Selection Coefficient Calculator

A selection coefficient (s) measures the relative reduction in fitness of a genotype compared to the most fit genotype in the population. It ranges from 0 (no selection) to 1 (lethal), with s = 1 - W, where W is the relative fitness.

Relative fitness is calculated by dividing each genotype's absolute fitness by the highest fitness value among all genotypes. The most fit genotype has a relative fitness of 1.0, while others have values between 0 and 1.

The dominance coefficient (h) determines how the heterozygote fitness relates to the homozygotes. h = 0 means complete dominance, h = 0.5 means additive effects, and h = 1 means the recessive allele is completely recessive.

Natural selection can be directional (favoring one extreme), balancing (maintaining multiple alleles), or disruptive (favoring extremes over intermediates). The selection coefficient helps quantify the strength of these selective forces.

Selection changes allele frequencies each generation. Positive selection increases beneficial allele frequencies, while negative selection decreases harmful allele frequencies. The rate depends on the selection coefficient and dominance relationships.

Selection coefficients above 0.1 are generally considered strong, while those below 0.01 are weak. Most natural selection is relatively weak (s < 0.05), but even small coefficients can have significant evolutionary effects over many generations.

Yes, fitness values can exceed 1.0 when a genotype has higher survival or reproductive success than the reference. This commonly occurs with heterozygote advantage (overdominance) where the heterozygote is most fit.