Fig. 3

The frequency of the blindness allele (Q) in the surface population affects the level of selection (s) required to produce blind populations. The format of this figure follows Fig. 2: a shows when the blind allele becomes the majority allele; b shows when the blind phenotype becomes the majority phenotype; c shows when the blind allele becomes fixed; d shows when the blind phenotype becomes fixed. As Q increases, the amount of selection required to evolve blindness in the cave population decreases. A surface population with a high Q can be considered “pre-adapted” to the cave. The curves were calculated analytically with u=10⁻⁶ and h=0.5