How do FST and QST differ in population genetics analysis?

• A. FST measures differentiation at neutral markers; QST measures differentiation of quantitative traits
• B. FST measures differentiation of quantitative traits; QST measures neutral markers
• C. FST assesses ecological divergence; QST assesses mutation rates
• D. FST and QST measure the same thing

Answer: (B)

The main idea is that these two statistics capture genetic differentiation in different kinds of variation. FST looks at allele frequencies at neutral genetic markers across populations. Because these markers are assumed not to be affected by selection, differences between populations mainly reflect genetic drift and gene flow. QST, on the other hand, measures how much populations differ in quantitative traits, which are shaped by additive genetic variation across many genes. It tells you how much of the observed trait divergence is due to genetics rather than environment.

So the correct way to describe them is that FST measures differentiation at neutral markers, while QST measures differentiation of quantitative traits. Comparing the two can hint at selection: if QST is greater than FST, trait divergence exceeds neutral divergence suggesting divergent selection; if QST is lower, it can indicate stabilizing selection or limited additive genetic variance.