Difference Between Geographic and Reproductive Isolation

The key difference between geographic and reproductive isolation is that the geographic isolation is a category of reproductive isolation that refers to the separation of populations of organisms from mating or exchanging their genetic material by physical boundaries while reproductive isolation refers to a set of mechanisms that prevent species from mating and producing fertile offspring.

Fertilization is the union of a sperm and an egg to form a diploid zygote during the sexual reproduction. If the produced zygote is mature, it will eventually grow into a healthy fertile offspring. therefore, reproductive isolation is a process that prevents the formation of a fertile offspring. This prevention can occur during the fertilization process or after fertilization. Anyhow, in the end, it creates a barrier to produce a fertile offspring which can give birth to another fertile offspring. Among the different mechanisms, geographic isolation is a factor of reproductive isolation.

CONTENTS

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

What is Geographic Isolation?

Geographic isolation refers to the separation of closely related species from mating and producing fertile offspring by physical barriers such as rivers, mountains, etc. It is a type of reproductive isolation. The species cannot get together due to the fact that they are living in different environments or in different geographic areas.

When they live in different environments, they acquire different characteristics and undergo natural selection. Eventually, they become different. This can lead to speciation. In the end, they evolve as a different species, and they lose the ability to reproduce successfully with each other. As an example, two population live in two islands cannot mate with each other due to this geographical isolation. Hence, they tend to reproduce with the members who live on the same island. This geographic isolation can occur as an accident or coincidence. Isolation by barriers, isolation by distance, isolation after an event and isolation by separation are several factors that can cause geographic isolation.

What is Reproductive Isolation?

Reproductive isolation is an evolutionary mechanism which leads to speciation or the formation of new and distinct species. It is a set of mechanism which prevents the closely related species from reproduction and producing fertile offspring. Thus, their mating possibilities will be blocked by several factors.

Thus, prezygotic isolation and postzygotic isolation are the two main categories of reproductive isolation. Prezygotic isolation prevents fertilization, and postzygotic isolation prevents the formation of the fertile offspring after fertilization. Geographical isolation is one type of prezygotic isolation. Postzygotic isolation explains the inability of the produced zygote to become into a fertile offspring. Reproductive isolation is critical for speciation. Speciation is the formation of new species in the course of evolution. Due to reproductive isolation and physiological and behavioural patterns, speciation occurs.

What are the Similarities Between Geographic and Reproductive Isolation?

• Geographical isolation is a type of reproductive isolation.
• Both are responsible for speciation.
• Geographic and Reproductive Isolation prevent the formation of fertile offspring.

What is the Difference Between Geographic and Reproductive Isolation?

The geographic isolation is one of the types of reproductive isolation. Therfore, there is not much difference between geographic isolation and  reproductive isolation other than the specific categorization due to the mechanism of isolation. Geographic isolation separates individuals of the closely related species from mating by geographical barriers such as mountains, water bodies, etc. Reproductive isolation is a collection of mechanisms, which is critical for speciation in order to prevent different species from producing fertile offspring.

Summary – Geographic vs Reproductive Isolation

Reproductive isolation is mainly in two forms; prezygotic isolation and postzygotic isolation. Prezygotic isolation prevents fertilization. Geographic isolation is a type of prezygotic isolation in which physical barriers prevent the meeting of individuals and mating with each other. This is the difference between geographic isolation and reproductive isolation.

Reference:

1.“Reproductive Isolation.” Egyptian Journal of Medical Human Genetics, Elsevier. Available here  
2.“Reproductive Isolation.” Wikipedia, Wikimedia Foundation, 18 Aug. 2018. Available here  

Image Courtesy:

1.”Reproductive Isolation on California Salamander population”By Gary Nafis, Alan Barron, and Thadius856, (CC BY-SA 4.0) via Commons Wikimedia 
2.”Speciation modes”By Ilmari Karonen – Adapted from: Spring 2006, Lecture Notes for EVOLUTION AND BIODIVERSITY class (BIL 160 Section HJ) by Dr. Dana Krempels, dana at miami dot edu., (CC BY-SA 3.0) via Commons Wikimedia