Phylogenetic Tree: Construction, Importance & Types

Phylogeny is a study of evolutionary relationships. Phylogenetic Analysis is defined as a means of inferring evolutionary relationships. A phylogenetic tree is also called The "Tree of Life'' or "Dendrogram". The concept of a phylogenetic tree evolved from an ancient concept of a ladder-like evolution of life forms from moderate to powerful. The term phylogenetic or phylogenic is derived from the ancient Greek word, which refers to race, origin, or lineage. Phylogenetic trees are hypothetical means it is not a fact.

Key Terms: Phylogenetic tree, Phylogeny, outgroup, internal nodes, Terminal points, Evolutionary Tree, Fungi Phylogeny

Read More: Basic Internal Anatomy of Leaf

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What is a Phylogenetic tree?

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Phylogenetic tree is characterized as a diagrammatic portrayal of living organisms' evolutionary links. This diagrammatic representation represents how different species evolved from a species of common ancestors

The phylogenetic tree is a two-dimensional graph that depicts the evolutionary relationship between creatures that are related to each other.

Phylogenetic tree

In the above diagram, The “First true cells” are known as Ancestors. You can also see humans in the diagram, which means the human originated from the first true cells.

Molluscs and mammals are distinctly related to each other. Reptiles and Birds are closely related to each other, it is said to be a closely related organism.

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Construction of Phylogenetic Tree

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Phylogenetic tree can be constructed in two different ways-

1. Character-based method

This method is based directly on the sequence characters, therefore it is called the discrete method.The character-based method uses the aligned character for constructing the phylogenetic tree. These aligned characters include either the DNA or protein sequence during the tree inference. The two most popular character-based method is

A) Maximum parsimony

B) Maximum likelihood

2. Distance-based method

This method is based on the amount of distance or the dissimilarity between the two aligned sequences. In this method the sequence data is transformed into pairwise distances and then the matrix is used for building a tree.

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Steps To Prepare The Phylogenetic Tree

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•  Selection of an organism or a gene family
•  Selection of appropriate molecular markers
•  Amplification
•  Sequencing
•  Assembly
•  Alignment
•  Evolutionary model
•  Phylogenetic analysis
• Construction of a tree
• Evolution of a phylogenetic tree

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Types of the Phylogenetic Tree

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The four types of Phylogenetic trees are-

The four types of Phylogenetic trees

1. Rooted Tree

Make the inference about the most common ancestor of the leaves or branches of the tree (Ancestors are known in the rooted tree).

Rooted Tree

2. Un Rooted Tree

Make an illustration about the leaves or branches do not make any assumptions regarding the most common ancestors (ancestors unknown)

Un Rooted Tree

3. Bifurcating Tree

A tree that has a maximum of two descendants which come from interior nodes is known as bifurcating tree.

Bifurcating Tree

4. Multifurcating Tree

A tree that has multiple descendants which come from interior nodes is known as a multifurcating tree.

Multifurcating Tree

Example. In the below diagram you can see A, B, C, D, E points . They are known as Terminal points. Terminal points: The points which are at the terminal end are known as terminal points.

I1,I2,I3,I4 –Internal nodes/points. Internal nodes: Internal nodes are nodes from where diversion is occurring. From the diagram, we can say that D and E are closely related and B and D are distantly related.

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Importance of Phylogenetic Tree:

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Phylogenetic trees are a fundamental tool to derive useful evidence from the fields of anatomy, paleontology, embryology and molecular genetics. The following are some of the other implications of the evolutionary tree:

• Used in the search for new species.
• Used to study evolutionary histories.
• To study how the species were spread geographically.
• It is used to identify the most recent common ancestors and to recognize new closely related species that are
• To relate the milestones of the evolution of major life forms to the tree of life.
• To represent the evolutionary relationship between organisms that are believed to have some common ancestry.
• Phylogenetic trees help in tracing the infectious microbes with their evolutionary histories.

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Things to Remember

• A phylogenetic tree is a diagram that shows how organisms have changed in the period of time.
• Phylogenetic trees are only that: theories, not facts.
• Phylogenetic trees can be drawn in a variety of ways. The information carried by a tree does not change when it is rotated around its branch points.
• If two species share a recent common ancestor, they are more closely connected in trees than if they share a distant common ancestor.
• The branching pattern of a phylogenetic tree shows how species or other groups descended from a common ancestor.