Related Experiment Video
Updated: Jun 19, 2026
15:00
Daily Transfers, Archiving Populations, and Measuring Fitness in the Long-Term Evolution Experiment with Escherichia coli
Published on: August 18, 2023
Evolution with stochastic fitness and stochastic migration.
Sean H Rice1, Anthony Papadopoulos
1Department of Biological Sciences, Texas Tech University, Lubbock, Texas, USA. sean.h.rice@ttu.edu
Plos One
|October 10, 2009
Summary
Migration
Area of Science:
- Evolutionary biology
- Population genetics
- Mathematical modeling
Background:
- Migration is crucial for evolution, affecting adaptation, speciation, and genetic variation.
- Migration is a stochastic process, yet existing models rely on simplifying assumptions.
- A general, exact mathematical description of evolution with migration is lacking.
Purpose of the Study:
- To develop a general and exact mathematical description of evolution incorporating migration.
- To investigate the impact of migration variance on evolutionary processes.
- To explore the complex interactions between selection and migration.
Main Methods:
- Derived an exact equation for directional evolution in open populations, a stochastic Price equation with migration.
- Analyzed the effect of migration rate variance on the relative impact of migration versus selection.
- Developed an equation for the effective migration rate.
Main Results:
- Increasing migration rate variance reduces migration's impact relative to selection, correcting biases in simpler models.
- Selection and migration interact complexly; strategies with high fitness and low migration can increase in frequency.
- The entire distribution of migration rates, not just means, determines migration's evolutionary role.
Conclusions:
- Evolutionary outcomes depend on the full distribution of migration rates, not just average values.
- Stochastic migration and selection interactions reveal evolutionary dynamics missed by deterministic theories.
- A new effective migration rate equation allows incorporating stochastic processes into simpler models.
Related Concept Videos
03:33Genetic 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.Life is not fair. A deer grazing contentedly in a field can have her meal cut tragically short by a bolt of lightning. If the doomed doe is one of only three in the population, 1/3 of the population’s gene pool is lost. Random events like this can...
01:09Mutation, 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).Mechanisms of Genetic VariationThe original sources of genetic variation are mutations,...
02:39Gene Flow
Gene flow is the transfer of genes among populations, resulting from either the dispersal of gametes or from the migration of individuals.
02:16Genetics of Speciation
Speciation is the evolutionary process resulting in the formation of new, distinct species—groups of reproductively isolated populations.The genetics of speciation involves the different traits or isolating mechanisms preventing gene exchange, leading to reproductive isolation. Reproductive isolation can be due to reproductive barriers that have effects either before or after the formation of a zygote. Pre-zygotic mechanisms prevent fertilization from occurring, and post-zygotic mechanisms...
01:24Evolution of New Traits in Microbes
Microorganisms evolve rapidly due to their large population sizes and short generation times, often exhibiting measurable changes within days under laboratory conditions. Natural selection acts on standing genetic variation, enabling the retention and amplification of beneficial traits that confer fitness advantages in changing environments.Adaptive Pigment Regulation in RhodobacterIn Rhodobacter, a genus of purple non-sulfur bacteria, light-harvesting pigments such as bacteriochlorophyll and...
01:07Speciation Rates
Speciation can proceed at markedly different rates, and evolutionary biologists commonly describe these differences through the models of gradualism and punctuated equilibrium. Both patterns explain how new species arise, but they differ in the tempo and continuity of evolutionary change. In both cases, evolutionary change arises from heritable variation within populations, with natural selection often shaping traits that improve survival and reproduction under specific environmental conditions.