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Allopatric Speciation vs. Sympatric Speciation: What's the Difference?

Edited by Aimie Carlson || By Harlon Moss || Updated on October 9, 2023
Allopatric speciation occurs when populations are separated by physical barriers; sympatric speciation occurs within a shared environment without physical barriers.

Key Differences

Allopatric speciation involves the evolution of species due to physical barriers separating populations, while sympatric speciation sees species evolve without such geographical divides.
In allopatric speciation, geographic isolation, such as mountains or rivers, may prevent populations from interbreeding, causing them to evolve differently. Conversely, sympatric speciation might arise from non-physical factors, like ecological niches or behavioral differences, within the same region.
When discussing allopatric speciation, one typically imagines islands or landmasses where certain populations become isolated and evolve separately. On the other hand, sympatric speciation might be visualized as different insect populations on the same tree but feeding on different parts, evolving into distinct species.
Allopatric speciation is often considered a more straightforward pathway to speciation due to the clear barrier preventing gene flow. In contrast, sympatric speciation is more complex, as it arises without such apparent barriers, making it a topic of much debate among scientists.
Many biologists believe allopatric speciation to be a more common mode of speciation because of its clear mechanism. However, there are documented cases of sympatric speciation, suggesting that both processes play roles in the diversification of life.

Comparison Chart


Geographic barriers
Non-geographic factors (e.g., ecological niches)


Often considered more common
Less common and more debated

Gene Flow

Prevented by physical barriers
Not prevented by physical barriers

Example Scenario

Islands or separated land masses
Different populations in the same area


Distinct populations due to isolation
Distinct populations in shared environment

Allopatric Speciation and Sympatric Speciation Definitions

Allopatric Speciation

The divergence of species due to external barriers.
The vast canyon acted as the catalyst for allopatric speciation between the animals.

Sympatric Speciation

Evolution of species within the same geographic area without physical barriers.
Different feeding habits in the same habitat led to sympatric speciation among insects.

Allopatric Speciation

Evolution of species caused by geographic isolation.
The formation of a mountain range led to allopatric speciation between populations on either side.

Sympatric Speciation

Speciation that arises from internal factors within a shared environment.
Despite living in the same lake, varying light preferences drove sympatric speciation among the fish.

Allopatric Speciation

The evolutionary process driven by geographic divisions.
After the glacier receded, allopatric speciation was evident in the northern and southern populations.

Sympatric Speciation

A speciation type that doesn't rely on physical barriers.
Sympatric speciation was evident in birds with different song patterns despite cohabitation.

Allopatric Speciation

A speciation type where geographic constraints prevent gene flow.
Allopatric speciation ensured the unique evolution of creatures on remote islands.

Sympatric Speciation

The divergence of species in the absence of external geographic divisions.
In the vast savannah, sympatric speciation occurred due to different mating calls.

Allopatric Speciation

Speciation resulting from populations separated by physical barriers.
Different islands in an archipelago can be grounds for allopatric speciation.

Sympatric Speciation

The evolutionary process occurring without geographic constraints.
The same forest saw sympatric speciation in butterflies due to different host plant preferences.


Can two species undergo sympatric speciation within a forest?

Yes, sympatric speciation can occur within a shared space like a forest due to factors like different ecological niches.

What triggers allopatric speciation?

Allopatric speciation is triggered by geographic barriers like mountains, rivers, or islands that separate populations.

What prevents gene flow in allopatric speciation?

Physical barriers like mountains or bodies of water prevent gene flow in allopatric speciation.

How does sympatric speciation differ from allopatric?

Sympatric speciation occurs without geographic barriers, often due to ecological or behavioral differences, while allopatric speciation is due to physical separation.

Is allopatric speciation more common?

Many biologists believe allopatric speciation to be more prevalent due to its clear mechanism, though both types exist.

Are there examples of sympatric speciation in plants?

Yes, plants can undergo sympatric speciation, often due to polyploidy or using different pollinators.

Can behavior lead to sympatric speciation?

Yes, behavioral differences, like varied mating calls or rituals, can drive sympatric speciation.

Can sympatric speciation occur in aquatic environments?

Yes, for example, fish in the same lake evolving differently due to varied light or depth preferences.

What's a classic example of allopatric speciation?

The Galápagos finches, which evolved on different islands, are a classic example.

How long does allopatric speciation take?

It varies, but it often requires significant time for genetic differences to accumulate.

How is gene flow maintained in sympatric speciation?

Gene flow can still occur in sympatric speciation but might be reduced due to factors like niche differentiation.

Why is sympatric speciation debated?

It's debated because it occurs without clear barriers, making it harder to prove and study compared to allopatric speciation.

Are there proven instances of sympatric speciation?

Yes, there are documented cases, though it remains a debated topic among scientists.

Can humans influence sympatric speciation?

Potentially, as changes to environments or introducing new species can create conditions for it.

Can one species undergo both speciation types?

Potentially, if different populations of a species experience varied conditions.

Which is more easily observable, allopatric or sympatric speciation?

Allopatric speciation is often more easily observed due to clear geographic divisions.

Is sympatric speciation rapid?

It can be, especially in cases driven by strong selection pressures.

Which speciation type requires a physical barrier?

Allopatric speciation requires a physical barrier.

Does every geographic barrier lead to allopatric speciation?

Not necessarily; while barriers can lead to it, other factors like time and genetic variability are crucial.

Can allopatric speciation be reversed?

If previously separated populations come together and can still interbreed, they might merge, though it's complex.
About Author
Written by
Harlon Moss
Harlon is a seasoned quality moderator and accomplished content writer for Difference Wiki. An alumnus of the prestigious University of California, he earned his degree in Computer Science. Leveraging his academic background, Harlon brings a meticulous and informed perspective to his work, ensuring content accuracy and excellence.
Edited by
Aimie Carlson
Aimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.

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