If the egg-to-adult survival rates of genotypes A 1 A 1 , A 1 A 2 , and A 2 A 2

Question

If the egg-to-adult survival rates of genotypes A1A1, A1A2, and A2A2 are 90 percent, 85 percent, and 75 percent, and their fecundities are 50, 55, and 70 eggs per female, respectively, what are the absolute fitnesses (W) of these genotypes? Using A1A1 as the fitness reference, what are the relative fitnesses (w)? If the frequency of the A2 allele is p = 0.5, what will be its frequency one generation later? What will be the allele frequency when the population reaches equilibrium (stops evolving)?

Explanation / Answer

Here fitness means how many new generation eggs is each egg posssible to produce; to get absolute fitness we have to multiply average fecundity to the probability of survival to adulthood.
Relative Fitness (w) is defined as the survival rate of a genotype / phenotype comparative to the maximum survival rate of another genotypes / phenotypes in the population. in this case A2A2 has more survival rate

45/52.5=0.86

in first scenario result shows directional selection for A2; A2 A2 has higher fitness than A1A2 and A1A2 has more fitness than A1A1.
In the second scenario 2, result shows disruptive selection,that enhances the probability of maintained genetic variation. here A1 has more absolute fitness then A2, get opposite from 1st.

in third scenario this is not changed with different fecundities, the survival rate still decreases advantage of A2 comparatively from first generation also increases advantage of A1 in second -- so likely still goes to A1 fixation, and perhaps faster.

SCENARIO 1 SCENARIO 2 annualized annualized egg-adult ave.adult absolute relative adults ave absolute relative survival fecundity fitness fitness generation2 fecundity fitness fitness A1A1 0.9 50 50*0.9=45

45/52.5=0.86

45*.9=40.5 70 2835 1 A1A2 0.85 55 55*0.85=46.75 46.75/52.5=0.89 39.74 65 2582.94 0.91 A2A2 0.75 70 0.75*70=52.5 52.5/52.5=1 39.38 55 2165.63 0.76 SCENARIO 3 annualized annualized egg-adult ave.adult absolute relative adults ave absolute relative survival fecundity fitness fitness generation2 fecundity fitness fitness A1A1 0.9 55 49.5 0.88 44.55 75 3341.25 1 A1A2 0.85 65 55.25 0.98 46.96 65 3052.56 0.91 A2A2 0.75 75 56.25 1 42.19 55 2320.31 0.69

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