Properties of Stabilizing Selection

Stabilizing selection is a type of natural selection that favors the average phenotype in a population, resulting in a decrease in phenotypic variation over time. It operates in a constant environment where the selective pressures remain relatively stable. Here are the properties of stabilizing selection:

a) Operates in a constant environment:
Stabilizing selection is characterized by the preservation of the intermediate phenotype and the reduction of phenotypic variation in a population. It occurs when the environment remains relatively constant and favors the average phenotype. In such an environment, extreme phenotypes are selected against, leading to the maintenance of the intermediate phenotype. This is because the average phenotype is well-adapted to the prevailing conditions and provides a fitness advantage.

b) Mean value changes:
Contrary to the statement, stabilizing selection does not result in a change in the mean value of a trait. Instead, it acts to maintain the average phenotype and reduce the occurrence of extreme phenotypes. The mean value of the trait remains relatively constant over time, as the selection pressure favors individuals with traits close to the average.

c) Peak gets lower and wider:
Again, this statement is incorrect. Stabilizing selection does not cause the peak of the trait distribution to change. Instead, it narrows the distribution by reducing the occurrence of extreme phenotypes. As a result, the peak of the distribution remains in the same position, but the overall distribution becomes narrower.

d) Favors the complex phenotype:
The statement is incorrect. Stabilizing selection does not favor complex phenotypes. Instead, it favors the intermediate phenotype by selecting against extreme phenotypes. The complex phenotype may have a higher variation and may not provide a fitness advantage in a stable environment. Therefore, stabilizing selection acts to maintain the average phenotype rather than favoring complex phenotypes.

In summary, the correct property of stabilizing selection is that it operates in a constant environment. It does not cause a change in the mean value of a trait, nor does it result in a lower and wider peak or favor complex phenotypes. Stabilizing selection acts to preserve the average phenotype and reduce phenotypic variation in a population.