Which type of selection favors extreme variations over moderate ones?

Disruptive selection is a type of natural selection that favors the extreme variations of traits within a population. This form of selection occurs when environmental conditions are such that individuals with traits at both ends of the spectrum have a better chance of survival and reproduction than those with intermediate traits. In other words, if individuals with extreme phenotypes are more successful in thriving and reproducing in a given environment, their traits become more frequent in the population over generations.

A classic example of disruptive selection can be seen in certain species of African seedcracker birds, where individuals with either very large or very small beaks are favored because they can efficiently crack different types of seeds. Intermediate beaks result in less efficient feeding, making those individuals less likely to survive and reproduce. Thus, the population may evolve to show two distinct phenotypic groups rather than clustering around a single average trait. This contrasts with other forms of selection such as stabilizing selection, which favors intermediate traits, or directional selection, which favors one extreme over the other.