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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).

What is Natural Selection?

What is Natural Selection?

Natural selection is an evolutionary process in which individuals with survival-promoting traits reproduce at higher rates. These favorable traits become more common within a population or species. Naturally selected traits initially arise via random genetic mutations. In order for selection to occur, there must be variation within a population, the trait controlling the variation must be heritable, and there must be an evolutionary advantage for variation in the trait.

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.

The Evidence for Evolution

The Evidence for Evolution

Genetic variations accumulating within populations over generations give rise to biological evolution. Evolutionary changes can result in the formation of novel varieties and entire new species. These changes are responsible for the diverse forms of life inhabiting the planet. The evidence for evolution suggests that all living organisms descended from common ancestors.

Frequency-dependent Selection

Frequency-dependent Selection

When the fitness of a trait is influenced by how common it is (i.e., its frequency) relative to different traits within a population, this is referred to as frequency-dependent selection. Frequency-dependent selection may occur between species or within a single species. This type of selection can either be positive—with more common phenotypes having higher fitness—or negative, with rarer phenotypes conferring increased fitness.

Speciation Rates

Speciation Rates

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Related Experiment Video

Updated: Mar 2, 2026

An Experimental and Bioinformatics Protocol for RNA-seq Analyses of Photoperiodic Diapause in the Asian Tiger Mosquito, Aedes albopictus

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Eco-Evolutionary Theory and Insect Outbreaks.

David J Páez, Vanja Dukic, Jonathan Dushoff

The American Naturalist

|May 18, 2017

Summary

This summary is machine-generated.

Eco-evolutionary dynamics explain insect population cycles. Field experiments with gypsy moth baculovirus confirmed heritable and costly reduced infection risk, validating models of host-pathogen cycles.

Keywords:

complex dynamics eco-evolutionary heritability host-pathogen trade-offs

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Area of Science:

Ecology
Evolutionary Biology
Population Dynamics

Background:

Eco-evolutionary theory posits that natural selection drives population cycles in consumer-resource interactions.
Empirical evidence supporting this theory in natural systems is scarce due to experimental limitations.
Insect-pathogen systems, like baculoviruses and gypsy moths, offer tractable models for testing these assumptions.

Purpose of the Study:

To experimentally test key assumptions of eco-evolutionary models for host-pathogen population cycles.
Specifically, to determine if reduced host infection risk is heritable and costly in gypsy moth baculovirus interactions.
To assess the utility of eco-evolutionary models in explaining forest insect outbreaks.

Main Methods:

Conducted field experiments using gypsy moth (Lymantria dispar) and its baculovirus pathogen.
Assessed the heritability of reduced host infection risk.
Quantified the fitness costs associated with reduced infection risk.

Main Results:

Confirmed that reduced gypsy moth infection risk is both heritable and associated with a fitness cost.
Incorporated empirically derived parameters into eco-evolutionary insect-outbreak models.
Observed that these eco-evolutionary models accurately replicated gypsy moth outbreak cycles in North America.

Conclusions:

Eco-evolutionary models provide a robust framework for understanding forest insect defoliator outbreaks.
The study validates the role of heritable and costly resistance in driving host-pathogen population dynamics.
Findings suggest eco-evolutionary dynamics are a general mechanism in forest insect outbreaks.