Stochastic Competition — Extinction by Genetic Drift

Two species compete in a finite population. Even with equal fitness, neutral drift drives one to fixation. The Moran model gives fixation probability P₁ = x (fraction of species 1). Multiple independent realizations shown.

Population N

50

Species 1 fitness s

0.00 (neutral)

Realizations

10

Initial fraction x₀

0.50

N = —
Fixation prob P₁ = —
Expected fix time:
— gen
Fixed sp1: 0
Fixed sp2: 0
Extinct: 0