Speciation and Reproductive Isolation

Speciation is the process by which new species arise. It occurs when populations of a single species become reproductively isolated from each other and diverge genetically to the point where they can no longer interbreed to produce fertile offspring. Understanding the mechanisms of speciation is essential for explaining the diversity of life on Earth.

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What Is Speciation?

Speciation is the formation of a new species. Recall that a species is defined (using the biological species concept) as a group of organisms that can interbreed to produce fertile offspring and are reproductively isolated from other groups.

For a new species to form, a population must be split into two or more groups that are reproductively isolated — they can no longer exchange genes. Once isolated, the groups accumulate different genetic changes over time (through natural selection and genetic drift) until they become so genetically different that they can no longer interbreed, even if they come back into contact.

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Allopatric Speciation

Definition

Allopatric speciation occurs when populations are separated by a geographical barrier — a physical obstacle that prevents gene flow between the populations.

Process — Step by Step