How does disruptive selection influence the population variance?

Disruptive selection plays a significant role in influencing population variance by enhancing it. This type of natural selection occurs when individuals at both extremes of a trait distribution have a selective advantage over individuals with intermediate traits. As a result, disruptive selection promotes the survival and reproduction of individuals that are either at one extreme or another, thus leading to an increased divergence in traits within the population.

As extreme phenotypes become more favorable in specific environments or contexts, the intermediate phenotypes may struggle to compete, causing their numbers to decrease. This selective pressure effectively separates the population into two distinct groups that exhibit different trait characteristics. Over time, this can lead to greater differences in phenotypes and, consequently, an increase in genetic variance within the population. The overall effect is a broadening of the distribution of traits, contributing to an enhanced variance rather than a reduction or elimination of variance.