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Selection coefficient Calculator

Measure of disadvantage relative to the fittest genotype.

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Selection Coefficient

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Overview

The selection coefficient quantifies the proportional reduction in the genetic contribution of a particular genotype to the next generation compared to a standard reference genotype. It measures the intensity of natural selection acting against a phenotype, where a higher value indicates a greater selective disadvantage.

Symbols

Variables

w = Relative Fitness, s = Selection Coefficient

Relative Fitness
Variable
Selection Coefficient
Variable

Apply it well

When To Use

When to use: Use this coefficient when modeling the rate of allele frequency changes within a population over time. It is essential in population genetics scenarios where you need to compare the reproductive success of different phenotypes against the most fit individual in the group.

Why it matters: This value allows biologists to predict how quickly beneficial traits will spread or deleterious traits will be eliminated from a gene pool. It is critical for understanding real-world phenomena like the development of antibiotic resistance in bacteria or the survival of endangered species in changing climates.

Avoid these traps

Common Mistakes

  • Mixing s and w.
  • Using percent instead of decimal.

One free problem

Practice Problem

In a study of bird beak shapes, a specific genotype is found to have a relative fitness (w) of 0.85 compared to the most successful phenotype. Calculate the selection coefficient (s) acting against this genotype.

Relative Fitness0.85

Solve for:

Hint: Subtract the given relative fitness from the maximum possible fitness value of 1.0.

The full worked solution stays in the interactive walkthrough.

References

Sources

  1. Hartl, D. L., & Clark, A. G. (2007). Principles of Population Genetics. Sinauer Associates.
  2. Freeman, S., & Herron, J. C. (2007). Evolutionary Analysis. Pearson Prentice Hall.
  3. Wikipedia: Selection coefficient
  4. Evolution by Douglas J. Futuyma, 3rd Edition
  5. Hartl, D. L., & Clark, A. G. Principles of Population Genetics. Sinauer Associates.
  6. Futuyma, D. J., & Kirkpatrick, M. Evolution. Sinauer Associates.
  7. Crow, J. F., & Kimura, M. An Introduction to Population Genetics Theory. Harper & Row.
  8. Standard curriculum — Population Genetics