Difference Between Disruptive Selection and Stabilizing Selection

The key difference between disruptive selection and stabilizing selection is that disruptive selection favours both extreme phenotypes while stabilizing selection favours average phenotypes in a population, eliminating both extremes.

Disruptive selection and stabilizing selection are two types of natural selection processes. Disruptive selection favours both extreme phenotypes over intermediate phenotype. Hence, it increases the genetic variance of the population. In contrast, stabilizing selection favours middle phenotypes against both extremes. Therefore, stabilizing selection decreases the genetic variance of the population.

CONTENTS

1. Overview and Key Difference
2. What is Disruptive Selection 
3. What is Stabilizing Selection
4. Similarities Between Disruptive Selection and Stabilizing Selection
5. Side by Side Comparison – Disruptive Selection vs Stabilizing Selection in Tabular Form
6. Summary

What is Disruptive Selection?

Disruptive selection, also known as diversifying selection, is the selection of both extreme traits over the middle non-extreme trait. This results in a two peaked curve. This can be explained based on the phenomenon of plant height and their respective pollinators. If there are separate pollinators for tall, short and medium plants and when the pollinators of the medium plant disappear, the population of plants will eventually shift towards the two extreme traits: short and tall.  This population is termed as a polymorphic population since there are more than one forms existing. The population becomes diverse as a result of disruptive selection.

What is Stabilizing Selection?

Stabilizing selection is a type of natural selection which favours the average or middle phenotypes in a population. In other words, stabilizing selection pushes a population towards the average or median while eliminating the two extreme phenotypes. The environment normally favours the average phenotype within a population. Stabilizing selection is the quantitative equivalent of balancing selection for a single gene trait.

For example, birth weight in human shows stabilizing selection against very small and very large birth weights. Another example is the body size of a species of a lizard belonging to genus Aristelliger. Small lizards and large lizards are eliminated, and the average size lizards are favoured by the natural selection. Stabilizing selection makes the population more uniform since natural selection works against the two extremes. Therefore, it reduces the genetic variation of the population.

What are the Similarities Between Disruptive Selection and Stabilizing Selection?

• Disruptive selection and stabilizing selection are two modes of natural selection.
• Both affect the distribution of phenotypes within a population.

What is the Difference Between Disruptive Selection and Stabilizing Selection?

Disruptive selection is a mode of natural selection which favours extreme values over intermediate values in a population. Stabilizing selection is a mode of natural selection which favours an average trait value over two extreme trait values. So, this is the key difference between disruptive selection and stabilizing selection. Disruptive selection increases the population’s genetic variance while stabilizing selection decreases the population’s genetic variance.

Below infographic tabulates more differences between disruptive selection and stabilizing selection.

Summary – Disruptive Selection vs Stabilizing Selection

Stabilizing selection is a type of natural selection that applies to a phenotypic trait. It favours average phenotypes in a population and eliminates both types of extreme phenotypes. Ultimately it makes a uniform population. As a result, the population’s genetic variance decreases. In contrast, disruptive selection is a type of natural selection which favours both extreme traits together. It increases the genetic variance of the population. Thus, this summarizes the difference between disruptive selection and stabilizing selection.

Reference:

1. “19.3B: Stabilizing, Directional, and Diversifying Selection.” Biology LibreTexts, Libretexts, 15 Aug. 2020, Available here.
2. “Disruptive Selection.” Biology Dictionary, 29 Apr. 2017, Available here.

Image Courtesy:

1. “Disruptive selection” By BoH – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Directional, Disruptive and Stabilizing Selections” By Ibbiologystudentone – Own work (CC BY-SA 4.0) via Commons Wikimedia