1. What is Selection Coefficient?

Definition: The selection coefficient (s) measures the relative fitness difference between two genotypes or phenotypes in evolutionary biology.

Purpose: It quantifies the strength of natural selection acting on a particular trait or allele.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( s \) — Selection coefficient (dimensionless)
• \( f_{\text{new}} \) — Fitness of new genotype/phenotype
• \( f_{\text{old}} \) — Fitness of reference genotype/phenotype

Explanation: Positive values indicate advantageous traits, negative values indicate disadvantageous traits, and zero indicates neutral selection.

3. Interpretation of Results

Details:

• s > 0: The new trait is favored by selection
• s = 0: No selection difference
• s < 0: The new trait is selected against
• s = 1: Complete selection for the new trait
• s = -1: Complete selection against the new trait

4. Using the Calculator

Tips: Enter the fitness values for both genotypes/phenotypes. The reference (old) fitness must be greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: What units are used for fitness values?
A: Fitness is typically unitless, representing relative reproductive success (often scaled from 0 to 1).

Q2: What does a selection coefficient of 0.01 mean?
A: The new genotype has a 1% fitness advantage over the reference genotype.

Q3: Can the coefficient be greater than 1?
A: Yes, if the new fitness is more than double the old fitness, though such large values are rare in nature.

Q4: How is this different from relative fitness?
A: The selection coefficient specifically measures the difference in fitness relative to the reference.

Q5: What's a typical range for selection coefficients?
A: Most coefficients in nature range from -0.1 to 0.1, with strong selection being >0.1 or <-0.1.