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Mutation, Gene Flow, and Genetic Drift

Mutation, Gene Flow, and Genetic Drift

In a population that is not at Hardy-Weinberg equilibrium, the frequency of alleles changes over time. Therefore, any deviations from the five conditions of Hardy-Weinberg equilibrium can alter the genetic variation of a given population. Conditions that change the genetic variability of a population include mutations, natural selection, non-random mating, gene flow, and genetic drift (small population size).

Genetic Drift

Genetic Drift

Natural selection—probably the most well-known evolutionary mechanism—increases the prevalence of traits that enhance survival and reproduction. However, evolution does not merely propagate favorable traits, nor does it always benefit populations.

Types of Selection

Types of Selection

Natural selection influences the frequencies of particular alleles and phenotypes within populations in several different ways. Primarily, natural selection can be directional, stabilizing, or disruptive. Directional selection favors one extreme trait and shifts the population towards that phenotype while selecting against individuals displaying alternate traits. Stabilizing selection favors an intermediate trait with a narrow range of variation. Deviation from the optimal phenotype towards an...

Hardy-Weinberg Principle

Hardy-Weinberg Principle

Diploid organisms have two alleles of each gene, one from each parent, in their somatic cells. Therefore, each individual contributes two alleles to the gene pool of the population. The gene pool of a population is the sum of every allele of all genes within that population and has some degree of variation. Genetic variation is typically expressed as a relative frequency, which is the percentage of the total population that has a given allele, genotype or phenotype.

Genetics of Speciation

Genetics of Speciation

Speciation is the evolutionary process resulting in the formation of new, distinct species—groups of reproductively isolated populations.

Gene Flow

Gene Flow

Gene flow is the transfer of genes among populations, resulting from either the dispersal of gametes or from the migration of individuals.

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Related Experiment Video

Updated: Jul 9, 2025

Following the Dynamics of Structural Variants in Experimentally Evolved Populations

Following the Dynamics of Structural Variants in Experimentally Evolved Populations

Published on: February 3, 2023

Evolutionary dynamics of mutants that modify population structure.

Josef Tkadlec^1,2, Kamran Kaveh³, Krishnendu Chatterjee⁴

¹Department of Mathematics, Harvard University, Cambridge, MA 02138, USA.

Journal of the Royal Society, Interface

|November 28, 2023

Summary

This summary is machine-generated.

Natural selection can be influenced by population structure, not just reproductive rates. Denser dispersal networks generally increase a mutant

Keywords:

Moran process evolutionary graph theory fixation probability spatial structure

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Area of Science:

Evolutionary biology
Population genetics
Mathematical modeling

Background:

Natural selection typically examines mutants with differing reproductive rates but identical population structures.
Understanding how population structure impacts selection is crucial for evolutionary dynamics.

Purpose of the Study:

To investigate the effects of varying population structures on natural selection when mutants share the same reproductive rate.
To analyze how graph-defined dispersal patterns influence mutant fixation probabilities.

Main Methods:

Modeling population structure using dispersal graphs.
Analyzing mutant fixation probabilities on different graph structures (complete graphs, island models, lattices).
Comparing the impact of structural differences to fitness differences.

Main Results:

Densely connected dispersal graphs tend to increase invader fixation probability.
Removing edges from complete dispersal graphs reduces fixation probability.
Connectivity effects vary across different population structures like island models and lattices.

Conclusions:

Population structure, defined by dispersal graphs, significantly modulates natural selection.
The relationship between dispersal network density and fixation probability is complex and context-dependent.
Structural differences can have selection effects comparable to fitness differences in large populations.