SELECTION vs DRIFT
Wright-Fisher
Population N:
200
Selection s:
0.01
Init freq p₀:
0.1
Trajectories:
20
Speed:
3
Phase diagram
N range:
10–500
New Run
Pause
Fixed:
0
Lost:
0
Running:
0
Wright-Fisher model: binomial sampling each generation. Ns >> 1: selection dominates. Ns << 1: drift dominates. Fixation probability = (1-e^{-2sp₀})/(1-e^{-2sN}) ≈ 2s for rare beneficial allele.