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Related Concept Videos

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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Mate Choice01:20

Mate Choice

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Mate choice—the decision about whom to mate with—is a type of natural selection, since animals must reproduce to pass down their genes. Mate choice is also called intersexual selection because the behavior occurs between the sexes.
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Epistasis01:39

Epistasis

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In addition to multiple alleles at the same locus influencing traits, numerous genes or alleles at different locations may interact and influence phenotypes in a phenomenon called epistasis. For example, rabbit fur can be black or brown depending on whether the animal is homozygous dominant or heterozygous at a TYRP1 locus. However, if the rabbit is also homozygous recessive at a locus on the tyrosinase gene (TYR), it will have an unshaded coat that appears white, regardless of its TYRP1...
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Predators consume prey for energy. Predators that acquire prey and prey that avoid predation both increase their chances of survival and reproduction (i.e., fitness). Routine predator-prey interactions elicit mutual adaptations that improve predator offenses, such as claws, teeth, and speed, as well as prey defenses, including crypsis, aposematism, and mimicry. Thus, predator-prey interactions resemble an evolutionary arms race.
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Background and Environment Affect Phenotype02:27

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Although the genetic makeup of an organism plays a major role in determining the phenotype, there are also several environmental factors, such as temperature, oxygen availability, presence of mutagens, that can alter an organism’s phenotype.
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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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Related Experiment Video

Updated: Nov 14, 2025

Manipulation of Color Patterns in Jumping Spiders for Use in Behavioral Experiments
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Close encounters of the three morphs: Does color affect aggression in a polymorphic lizard?

Stefano Scali1, Marco Mangiacotti2, Roberto Sacchi2

  • 1Department of Vertebrate Zoology, Natural History Museum of Milan, Milano, Italy.

Aggressive Behavior
|March 8, 2021
PubMed
Summary

Aggressive interactions between color morphs in lizards are more common when individuals encounter similar colors. This bias in aggression helps maintain color diversity and may contribute to the formation of new species.

Keywords:
Podarcis muralisalternative strategiescolor polymorphismhomomorphic aggressionlacertid lizardmirror testmorph spatial distribution

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Area of Science:

  • Evolutionary Biology
  • Behavioral Ecology
  • Genetics

Background:

  • Color polymorphism, genetically controlled, influences speciation and extinction rates.
  • Color badges serve as signals in intraspecific communication, potentially reducing conflicts.
  • Aggressive interactions among color morphs can maintain polymorphism and affect spatial distribution.

Purpose of the Study:

  • To assess if aggression varies among color morphs in the polymorphic lizard, Podarcis muralis.
  • To test hypotheses of heteromorphic versus homomorphic aggression.
  • To link experimental findings with spatial distribution patterns in a wild population.

Main Methods:

  • Laboratory mirror tests were conducted after manipulating lizard coloration.
  • Analysis of the spatial distribution of morphs in a wild population was performed.
  • Aggression levels were compared between homomorphic (same morph) and heteromorphic (different morph) contests.

Main Results:

  • Experiments confirmed that aggression is more frequent during homomorphic contests than heteromorphic contests.
  • The spatial distribution analysis supported the experimental findings.
  • A bias in aggression, favoring rarer morphs, was observed.

Conclusions:

  • Minimizing risks and costs through alternative behavioral strategies can facilitate phenotype coexistence and reduce competition.
  • A bias in aggression, disadvantaging common morphs and benefiting rarer ones, acts as a negative-frequency-dependent process.
  • This process stabilizes polymorphism and may contribute to sympatric speciation.