Speciation

Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Ornithologist Ernst Mayr formulated the standard definition of species as groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups.

Mechanisms

Speciation depends on two separate phenomena: genetic divergence and reproductive isolation. Genetic divergence is the process where a group of organisms share a common ancestor, but due to mutations, selection and genetic drift, they accumulate independent genetic differences. Reproductive isolation involves barriers to gene flow, which can either be pre-zygotic or post-zygotic.

Genetic Divergence

Genetic divergence is the process where a group of organisms share a common ancestor, but due to mutations, selection and genetic drift, they accumulate independent genetic differences. This can lead to the formation of new species.

Reproductive Isolation

Reproductive isolation involves barriers to gene flow, which can either be pre-zygotic or post-zygotic. Pre-zygotic barriers prevent fertilization from occurring. Post-zygotic barriers prevent the formation of fertile offspring.

Types of Speciation

There are four modes of natural speciation, based on the extent to which speciating populations are isolated from one another: allopatric, peripatric, parapatric, and sympatric. Speciation may also be induced artificially, through animal husbandry, cultivation, or laboratory experiments.

Allopatric Speciation

Allopatric speciation is speciation that occurs when biological populations of the same species become vicariant, or isolated from each other to an extent that prevents or interferes with genetic interchange.

Peripatric Speciation

Peripatric speciation is a mode of speciation in which a new species is formed from an isolated peripheral population.

Parapatric Speciation

Parapatric speciation is a mode of speciation in which species are formed across large geographic distances.

Sympatric Speciation

Sympatric speciation is the process through which new species evolve from a single ancestral species while inhabiting the same geographic region.

See Also

• Evolution
• Genetic drift
• Mutation
• Natural selection

References

Speciation Resources
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