What is the Difference Between Anagenesis and Cladogenesis

The key difference between anagenesis and cladogenesis is that anagenesis is a process that undergoes phyletic evolution within a single species of organisms, while cladogenesis is a type of branching evolution where the ancestral species splits into several new species.

Evolution is a process that involves changes in the heritable characteristics of biological populations that occurs over successive generations. In other words, it is the process of biological change along with time. Evolution happens through different mechanisms. Anagenesis and cladogenesis are two types of such mechanisms. During anagenesis, a single gene pool transforms into another gene pool, while during cladogenesis, a single gene pool is split into different gene pools.

CONTENTS

1. Overview and Key Difference
2. What is Anagenesis 
3. What is Cladogenesis
4. Similarities – Anagenesis and Cladogenesis
5. Anagenesis vs Cladogenesis in Tabular Form
6. Summary – Anagenesis vs Cladogenesis

What is Anagenesis?

Anagenesis is a process by which evolutionary change occurs in a single lineage of organisms where one taxon is replaced by another taxon without branching. In other words, it is a progressive evolution or phyletic evolution. This occurs when individuals or a particular species specializes in responding to an external environmental stimulus. This promotes the species to a higher level through continuous increment in complexity and the perfection of the adaptations. During anagenesis, a single gene pool converts to another gene pool.

Characteristics of anagenesis include the division of labor in body parts, increased complexity of the central nervous system and related organs, increased complexity of organs to improve the function and rationalization, and increased resistance to the changes in the external environmental stimuli. There are three main types of anagenesis based on the speed of the process. They are tachytely, horotely, and bradytely. Tachytely is a rapid type of anagenesis where the replacement of taxon occurs within a short period. Bradytely is a slow type of anagenesis, while horotely anagenesis proceeds at a moderate speed.

What is Cladogenesis?

Cladogenesis is a process by which evolutionary change of a species occurs where the new species are branched off from a common ancestral species. This is the common type of mode of speciation with response to external environmental stimuli. During cladogenesis, more than one species is developed from a single species. Hence, during cladogenesis, a single gene pool converts into different gene pools. This process brings biological diversity to the environment, and it is an active evolutionary process. Branching evolution is another term to describe the cladogenesis process.

With reference to speed, we can classify cladogenesis into three types. They are tachyschizia, horoschizia, and bradyschizia. During tachyschizia, lineages split rapidly due to the extinction of competitors or invasion of new habitats. In such instances, rapid diversification occurs to adapt to the new environment with favorable opportunities by increasing their number. During horoschizia and bradyschizia, cladogenesis occurs at a moderate rate and slow rate, respectively.

What are the Similarities Between Anagenesis and Cladogenesis?

• Anagenesis and cladogenesis are types of evolutionary mechanisms.
• Both occur in response to external environmental stimuli.
• Moreover, these mechanisms lead to speciation.
• They are categorized into subtypes by the speed of occurrence.

What is the Difference Between Anagenesis and Cladogenesis?

The key difference between anagenesis and cladogenesis is that anagenesis is a process that undergoes phyletic evolution within a single species of organisms, while cladogenesis is a type of branching evolution that splits the ancestral species into several new species. During anagenesis, a single gene pool converts into another gene pool, but during cladogenesis, a single gene pool splits into different gene pools. Moreover, based on the speed of the process, there are three types of anagenesis and cladogenesis. Anagenesis types are tachytely, horotely, and bradytely. Cladogenesis types are tachyschizia, horoschizia, and bradyschizia.

The below infographic presents the differences between anagenesis and cladogenesis in tabular form for side by side comparison.

Summary – Anagenesis vs Cladogenesis

Evolution is a process in which change in the heritable characteristics of biological populations occurs over successive generations. Anagenesis and cladogenesis are two types of such mechanisms. The key difference between anagenesis and cladogenesis is that anagenesis is a process that undergoes phyletic evolution within a single species of organism. Cladogenesis is a type of branching evolution that splits the ancestral species into several new species. In anagenesis, a single gene pool transforms into another gene pool. However, in cladogenesis, a single gene pool splits into different gene pools.

Reference:

1. “Cladogenesis.” An Overview | ScienceDirect Topics.
2. “Anagenesis.” Encyclopædia Britannica, Encyclopædia Britannica, Inc.

Image Courtesy:

1. “Centrosaurine anagenesis” By FunkMonk, based on figures in:[2] and File:Yehuecauhceratops-1.png – Own work, based on figures in:[1] and File:Yehuecauhceratops-1.png (CC BY 4.0) via Commons Wikimedia
2. “Speciation cladogram subtypes” By Faustino Núñez Hernández – Own work (CC BY-SA 3.0) via Commons Wikimedia