If two subpopulations have Fst ≈ 0.2, what does this imply?

• A. No differentiation.
• B. Complete differentiation.
• C. High differentiation with strong isolation.
• D. Moderate differentiation; some gene flow but substantial genetic structure remains.

Answer: (D)

Fst measures how much genetic variation is due to differences between subpopulations. An Fst around 0.2 means roughly 20% of the total genetic variation is between the populations, with about 80% within them. This shows noticeable differentiation, but not complete separation. There is some gene flow between the groups, which keeps them from being completely distinct, yet enough structure remains to show clear differences. So the situation reflects moderate differentiation with ongoing gene flow. Values near 0 would mean no differentiation, while values near 1 would indicate almost complete separation.