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Related Concept Videos

Frequency-dependent Selection01:21

Frequency-dependent Selection

23.0K
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.
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Types of Selection01:46

Types of Selection

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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...
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Mutation, Gene Flow, and Genetic Drift01:09

Mutation, Gene Flow, and Genetic Drift

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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).
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Genetic Drift03:33

Genetic Drift

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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.
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Hardy-Weinberg Principle01:49

Hardy-Weinberg Principle

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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.
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Gene Flow02:39

Gene Flow

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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

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Following the Dynamics of Structural Variants in Experimentally Evolved Populations
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Negative frequency-dependent selection maintains coexisting genotypes during fluctuating selection.

Caroline B Turner1, Sean W Buskirk2, Katrina B Harris1

  • 1Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, PA, USA.

Molecular Ecology
|November 15, 2019
PubMed
Summary
This summary is machine-generated.

Bacterial adaptation to fluctuating environments differs genetically from constant environments. Fluctuating selection on biofilm and planktonic growth in Burkholderia cenocepacia maintained coexisting genotypes via frequency-dependent selection.

Keywords:
adaptationbacteriaexperimental evolutionpopulation ecology

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Area of Science:

  • Evolutionary biology
  • Microbial genetics

Background:

  • Natural environments are dynamic, leading to fluctuating selection pressures.
  • Understanding genetic adaptation to fluctuating versus constant environments is crucial.
  • Bacteria face varying selection for planktonic or biofilm growth.

Purpose of the Study:

  • To investigate the genetic basis of adaptation in fluctuating environments.
  • To compare evolutionary dynamics under constant versus fluctuating selection.
  • To examine adaptation in Burkholderia cenocepacia under different growth selection regimes.

Main Methods:

  • Conducted an evolution experiment with Burkholderia cenocepacia populations.
  • Applied constant selection for biofilm or planktonic growth.
  • Applied weekly fluctuating selection between biofilm and planktonic growth.

Main Results:

  • Fluctuating environment populations shared genetic targets with constant biofilm selection but differed from constant planktonic selection.
  • Mutations in wspA and rpfR genes were prevalent in the fluctuating environment.
  • Coexistence of wspA and rpfR genotypes was maintained by negative frequency-dependent selection.

Conclusions:

  • Fluctuating environments can maintain coexisting genotypes, contrary to narrow predictions.
  • Frequency-dependent interactions provide a mechanism for genotype coexistence in fluctuating environments.
  • Bacterial adaptation to fluctuating environments involves unique genetic dynamics, particularly in regulating growth modes.