Estimating fitness from data taken before and after selection within the same generation

Number of individuals with each genotype

(obtained by counting)

AA Aa aa

Before selection 4,000 5,100 2,300

After selection 3,800 4,200 1,200

Survival Rate

3,800/4,000 4,200/5,100 1,200/2,300

= .95 = .82 = .52

w = Relative fitness= .95/.95 = 1.0 .82/.95 = .86 .52/.95 = .55

s = Selection coefficient = 0 = .14 = .45

w = 1 - s

s = 1 - w

41F