Summary
Speciation after a geographic barrier separates populations, as with Darwin's finches on separate islands.
In depth
A river, mountain, ocean or glacier splits a population (vicariance) or a few individuals colonise a new area (dispersal). Isolated populations undergo different selection and drift until they cannot interbreed.
It is considered the most common mode.
The most widely accepted mode, since geographic isolation removes gene flow and lets drift and selection act independently. Examples include the snapping shrimp on the two sides of the Isthmus of Panama (closing about 3 million years ago) and the Galapagos finches isolated on islands. Peripatric speciation is a variant in which a small founder population diverges rapidly.
Evidence includes more closely related species being found in adjacent but separated areas, and the sister species of many on either side of a barrier. Eventually, if populations come into contact, isolating mechanisms decide whether they merge, coexist or hybridise.
Example: Abert's and Kaibab squirrels were separated by the Grand Canyon, and are now distinct forms.
Frequently asked questions
What is Allopatric Speciation?
Speciation after a geographic barrier separates populations, as with Darwin's finches on separate islands.
Which area of biology covers Allopatric Speciation, and how advanced is it?
Allopatric Speciation is one of the 53 topics in Evolution. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Speciation, Adaptive Radiation, Divergent Evolution.
Can you give an example of Allopatric Speciation?
Isthmus of Panama formation separated snapping shrimp populations on the Pacific and Caribbean sides, which became distinct species.
What should I learn before Allopatric Speciation?
Work through the Beginner topics in Evolution first, such as Evolution, Natural Selection, Charles Darwin, then return to Allopatric Speciation. Intermediate topics assume the Beginner vocabulary.
What topics are related to Allopatric Speciation?
The closest topics to Allopatric Speciation are Speciation, Adaptive Radiation, Divergent Evolution, Founder Effect and Bottleneck. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Allopatric Speciation?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Allopatric Speciation. To practise the whole of Evolution, use the Evolution quiz.
How is Allopatric Speciation different from Speciation?
Allopatric Speciation: Speciation after a geographic barrier separates populations, as with Darwin's finches on separate islands. Speciation: The formation of new species when populations diverge enough to become reproductively isolated. Read both side by side and note what each one explains.
How should I study Allopatric Speciation step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Speciation and explain the difference aloud. Finally, take the Evolution quiz and come back to this page for any question you miss.