Difference Between Assortative and Disassortative Mating

The key difference between assortative and disassortative mating is that, in assortative mating, the mating occurs between phenotypically similar organisms while in disassortative mating, the mating occurs between two organisms that are phenotypically different.

In population genetics, mating is an important phenomenon for the survival of a particular species. The probability of mating is decided on the Hardy Weinberg equation. However, assortative mating follows the Hardy Weinberg equilibrium, while disassortative mating does not follow this equilibrium.

CONTENTS

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

What is Assortative Mating?

Assortative mating is a type of mating where the mating pair is similar in their phenotypes. This phenomenon is also referred to as the positive assortative mating or homogamy. Therefore, this type of mating is not a random mating type. During assortative mating, organisms with similar phenotypes in colour, pigmentation and body size mate with each other. Furthermore, the probability of assortative mating also increases with genetic compatibility. Also, this concept belongs to population genetics in the field of genetics.

There are different hypotheses that explain the phenomenon of assortative mating. Intrasexual competition is one of the main contributing factors to assortative mating; for example, there can be several males competing for the large female mate. Furthermore, social competition can also give rise to assortative mating. This will allow different organisms with similar traits to mate among each other. Competitive scenarios will, therefore, give rise to assortative mating by proximity rather than by choice.

What is Disassortative Mating?

Disassortative mating is also called the negative assortative mating or heterogamy. This mating enables the mating between two organisms with differences in their phenotypes. Thus, the genetic dissimilarity is also high between the two organisms. However, this method of mating is less common than positive mating or assortative mating. According to population genetics, this method of mating deviates from the Hardy Weinberg principle.

Furthermore, this method of mating reduces competition between organisms. However, there is less opportunity for this type of mating to take place. This form of mating is more random and not pre-determined. The organisms undergoing disassortative mating may have significantly different traits in their colour, pigmentation and their body size.

What are the Similarities Between Assortative and Disassortative Mating?

• Both mating types may result in fertile offspring.
• They may occur randomly; however assortative mating has a low rate of random occurrences.

What is the Difference Between Assortative and Disassortative Mating?

The key difference between assortative and disassortative mating depends on the phenotype similarity between the organisms in the mating relationship. Thus, in an assortative relationship, the organisms involved in mating have high phenotypic similarity while in a disassortative relationship, the organisms involved in mating have a low phenotypic similarity. In addition, the Hardy Weinberg equation is satisfied in an assortative mating pattern while it is not satisfied in a disassortative mating pattern.

The below infographic summarizes the difference between assortative and disassortative mating.

Summary – Assortative vs Disassortative Mating

Assortative mating and disassortative mating are two phenomena that result in the mating of organisms in a species. Assortative mating results from the mating between two organisms showing similar phenotypes. However, disassortative mating results from the mating between two organisms showing dissimilar phenotypes. Due to this difference, they also behave differently in the way in which they follow the Hardy Weinberg equilibrium. There is more random mating taking place in disassortative mating and less randomness in assortative mating. So, this is the summary of the difference between assortative and disassortative mating.

Reference:

1. “Assortative Mating and Disassortative Mating.” SpringerLink, Springer, Dordrecht, 1 Jan. 1970, Available here.

Image Courtesy:

1. “Scarlet lily beetle lilioceris lilii” By Charles J Sharp – Own work (CC BY-SA 3.0) via Commons Wikimedia