138 (3) ◽  
pp. 901-912 ◽  
Author(s):  
R Bürger ◽  
R Lande
Keyword(s):  
Genetic Drift ◽  
Quantitative Trait ◽  
Quantitative Traits ◽  
Genetic Variance ◽  
Stochastic Simulations ◽  
Stabilizing Selection ◽  
Phenotypic Evolution ◽  
Theoretical Predictions ◽  
Mean And Variance ◽  
The Mean

Abstract The distributions of the mean phenotype and of the genetic variance of a polygenic trait under a balance between mutation, stabilizing selection and genetic drift are investigated. This is done by stochastic simulations in which each individual and each gene are represented. The results are compared with theoretical predictions. Some aspects of the existing theories for the evolution of quantitative traits are discussed. The maintenance of genetic variance and the average dynamics of phenotypic evolution in finite populations (with Ne < 1000) are generally simpler than those suggested by some recent deterministic theories for infinite populations.

scholarly journals THE SELECTIVE VALUE OF ALLELES UNDERLYING POLYGENIC TRAITS

Genetics ◽  
1984 ◽  
Vol 108 (4) ◽  
pp. 1021-1033
Author(s):  
Michael Lynch
Keyword(s):  
Molecular Evolution ◽  
Genetic Drift ◽  
Genetic Variance ◽  
Neutral Theory ◽  
Mechanistic Explanation ◽  
Neutral Evolution ◽  
Stabilizing Selection ◽  
Average Effect ◽  
Absolute Value ◽  
The Mean

ABSTRACT To define the genetic and ecological circumstances that are conductive to evolution via genetic drift at the allelic level, the selection coefficient for a constituent allele of arbitrary effect is derived for a polygenic character exposed to stabilizing selection. Under virtually all possible conditions, alleles within the class for which the absolute value of the average effect is <10-2 phenotypic standard deviations are neutral with respect to each other. In addition, when the mean phenotype is at the optimum and the genetic variance is in selection-drift-mutation equilibrium, a considerable amount of neutral evolution is expected in the class of alleles with intermediate effects on the phenotype. These results help clarify how molecular evolution via genetic drift may occur at a locus despite intense selection and provide a potential mechanistic explanation for the neutral theory of molecular evolution.

scholarly journals Adaptive Fixation in Two-Locus Models of Stabilizing Selection and Genetic Drift

Genetics ◽  
2014 ◽  
Vol 198 (2) ◽  
pp. 685-697 ◽  
Author(s):  
Andreas Wollstein ◽  
Wolfgang Stephan
Keyword(s):  
Genetic Drift ◽  
Stabilizing Selection

The Neutral Divergence of Quantitative Traits

2018 ◽  
Author(s):  
Bruce Walsh ◽  
Michael Lynch
Keyword(s):  
Gene Expression ◽  
Genetic Drift ◽  
Joint Action ◽  
Quantitative Traits ◽  
Directional Selection ◽  
Stabilizing Selection ◽  
Data Sets ◽  
Diverse Range ◽  
Over Time

The joint action of genetic drift and mutation results in the divergence of trait means over time. This chapter examines the expected amount of divergence, which forms the basis for a number of tests on whether an observed pattern is either too large relative to drift (suggesting directional selection) or two small (suggesting stabilizing selection). It then applies these results to examine tests for selection over a very diverse range of data sets, ranging from a stratophenetic series of fossils to divergence in gene expression over time. It also examines a number of trait-augmented marked-based tests (such as using the QTLs or GWAS hits for a trait) for departures from neutrality.

scholarly journals The rate and molecular spectrum of mutation are selectively maintained in yeast

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Haoxuan Liu ◽  
Jianzhi Zhang
Keyword(s):  
Natural Selection ◽  
Genetic Drift ◽  
Fundamental Question ◽  
Molecular Spectrum ◽  
Mutational Bias ◽  
Stabilizing Selection ◽  
Deleterious Mutations ◽  
Random Mutation ◽  
Evolutionary Forces ◽  
Yeast Strains

AbstractWhat determines the rate (μ) and molecular spectrum of mutation is a fundamental question. The prevailing hypothesis asserts that natural selection against deleterious mutations has pushed μ to the minimum achievable in the presence of genetic drift, or the drift barrier. Here we show that, contrasting this hypothesis, μ substantially exceeds the drift barrier in diverse organisms. Random mutation accumulation (MA) in yeast frequently reduces μ, and deleting the newly discovered mutator gene PSP2 nearly halves μ. These results, along with a comparison between the MA and natural yeast strains, demonstrate that μ is maintained above the drift barrier by stabilizing selection. Similar comparisons show that the mutation spectrum such as the universal AT mutational bias is not intrinsic but has been selectively preserved. These findings blur the separation of mutation from selection as distinct evolutionary forces but open the door to alleviating mutagenesis in various organisms by genome editing.

Sign in / Sign up

Export Citation Format

Share Document