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Related Concept Videos

Frequency-dependent Selection01:21

Frequency-dependent Selection

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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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Organisms that are well-adapted to their environment are more likely to survive and reproduce. However, natural selection does not lead to perfectly adapted organisms. Several factors constrain natural 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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What is Natural Selection?01:32

What is Natural Selection?

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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.
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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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Natural Selection and Adaptation01:15

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Natural selection, a fundamental concept in evolutionary biology, is the mechanism by which evolution is driven, favoring organisms that are best adapted to their environments. This process enhances their chances of survival and reproduction. Adaptation, a key outcome of this process, involves genetic modifications that optimize an organism's functionality under specific environmental challenges, such as extreme cold or thinner air at high altitudes.
Beyond physical adaptations,...
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Density-dependent natural selection mediates harvest-induced trait changes.

Alix Bouffet-Halle1, Jacques Mériguet2,3, David Carmignac1

  • 1Sorbonne Université, Université Paris Diderot, UPEC, CNRS, INRA, IRD, Institut d'Ecologie et des Sciences de l'Environnement de Paris (iEES-Paris), Paris, F-75252, France.

Ecology Letters
|January 29, 2021
PubMed
Summary
This summary is machine-generated.

Harvesting medaka fish caused life-history changes, but not due to direct selection against large size. Instead, relaxation of natural selection in unharvested populations favored larger body size via density-dependent selection.

Keywords:
Adaptive landscapesasymmetric competitionbody sizecannibalismeco-evolutionary feedback loopsenergy allocation rulesfisheriesglobal changeharvesting yieldslife-history change

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Area of Science:

  • Evolutionary biology
  • Ecology
  • Fisheries science

Background:

  • Size-selective harvesting is often assumed to drive rapid life-history evolution by directly selecting against large body size.
  • However, indirect effects, such as the relaxation of natural selection due to harvest-induced density changes, can also cause similar evolutionary responses.

Discussion:

  • This study investigated the drivers of life-history divergence in medaka fish (Oryzias latipes) under harvesting.
  • Replicated pond populations revealed density-dependent selection favoring larger body size at high densities in unharvested populations.
  • Harvesting directly selected against large body size and reduced population densities, leading to divergent life-history trajectories.

Key Insights:

  • Life-history divergence in harvested medaka was primarily driven by density-dependent natural selection in unharvested populations, not direct harvest selection for smaller size.
  • Unharvested medaka exhibited slower growth and earlier maturation compared to harvested populations, contrary to predictions based solely on direct selection.
  • The findings highlight the critical role of indirect ecological effects, specifically density-dependent selection, in shaping evolutionary responses to harvesting.

Outlook:

  • Understanding the interplay between direct and indirect selection is crucial for effective fisheries management and conservation.
  • Further research should explore the generality of density-dependent selection in mediating evolutionary responses to exploitation across different species and ecosystems.
  • Investigating the genetic basis of density-dependent selection can provide deeper insights into the mechanisms of rapid adaptation.