Difference Between Monophyletic Paraphyletic and Polyphyletic

Key Difference – Monophyletic vs Paraphyletic vs Polyphyletic
 

A taxon is a group of organism in phylogeny. Taxa are defined for the ease of identification and classification and also to understand the relationships between the organisms. Taxa are created based on their characteristics. Some taxa include related organisms while some taxa consist of unrelated organisms. Ancestor and descendants are grouped under taxa. Monophyletic, paraphyletic and polyphyletic are such groups used in phylogenetic studies.  A monophyletic taxon is defined as a group that consists of the most recent common ancestor of a group of organisms and all of its descendants, a paraphyletic taxon is defined as a group that consists of the most recent common ancestor and some of its descendants while a polyphyletic group is defined as a group of unrelated organisms that lacks a most recent common ancestor. This is the key difference between monophyletic, paraphyletic and polyphyletic taxa.

CONTENTS

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

What is Monophyletic?

Monophyletic group is a group of organisms that includes an ancestral species and its entire descendent species. Monophyleyic group is also known as a clade. A clade is a natural kind of a group that is very important in phylogenetic classification. Monophyletic groups are created based on the shared derived characteristics. Hence, monophyletic group can visualize relationships among the organisms in a phylogenetic tree.

Figure 01: Monophyly, Paraphyly and Polyphyly

Monophyletic groups are marked or shown in cladograms. The cladogram shows the relationships and also amount of evolution by the branching order and branching length respectively. Mammalia and Aves are considered as well known monophyletic taxa.

What is Paraphyletic?

Paraphylatic group is a group of organisms that consist of an ancestral species and some of its descendant species. Not all the descendent species are included in this group. Paraphyletic group is nearly monophyletic. The paraphyletic group is created based on the symplesiomorphy. Some well known paraphyletic taxa are Pisces and Reptilia.

What is Polyphyletic?

A polyphyletic taxon is a group of organisms that lack a common ancestor. The polyphyletic group consists of unrelated organisms who are descended from more than one ancestor. It is kind of an unnatural group of organisms. Normally when a polyphyletic taxon is found, it is reclassified since it is a totally unnatural assemblage.

Figure 02: Polyphyletic group

Some well-known polyphyletic taxa are Agnatha and Insectivora.

What are the Similarities Between Monophyletic Paraphyletic and Polyphyletic?

• All these terms are used to define taxa of organisms.
• All terms are used to define a group of organisms.
• When defining, the most recent common ancestor is considered in all groups.
• All these groups explain the relatedness of the organisms.

What is the Difference Between Monophyletic Paraphyletic and Polyphyletic?

Summary – Monophyletic vs Paraphyletic vs Polyphyletic 

Organisms are classified based on their different characteristics such as morphological and molecular level characteristics. They are grouped for the purpose of identification and phylogenetic analysis. Monophyletic, paraphyletic and polyphyletic are three groups that can be identified in phylogenetic trees. The monophyletic group consists of a most recent common ancestor and its entire descendants. It is a natural group that uses in phylogeny. The paraphyletic group consists of a most recent common ancestor and some of its descendants. The polyphyletic group is an unnatural assemblage of unrelated organisms who lack a most recent common ancestor. This is the difference between monophyletic, paraphyletic and polyphyletic.

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Reference:

1.Carr, Dr Steven M. Monophyletic, Polyphyletic, & Paraphyletc Taxa. Available here 
2.Editors. “Monophyletic – Definition, Explanation and Quiz.” Biology Dictionary, 27 May 2017. Available here 
3.“Monophyly.” Wikipedia, Wikimedia Foundation, 11 Jan. 2018. Available here

Image Courtesy:

1.’Monophyly, paraphyly, polyphyly’By Original work by Petter Bøckman, revised by Peter Brown  (CC BY-SA 3.0) via Commons Wikimedia  
2.’Polyphyletic groups’By Peter Southwood – Own work, (CC BY-SA 4.0) via Commons Wikimedia 

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