Difference Between Allopatric And Sympatric Speciation

Edited By Irshad Anwar | Updated on Jul 02, 2025 06:27 PM IST

The two major speciation modes are allopatric speciation and sympatric speciation, explaining how new species come into being. Allopatric speciation is the process by which populations of the same species become geographically isolated from one another, which blocks gene flow and allows new species to emerge. In contrast, sympatric speciation occurs without geographic separation. It is often caused by factors like ecological niche differentiation or genetic mutations within a shared environment. This is an important topic from the Evolution Chapter of Biology.

This Story also Contains

What is Speciation?
Allopatric Speciation
Sympatric Speciation
Comparison Between Allopatric and Sympatric Speciation

Difference Between Allopatric And Sympatric Speciation

What is Speciation?

Speciation is defined as the natural generative process through which new species are created from already existing species. This process is achieved by mechanisms including genetic drift and altruism and includes reproductive isolation. Genetic differentiation can be availed as the process through which a population accumulates genetic changes as a result of mutations, natural selection, and or drift.

Mating barriers that may be prezygotic or postzygotic do not allow cross-breeding between two evolving populations. Together, these mechanisms come into work to accomplish the formation of new species helping in the evolution of new and various species that exist on the face of the earth.

Allopatric Speciation

Allopatric speciation takes place in the geographical isolation of a species into distinct sub-species resulting in the formation of new species. This has the effect of keeping the isolated groups physically separated and thus does not allow gene flow from one group to the next enabling the groups to evolve in different manners.

Mechanism of Allopatric Speciation

Geographic Isolation: Rivers, mountains or seas separate the members of a population from each other causing distinct divisions.

Divergent Evolution: The groups of population get separated and are exposed to various environmental conditions and gene changes, which in due course, give rise to genetically diverse populations adapting to their surroundings. This leads to the formation of new species these populations build up a set of genetic variations as time goes on.

Examples of Allopatric Speciation

Darwin's Finches: All those finch species which are seen at present evolved from the same ancestor; however, the situation on every island is different.

Grand Canyon Squirrels: You will find two types of squirrels, the Kaibab squirrel which belongs to the north of the Grand Canyon and the Abert’s squirrel which belongs to the south of the Grand Canyon and are two different species of squirrels.

Sympatric Speciation

This is the type of speciation in which the evolution of a new species from an original ancestor species occurs physically in the same region. It is the type of speciation that happens when no geographical isolation of the population is involved.

Mechanism of Sympatric Speciation

Reproductive Isolation within the Same Geographic Area: Species in a population adapt to new conditions and develop characteristics which make them unsuitable for mating with other populations even when they are in the same geographical region.

Polyploidy, Sexual Selection, Habitat Differentiation: Mutation, such as changes in chromosome number polyploidy, may lead to reproductive isolation. Mate choice is based on sexual selection whereas choice of habitat results in differentiation of population concerning the ecological factors that cause speed of speciation.

Examples of Sympatric Speciation

Apple Maggot Flies: These flies have diverged into various subgroups depending on the type of fruit they are attracted to, while some go for apples, others for hawthorn.

Cichlid Fish in African Lakes: It is noteworthy that although all the studied fish live in the same waters – the lakes of East Africa, different cichlid species have developed different ecological and/or mating niches.

Comparison Between Allopatric and Sympatric Speciation

Feature	Allopatric Speciation	Sympatric Speciation
Geographic Isolation	Yes, populations are physically separated	No, populations are in the same geographic area
Mechanisms	Geographic barriers leading to divergence	Reproductive isolation, polyploidy, Natural selection, habitat differentiation
Examples	Darwin's finches, Grand Canyon squirrels	Apple maggot flies, cichlid fish in African lakes
Reproductive Isolation	Arises as a result of geographic separation	Occurs within a shared environment
Genetic Divergence	Driven by isolation and different selection pressures	Driven by niche differentiation and mating preferences

Also Read

Mutation Theory	Reproductive Isolation
Evidence of Evolution	Miller Urey Experiment
Mutagens	Anagenesis

Frequently Asked Questions (FAQs)

1. What is the main difference between allopatric and sympatric speciation?

The main distinction from the previous type is that it happens due to physical barriers that isolate populations and cause the development of distinct species in different environments. On the other hand, sympatric speciation occurs in one area without the separation whereby speciation might as a result of reproductive isolation, polyploidy, or ecological niches.

2. Can sympatric speciation occur in animals?

Yes, sympathy is possible for animals and thus sympatric speciation is possible. For example, cichlid fish in the African lakes demonstrate sympatric speciation wherein different species develop from the same breeding population within the same lake through differences in mating behaviour and preferences and/or the usage of benthic or limnetic zones.

3. How does geographic isolation lead to allopatric speciation?

Allopatric speciation happens through physical barriers such as mountain barriers or a river which separates a population. This leads to the inability of the isolated populations to interbreed – thus, they will undergo different paths of evolution through the mechanisms of natural selection and genetic drifts, which culminate in the formation of new species.

4. What are some examples of sympatric speciation?

Sympatric speciation can be illustrated with examples of apple maggot flies which evolve into different species depending on the type of fruits chosen and cichlid fishes of the African lakes.

5. Why is understanding speciation important in evolutionary biology?

The study of speciation is central in evolutionary biology as this field describes the process of formation, adjustment, and variety of new species. It can explain the underlying mechanisms of species to richness and assist in preservation because it demonstrates how species adapt to alterations in the environment and human interference.

6. What role does natural selection play in allopatric speciation?

Natural selection is crucial in allopatric speciation. When populations are geographically isolated, they may face different environmental pressures. Natural selection acts on these separated populations, favoring traits that are advantageous in their respective environments, leading to genetic divergence over time.

7. What are some examples of geographical barriers that can lead to allopatric speciation?

Geographical barriers that can lead to allopatric speciation include mountain ranges, rivers, oceans, deserts, or glaciers. For instance, the formation of the Isthmus of Panama separated marine populations in the Atlantic and Pacific Oceans, leading to allopatric speciation in many marine species.

8. What is the role of genetic drift in allopatric speciation?

Genetic drift plays a significant role in allopatric speciation, especially in small, isolated populations. When populations are separated, random changes in allele frequencies can occur independently in each group. Over time, this can lead to genetic divergence, even in the absence of strong selective pressures.

9. What is the "founder effect" and how does it relate to allopatric speciation?

The founder effect occurs when a small group of individuals becomes isolated from the main population, carrying only a subset of the original genetic diversity. This can lead to rapid genetic divergence in the new population. The founder effect is often associated with allopatric speciation, as it typically involves geographical isolation of a small group.

10. What is meant by "adaptive radiation" and how does it relate to allopatric speciation?

Adaptive radiation refers to the rapid diversification of a single ancestral species into many descendant species, each adapted to different ecological niches. It often occurs after allopatric speciation events, such as when a species colonizes an isolated area with diverse habitats. The Galápagos finches studied by Darwin are a classic example of adaptive radiation following allopatric speciation.

11. What is the fundamental difference between allopatric and sympatric speciation?

Allopatric speciation occurs when populations are geographically isolated, while sympatric speciation happens within the same geographical area. In allopatric speciation, a physical barrier prevents gene flow between populations, leading to divergence. In sympatric speciation, populations diverge despite occupying the same space, often due to factors like habitat specialization or sexual selection.

12. How does gene flow differ between allopatric and sympatric speciation?

In allopatric speciation, gene flow between populations is completely or significantly reduced due to physical separation. In sympatric speciation, gene flow may still occur between diverging populations, but other factors (like assortative mating or ecological specialization) counteract its homogenizing effect, allowing speciation to proceed.

13. What is the significance of reproductive isolation in both types of speciation?

Reproductive isolation is the key outcome of both allopatric and sympatric speciation. It refers to mechanisms that prevent members of different species from interbreeding or producing viable offspring. In allopatric speciation, reproductive isolation often develops as a byproduct of adaptation to different environments. In sympatric speciation, it can arise from factors like habitat specialization or changes in mating behavior.

14. How does the speed of speciation typically compare between allopatric and sympatric processes?

Allopatric speciation is generally considered to occur more rapidly than sympatric speciation. This is because geographic isolation provides a strong barrier to gene flow, allowing populations to diverge more quickly. Sympatric speciation, lacking this physical separation, often requires stronger selective pressures or unique circumstances (like polyploidy) to overcome the homogenizing effects of gene flow.

15. How does habitat specialization contribute to sympatric speciation?

Habitat specialization can lead to sympatric speciation by creating ecological niches within the same geographical area. As subpopulations adapt to different microhabitats or resources, they may develop reproductive isolation. For example, different species of palm trees in Lord Howe Island have specialized for different soil types within the same small area.

16. How can sympatric speciation occur without geographical barriers?

Sympatric speciation can occur through mechanisms like habitat specialization, sexual selection, or polyploidy. For example, individuals might specialize in different food sources within the same area, leading to reproductive isolation. Alternatively, changes in mating preferences or chromosomal mutations (like polyploidy in plants) can create barriers to reproduction within a population.

17. How does polyploidy contribute to sympatric speciation, particularly in plants?

Polyploidy, the multiplication of chromosome sets, can lead to instant sympatric speciation in plants. When an individual plant develops extra chromosome sets (often through errors in cell division), it becomes reproductively isolated from its parent population. This new polyploid individual can self-fertilize or mate with other polyploids, forming a new species within the same area as its parent species.

18. How can behavioral changes lead to sympatric speciation?

Behavioral changes, particularly in mating preferences, can contribute to sympatric speciation. If subgroups within a population develop different mating calls, courtship rituals, or timing of reproduction, it can lead to reproductive isolation. For example, some fish species have diverged sympatrically due to differences in mating colors or behaviors.

19. How do chromosomal rearrangements contribute to both allopatric and sympatric speciation?

Chromosomal rearrangements, such as inversions or translocations, can contribute to both types of speciation by creating reproductive barriers. In allopatric populations, different rearrangements may become fixed. In sympatric populations, individuals with certain rearrangements may have reduced fertility when mating with the original type, leading to reproductive isolation.

20. What is "ecological speciation" and how does it relate to both allopatric and sympatric processes?

Ecological speciation occurs when reproductive isolation evolves as a result of ecologically-based divergent selection. It can occur in both allopatric and sympatric contexts. In allopatry, populations adapt to different environments. In sympatry, subpopulations might specialize on different resources within the same area. In both cases, adaptations to different ecological niches drive the speciation process.

21. What is the "genic view" of speciation and how does it apply to both allopatric and sympatric processes?

The genic view of speciation focuses on the divergence of individual genes rather than whole genomes. It suggests that speciation can proceed even with gene flow in some parts of the genome, as long as key "speciation genes" diverge. This view is relevant to both allopatric and sympatric speciation, emphasizing that genomic divergence can be heterogeneous.

22. What is the role of hybridization in speciation, and how does it relate to allopatric and sympatric processes?

Hybridization can contribute to both allopatric and sympatric speciation. In allopatry, hybridization can occur when previously separated populations come into secondary contact. In sympatry, it can lead to new lineages through hybrid speciation. Hybridization introduces genetic variation, potentially leading to novel adaptations and reproductive isolation from parent species.

23. What is the significance of prezygotic versus postzygotic isolation mechanisms in speciation?

Prezygotic isolation mechanisms (e.g., habitat isolation, behavioral isolation) prevent mating or fertilization between species. Postzygotic mechanisms (e.g., hybrid inviability, sterility) reduce the fitness of hybrid offspring. Both can occur in allopatric and sympatric speciation, but prezygotic isolation is often more important in sympatric scenarios as it prevents wasteful hybrid mating.

24. How does island biogeography contribute to our understanding of allopatric speciation?

Island biogeography provides numerous examples of allopatric speciation. Islands offer isolated environments where populations can diverge from mainland ancestors or between islands. The Hawaiian honeycreepers and Galápagos finches are classic examples, demonstrating how geographical isolation leads to adaptive radiation and speciation.

25. What is "reinforcement" in the context of speciation, and how does it relate to allopatry and sympatry?

Reinforcement is the process where natural selection strengthens reproductive barriers between species or incipient species. It often occurs when previously allopatric populations come into secondary contact. If hybrids have reduced fitness, selection favors traits that prevent interbreeding, reinforcing species boundaries. This process bridges allopatric divergence and sympatric coexistence.

26. How does sexual selection contribute to sympatric speciation?

Sexual selection can drive sympatric speciation by causing divergence in mating preferences or sexual traits within a population. If subgroups develop different preferences for mate characteristics, it can lead to reproductive isolation. For example, cichlid fish in African lakes have diversified rapidly, partly due to sexual selection on male coloration.

27. How do ring species demonstrate aspects of both allopatric and sympatric speciation?

Ring species, such as the Ensatina salamanders in California, show a continuum between allopatric and sympatric speciation. Populations diverge around a geographical barrier, with adjacent populations able to interbreed. However, the terminal populations, which may overlap geographically, are reproductively isolated. This demonstrates how allopatric divergence can lead to sympatric species.

28. How do allochronic barriers contribute to sympatric speciation?

Allochronic barriers occur when subpopulations breed at different times (e.g., different seasons or times of day). This temporal isolation can lead to sympatric speciation by preventing gene flow between subpopulations that otherwise share the same space. For example, some coral species have diverged due to differences in spawning times.

29. What is the role of genetic architecture in facilitating or hindering sympatric speciation?

Genetic architecture, including linkage between genes affecting ecological traits and mate choice, can facilitate sympatric speciation. If genes for habitat preference are linked to genes for mating preference, it can promote rapid divergence. Conversely, if these traits are controlled by many unlinked genes, it may hinder sympatric speciation by allowing recombination to break up adaptive combinations.

30. How does the concept of "magic traits" relate to sympatric speciation?

"Magic traits" are traits that simultaneously contribute to ecological adaptation and reproductive isolation. They are particularly important in sympatric speciation as they can drive divergence despite ongoing gene flow. For example, beak size in Galápagos finches affects both feeding ability and mating calls, potentially facilitating rapid speciation.

31. How do host shifts in parasites or symbionts relate to sympatric speciation?

Host shifts can lead to sympatric speciation in parasites or symbionts. When a subpopulation adapts to a new host species, it may become reproductively isolated from the population on the original host. This can occur within the same geographical area, leading to sympatric speciation. Examples include some fruit flies that specialize on different plant hosts.

32. What is the significance of "genomic islands of divergence" in the study of speciation?

Genomic islands of divergence are regions of the genome that show high differentiation between diverging populations, while other regions remain similar. They are important in understanding both allopatric and sympatric speciation, as they represent areas resistant to gene flow. In sympatric speciation, these islands may contain genes crucial for local adaptation and reproductive isolation.

33. How does the speed of environmental change affect the likelihood of allopatric versus sympatric speciation?

Rapid environmental changes may favor sympatric speciation, as populations must adapt quickly without the luxury of geographical isolation. Conversely, gradual changes over long periods may allow for allopatric speciation as populations slowly adapt to different environments. However, rapid changes can also lead to allopatric speciation if they create sudden geographical barriers.

34. What is the role of phenotypic plasticity in speciation, and how might it differ between allopatric and sympatric contexts?

Phenotypic plasticity, the ability of an organism to change its phenotype in response to the environment, can play a role in both types of speciation. In allopatric speciation, plasticity might allow populations to persist in new environments long enough for genetic adaptation to occur. In sympatric speciation, plasticity could facilitate the initial stages of habitat specialization, potentially leading to genetic divergence.

35. How do differences in dispersal ability affect the likelihood of allopatric versus sympatric speciation?

Species with low dispersal ability are more prone to allopatric speciation, as even small geographical barriers can effectively isolate populations. Conversely, species with high dispersal ability may be more likely to undergo sympatric speciation, as they can maintain gene flow over large areas, requiring other mechanisms (like habitat specialization) for divergence to occur.

36. What is the "genomic hitchhiking" effect and how does it relate to speciation processes?

Genomic hitchhiking occurs when neutral genes near selected genes also change in frequency due to linkage. In speciation, this can lead to larger regions of the genome diverging between populations, even if only a few genes are under direct selection. This process can accelerate both allopatric and sympatric speciation by increasing overall genomic divergence.

37. How does the strength of selection pressure compare between allopatric and sympatric speciation scenarios?

Generally, sympatric speciation requires stronger selection pressures to overcome the homogenizing effects of gene flow. In allopatric speciation, weaker selection can still lead to divergence due to the absence of gene flow. However, strong selection can accelerate both processes, leading to rapid speciation in either context.

38. What is the significance of "reproductive character displacement" in speciation processes?

Reproductive character displacement occurs when traits involved in mate recognition or reproduction evolve to be more distinct in areas where related species overlap. It's often associated with reinforcement after secondary contact of allopatric populations. However, it can also play a role in sympatric speciation by enhancing reproductive isolation between diverging populations.

39. How do differences in generation time affect the rate of allopatric versus sympatric speciation?

Species with shorter generation times generally have the potential for faster speciation, whether allopatric or sympatric. This is because genetic changes can accumulate more quickly over a given time period. However, the effect may be more pronounced in allopatric speciation, where even small changes can lead to divergence. In sympatric scenarios, short generation times might allow for rapid adaptation to different niches.

40. What is the role of epigenetic changes in speciation, and how might this differ between allopatric and sympatric contexts?

Epigenetic changes, which affect gene expression without altering DNA sequence, can contribute to both types of speciation. In allopatric scenarios, different epigenetic patterns might become fixed in isolated populations. In sympatric contexts, epigenetic changes could facilitate rapid adaptation to different niches within the same area. Importantly, some epigenetic changes can be inherited, potentially accelerating divergence.

41. How does the concept of "ecological opportunity" relate to both allopatric and sympatric speciation?

Ecological opportunity refers to the availability of unoccupied ecological niches. In allopatric speciation, it often occurs when a species colonizes a new, isolated area with diverse habitats (like an island archipelago). In sympatric speciation, ecological opportunity can arise from environmental changes or the evolution of new traits that allow exploitation of previously inaccessible resources within the same area.

42. What is "hybrid speciation" and how does it challenge the traditional allopatric-sympatric dichotomy?

Hybrid speciation occurs when a new species forms from the hybridization of two distinct parent species. It challenges the allopatric-sympatric dichotomy because it can occur in both contexts. In sympatry, it can lead to instant reproductive isolation due to chromosomal differences. In allopatry, hybrids might colonize new habitats. Hybrid speciation blurs the lines between these traditional categories.

43. How do differences in mating systems (e.g., selfing vs. outcrossing plants) affect the likelihood of allopatric versus sympatric speciation?

Mating systems can significantly influence speciation processes. Selfing plants may be more prone to rapid speciation, especially in allopatric scenarios, as they can quickly fix new mutations. Outcrossing plants might be more likely to undergo sympatric speciation through mechanisms like polyploidy. However, outcrossing can also facilitate adaptation in allopatry by maintaining genetic variation.

44. What is the significance of "genomic conflict" in speciation, and how might it differ in allopatric versus sympatric contexts?

Genomic conflict, such as meiotic drive or cytonuclear incompatibilities, can contribute to reproductive isolation. In allopatric populations, different conflicts might evolve independently. In sympatric scenarios, genomic conflict could drive rapid divergence despite gene flow. For example, selfish genetic elements might spread in one population but be suppressed in another, leading to incompatibilities.