Question

3. Suppose a species has two generations per year, that adult survival rates of genotypes A,A, AAy and A2A2 are identical, and that the fecundity values are 50, 55, and 70 in the spring genera- tion and 70, 65, and 55 in the fall generation, respectively. Will polymorphism persist, or will one allele become fixed if fecundity values are unchanged for many years? What if the fecun- dity values are 55, 65, 75 in the spring and 75, 65, 55 in the fall?

Answer 1

In the long run, the A₂ allele will get fixed and the polymorphism would not remain.

The reason is that A₂ has a high fecundity value in spring, which is more than that of A₁ (70-50=20 units).

And while A₁ has such high fecundity in fall, it is not enough to compensate the difference(70-55 =15 units).

Hence, A₂ will get fixed.

However, the same will not happen in the second case as, the fecundity values for both the alleles are symmetrical now for spring and fall. That is, one's high fecundity in spring is exactly compensated by the other's high fecundity in fall.

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