Drift & Selection on rare alleles with weak selective advantage in finite populations
(N = 100, f(B0) = 0.005, W0 = W1 = 0.99, W2 = 1.0)
Trajectories
of a weakly advantageous (s = -0.01) mutant allele in multiple
populations (N = 100 @). From a single
copy of such an allele (initial f(B) = 1/200
= 0.005), almost all populations go to f(B) =
0.0 within 25 generations; two populations
remain polymorphic at 50 ~ 100 generation, and only one goes
to f(B) = 1, despite the selective advantage of B
in the BB genotype. Stochastic genetic drift in
a population of moderate size has a greater effect than does
weak directional deterministic selection. Note that s
> 1/2N.
Text material © 2021 by Steven M. Carr