Calculator Inputs
Choose a method, enter genotype information, and submit to calculate genotype-specific selection coefficients and allele frequency change.
Example data table
This example shows how the calculator behaves with direct genotype fitness values and an initial allele A frequency of 0.60.
| Example method | WAA | WAa | Waa | Reference | p0 | sAA | sAa | saa |
|---|---|---|---|---|---|---|---|---|
| Absolute fitness | 1.00 | 0.92 | 0.78 | Best genotype | 0.60 | 0.00 | 0.08 | 0.22 |
Formula used
Relative fitness
wi = Wi / Wref
Each genotype is scaled to the selected reference genotype or to the best genotype.
Selection coefficient
si = 1 - wi
A genotype with lower relative fitness has a larger positive selection coefficient.
Fitness from counts
Wi = Nafter / Nbefore
When counts are supplied, genotype fitness is estimated from survival or reproductive success.
Mean fitness and allele update
w̄ = p²wAA + 2pqwAa + q²waa
p′ = (p²wAA + pqwAa) / w̄
These equations project the allele A frequency over generations under viability selection.
How to use this calculator
- Select the input method that matches your data source.
- Choose the genotype used for relative scaling, or keep the best genotype.
- Enter genotype fitness values or counts before and after selection.
- Provide the starting allele A frequency and projection length.
- Submit the form to see genotype fitness, selection coefficients, and allele shifts.
- Use the export buttons to save a CSV summary or a PDF report.
FAQs
1. What does the selection coefficient mean?
It measures how much less fit a genotype is compared with the chosen reference. A value of 0 means equal fitness, while larger positive values indicate stronger selection against that genotype.
2. Why can one genotype have a negative selection coefficient?
That happens when you scale relative fitness to a reference genotype that is not the fittest. A genotype fitter than the chosen reference will produce a negative value for s.
3. When should I use counts instead of fitness values?
Use counts when you know genotype totals before and after selection, survival, or reproduction. The calculator converts those ratios into estimated absolute fitness values automatically.
4. What does the allele frequency projection assume?
The projection assumes viability selection using the entered genotype fitness values. It does not add mutation, migration, drift, assortative mating, or frequency-dependent selection unless you modify the model.
5. How should I interpret the dominance coefficient h?
The displayed h value describes where the heterozygote lies between the two homozygotes. Around 0 suggests dominance by AA, around 1 suggests dominance by aa, and around 0.5 suggests additivity.
6. Can I use relative fitness values greater than 1?
Yes. Relative values can exceed 1 if your chosen reference genotype is weaker than another genotype. The calculator rescales values consistently and still computes valid genotype-specific coefficients.
7. Does this tool work for diploid populations only?
This version is structured around the three diploid genotypes AA, Aa, and aa. Haploid, polyploid, or multi-allele systems would require an expanded model and additional equations.
8. What is the best reference choice?
Using the best genotype is common because it makes the fittest genotype equal to 1 and produces intuitive positive coefficients for less fit genotypes. Custom references are useful for comparison studies.