Difference Between Founder Effect and Bottleneck Effect

The key difference between founder effect and bottleneck effect is that the founder effect occurs when a small group in a population splinters off from the original population and forms a new one, while the bottleneck effect occurs when the population contracts significantly into a smaller size due to natural disasters such as earthquakes, floods and fires.

Genetic drift is a phenomenon which is much more likely to occur in small populations and more unlikely to occur in large populations. Basically, it occurs due to random changes in allele frequencies, which could lead to the disappearance of some genes from small populations. Ultimately genetic drift causes less genetic diversity and variation in populations. it also causes the disappearance of some gene variants completely from the populations. Moreover, it can cause some rare alleles to become more frequent than before and even fixed. There are two types of genetic drift as the bottleneck effect and founder effect. They cause extreme reductions in populations.

CONTENTS

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

What is Founder Effect?

Founder effect is one of the events of genetic drift that takes place due to colonization. It occurs when a small group splits off from the main population to establish a colony.

Figure 01: Founder Effect

When breaking off from the original population, it may contain a different allele frequency than the original population. Thus, the new colony does not represent the full genetic diversity of the original population. Some variants may be completely absent in the established colony.

What is Bottleneck Effect?

Bottleneck effect is the second extreme phenomenon which causes genetic drift in small populations. In this phenomenon, due to natural disasters, population contracts into small size. Most of the individuals of the population die due to the natural disaster, causing loss of genetic variation within the population. Then the breeding occurs only between the remaining individuals, making them more abundant in the population. Eventually, it leads to the sharp lowering of the gene pool of the population.

Figure 02: Bottleneck Effect

Moreover, it is a disadvantage to have a narrow genetic diversity in the population. It may not be helpful when facing environmental changes and diseases.

What are the Similarities Between Founder Effect and Bottleneck Effect?

• Founder effect and bottle neck effect are extreme examples of genetic drift.
• They are more likely to occur in small populations.
• Both change allele frequencies by chance.
• They reduce genetic diversity and can lead to speciation.
• Both increase the probability of inbreeding.
• Some alleles completely disappear from the populations due to both phenomena.
• They can cause the loss of a beneficial allele or fixation of a harmful allele in a population.
• However, both are evolutionary important.

What is the Difference Between Founder Effect and Bottleneck Effect?

Founder effect arises due to the separation of a small group of individuals from a larger population to form a colony. Meanwhile, the bottleneck effect arises due to the contraction of the population into a small size as a result of a natural disaster killing most of the individuals in the population. So, this is the key difference between founder effect and bottleneck effect.

Below infographic summarizes the difference between founder effect and bottleneck effect.

Summary – Founder Effect vs Bottleneck Effect

Genetic drift is a mechanism of evolution in which allele frequencies of a population randomly change over generations. It occurs via two main ways: founder effect and bottleneck effect. The founder effect is an example of genetic drift in which a small group breaks off from the main population to establish a colony. Meanwhile, the bottleneck effect takes place when the population contracts into a small size due to a natural disaster and killing most of the individuals in the population. This is the key difference between founder effect and bottleneck effect. Both founder effect and bottleneck effect sharply reduce the gene pool of the population. Thus, both reduce the genetic diversity in a population.

Reference:

1. “Genetic Drift.” Khan Academy, Khan Academy, Available here.
2. “Bottleneck Effect: Definition & Example Video.” Study.com, Study.com, Available here.

Image Courtesy:

1. “Founder effect Illustration” By Tsaneda – Source: Founder_effect.jpg at wikieducatorIllustration is modeled on “Genetic Drift.” Boundless Biology. Boundless, 21 Jan. 2015. Retrieved 13 May. 2015 (CC BY 3.0) via Commons Wikimedia
2. “Bottleneck effect Figure 19 02 03” By OpenStax, Rice University – Textbook content produced by OpenStax, Rice University. (CC BY 4.0) via Commons Wikimedia

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