Survival of the Quasispecies

fitness

sp. A

3.

qsp. B+B'

2.8

other

1.

mutation

rate

evolve

time

This Demonstration illustrates that if the mutation rate is in a certain range, natural selection selects a quasispecies (B+B') of slightly lower individual fitnesses over an individual (A) of higher fitness. This idealized genome has length four; a genotype is specified by a "word" of four base pairs of type "0" or "1" (compare the four types, A, T, C, G in DNA); a point mutation interchanges a "0" and "1". The 16 genotypes are shown in a 4×4 grid; the

x

and

y

coordinates are given by the first two and the last two base pairs, and the

z

coordinate is the relative population of the genotype.