Difference Between Hybridization and Introgression

Key Difference – Hybridization vs Introgression
 

Genetic extinction is a popular concept that comes under evolution. Genetic extinction explains how the introduction of subspecies and crossing over has resulted in the extinction of certain genes or alleles from a population. Hybridization and Introgression are two modes where genetic extinction could take place in both fauna and flora. Hybridization is referred to a process where there is interbreeding between species of two genetically distinct populations or species. Introgression is a genetic crossover that takes place between the species of the same population via a backcross to one or both of the parent species. The key difference between Hybridization and Introgression is the type of genetic crossover. During hybridization, the breeding takes place between genetically distinct populations whereas, in Introgression, the crossover takes place between species of the same population.

CONTENTS

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

What is Hybridization?

Hybridization is defined as the process of interbreeding between individuals of two distinct populations. Hybridization can be a natural process or can be induced under in vitro conditions. The resulting organism following the hybridization is referred to as a Hybrid.

Natural hybridization has been a popular breeding technique used over the past few decades. There are different types of hybridization techniques used in breeding; Single cross-hybridization, Double cross-hybridization, Triple cross-hybridization, Three-way cross-hybridization and Top cross-hybridization, etc. Single cross hybrids are formed between two breeding organisms. They can either be resulted in homozygous or heterozygous dominant organisms. The resulting F1 generation is phenotypically homogenous.

Double cross hybrids are produced by crossing two F1 generation organisms. Three-way cross hybrids are produced by the cross between the inbred organism and the F1 organism. Triple cross hybrids are the resultants of a cross between the F1 hybrid and the three-way cross hybrids. The final type; top cross hybrids are the resultants of a cross between the pure-bred male and the lower quality female. Genetic hybridization is another form of hybridization that results in hybrids with a varying genetic composition to its parent organisms.

With the evolution, hybridization has led to speciation where different subspecies were formed due to the crossing over of genetic material between individuals. The phylogeny of species was changed due to this pattern of hybridization. This was followed by the emergence of new species over time, although the time of hybridization and the speciation may not have taken place simultaneously.

What is Introgression?

Introgression is also referred to as introgressive hybridization. This process describes the gene flow between populations. Backcrossing of the hybrids formed in the F1 generation with one or both of the parents results in introgression. This results in mixing the genetic characters in a more complex manner, leading to evolution and sometimes, genetic extinction. Thus, the purpose of introgression is to incorporate an allele from one species to the gene pool of another, thus and introgression of genes takes place between the populations.

It was also observed that the alleles showing introgression can have the ability to be of vital usage and determine many speciation phenotypes. This is mainly proved through studies done with differential introgression. During differential introgression, alleles will be introgressed more and their speciation will be determined.

Introgression depends on many factors such environmental factors, the different alleles used in introgression and the behavior of the alleles, etc. Introgression is a unidirectional process, with the ability to backcross the formed F2 hybrid with one of the parents.

What are the Similarities Between Hybridization and Introgression?

• Both Hybridization and Introgression phenomena contribute to genetic extinction.
• Both Hybridization and Introgression adhere to the theories of evolution and phylogeny.
• The F1 generation is vital in both Hybridization and Introgression phenomena.

What is the Difference Between Hybridization and Introgression?

Summary – Hybridization vs Introgression

Hybridization and introgression are two main concepts that are able to make wonders in genetic, phylogenetic and evolutionary studies, as it leads to genetic extinction and new genotypes and phenotypes. Hybridization is the process of interbreeding between two genetically distinct individuals whereas introgression is the process where individuals of the same population interbreed and undergo a backcross with one or both of the parents. This is the difference between hybridization and introgression.

Reference:

1.Harrison, Richard G., and Erica L. Larson. “Hybridization, Introgression, and the Nature of Species Boundaries | Journal of Heredity | Oxford Academic.” OUP Academic, Oxford University Press, 22 Aug. 2014. Available here 

Image Courtesy:

1.’Mais ja teosint’By J LEVIN W – Own work, (CC BY-SA 4.0) via Commons Wikimedia 
2.’Inbreeding- Backcross’By Donach – Own work, (CC BY-SA 4.0) via Commons Wikimedia