Question

All else being equal, which one of the following population sizes (𝑁) and migration rates (𝑚) would result in the most genetic differentiation between populations (𝐹𝑠𝑡)? Note that 𝐹𝑠𝑡 is computed as 𝐹𝑠t=1/4𝑁𝑚+1

• A. 𝑁 = 500, 𝑚 = 1
• B. 𝑁 = 200, 𝑚 = 200
• C. 𝑁 = 40, 𝑚 = 10
• D. 𝑁 = 40, 𝑚 = 1

Hint:

When interpreting bar plots with treatments, compare each bar directly to the relevant comparator(s); if the question hinges on “both,” each of the two comparisons must individually satisfy the condition.

Answer 1

The Correct Option is D

Step 1: Interpret the formula.
\(F_{st}=\dfrac{1}{4Nm+1}\) \(\Rightarrow\) larger \(F_{st}\) occurs when \(4Nm+1\) is \emph{smallest}, i.e., minimize \(Nm\).

Step 2: Compute \(Nm\) for each option.
(A) \(Nm=500\times 1=500\Rightarrow F_{st}\approx \frac{1}{2001}\).
(B) \(Nm=200\times 200=40000\Rightarrow F_{st}\approx \frac{1}{160001}\).
(C) \(Nm=40\times 10=400\Rightarrow F_{st}\approx \frac{1}{1601}\).
(D) \(Nm=40\times 1=40\Rightarrow F_{st}=\frac{1}{161}\) (largest among options). Final Answer:\quad \(\boxed{\text{(D) }N=40,\; m=1}\)