Natural Selection Rate Calculator
Calculate selection coefficient from allele frequency change over generations. Quantify how fast natural selection drives allele frequency change using the log-odds method.
🧬 Evolution📐 s = log-odds(p1/q1) - log-odds(p0/q0) / generations🧬 Biology
Initial allele frequency p0
Final frequency p1
Number of generations
Please enter valid values.
Formula & Reference
| Variable | Symbol | Formula | Units |
|---|---|---|---|
| Natural Selection Rate Calculator | — | s = log-odds(p1/q1) - log-odds(p0/q0) / generations | per generation |
Step-by-Step Examples
Example 1
Industrial Melanism
Dark moth allele: p0=0.01 to p1=0.95 in 50 generations.
- s = [log(0.95/0.05)-log(0.01/0.99)]/50 = 0.151
- Strong directional selection
- ~7 generations to double in frequency
✓ s = 0.15 — strong positive selection
Example 2
Drug Resistance
Resistance allele from p0=0.001 to p1=0.5 in 50 bacterial generations.
- s ≈ 0.12 per generation
- Rapid spread under antibiotic pressure
- ~6 generations to double
✓ s ≈ 0.12, resistance spreads fast
Example 3
Weak Selection
Allele from 0.20 to 0.18 in 10 generations.
- s ≈ -0.012 (weakly deleterious)
- Takes 100+ gen to be eliminated
- Drift may dominate at small Ne
✓ s ≈ -0.012, weak negative selection
Real-World Applications
Evolutionary Biology
Compare selection intensity across populations and loci.
Antibiotic Resistance
Predict how fast resistance alleles spread.
Drug Development
Selection coefficient informs persistence of resistance mutations.
Population Genetics
Key parameter for allele frequency trajectory models.
Common Mistakes to Avoid
⚠️
Ignoring drift effects
Small Ne: drift matters as much as selection. |s| must >> 1/(2Ne) to overcome drift.
⚠️
Assuming constant environment
s changes with environment; historical estimates may not predict future.
⚠️
Not accounting for dominance
Selection acts on phenotype; dominance modifies effective s for recessives.
Frequently Asked Questions
What is selection coefficient? ▾
s = relative fitness difference between genotypes. s=0.1 means 10% more offspring than average.
What is strong vs weak selection? ▾
Strong: s > 0.01. Weak: s < 0.001. Drift dominates when |s| < 1/(2Ne).
How fast does selection act? ▾
With s=0.1, p goes from 0.01 to 0.50 in ~130 generations.
What is balanced selection? ▾
Heterozygote advantage maintains both alleles (e.g. sickle cell). No allele eliminated.
Can selection be detected from sequence data? ▾
Yes. FST outlier tests, Tajima's D, and dN/dS ratios detect selection signatures.