$$R = h^2 S$$

Equation 1 · Evolutionary Biology

Darwin's Finches: The Beak the Grants Measured for Forty Years

This equation states an equality: the expressions on both sides have the same value under the article’s assumptions.

Heritability is what turns a measured selection differential into a testable prediction, through the simplest quantitative-genetics identity in the field, the breeder’s equation: $R = h^2 S$. where S is the selection differential actually measured on the population in one generation, $h^2$ is the trait’s heritability, and R is the response: the amount the population’s mean should shift in the next generation, if the difference between survivors and non-survivors was genetic rather than purely environmental. Grant and Grant ran exactly this check on their own data, comparing the mean of a trait before a selection episode with the mean of the same trait in the following generation. The…

Meanings in this article

• $R$: the response: the amount the population’s mean should shift in the next generation, if the difference between survivors and non-survivors was genetic rather than purely environmental.
• $h^2$: the trait’s heritability.
• $S$: the selection differential actually measured on the population in one generation, $h^2$ is the trait’s heritability.

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