Allopatric Speciation Definition
Allopatric speciation is speciation that happens when two populations of the same species become isolated from each other due to geographic changes. Speciation is a gradual process by which populations evolve into different species. A species is itself defined as a population that can interbreed, so during speciation, members of a population form two or more distinct populations that can no longer breed with each other.
Steps of Allopatric Speciation
- A geographic change separates members of a population into more than one group. Such changes could include the formation of a new mountain range or new waterway, or the development of new canyons, for example. Also, human activities such as civil engineering, agriculture, and pollution can have an effect on habitable environments and cause some members of a population to migrate.
- Different gene mutations occur and build up in the different populations over time. The different variations of genes may lead to different characteristics between the two populations.
- The populations become so different that members of the different populations can no longer breed with each other anymore if were they to be in the same habitat in the same time. If this is the case, allopatric speciation has occurred.
The following diagram represents an experiment on fruit flies where the population was forcibly separated and the two groups were fed a different diet. After many generations the flies looked different and preferred to mate with flies from their own group. If these two populations continued to diverge for a long time, they could become two different species through allopatric speciation.
Examples of Allopatric Speciation
Darwin’s Finches
A major example of allopatric speciation occurred in the Galapagos finches that Charles Darwin studied. There are about 15 different species of finches on the Galapagos islands, and they each look different and have specialized beaks for eating different types of foods, such as insects, seeds, and flowers. All of these finches came from a common ancestor species that must have emigrated to the different islands. Once populations were established on the islands, they became isolated from each other and different mutations arose. The mutations that caused the birds to be most successful in their respective environments became more and more prevalent, and many different species formed over time. When many new species emerge from one common ancestor in a relatively quickly geological timeframe, this is called adaptive radiation.
Grand Canyon Squirrels
When the Grand Canyon was formed, it created a natural barrier between the squirrels living in the area. About 10,000 years ago, the squirrel population was separated from each other by this geographic change and could no longer live in the same area. Over thousands of years, the divided squirrel populations became two different species. Kaibab squirrels live on the north rim of the canyon and have a small range, while Abert squirrels live on the south rim and live in a much larger range. Members of these two species have a similar size, shape, and diet, and slight color differences, but they are no longer in contact with each other and have become so different during their separation that they are now separate species.
The Four Types of Speciation
There are three other types of speciation besides allopatric speciation: peripatric, parapatric, and sympatric. Peripatric and parapatric speciation are similar to allopatric speciation because in these types, populations also get isolated and this causes speciation. Sympatric speciation, on the other hand, occurs when the members of different populations live in the same area but speciation still occurs.
Peripatric Speciation
Peripatric speciation occurs when members on the periphery, or border, of a large population separate off from the main group and become a new species over time. It can be difficult to distinguish from allopatric speciation. Peripatric speciation occurs when the population that breaks off enters a different biological niche, such as eating a different food or living in a different environment. Also, these new populations that break away from the main one are usually small, so this can have an effect on the proportion of certain characteristics in the new population compared with the old one. For example, say there is a population of birds that are mostly blue, but some are red. A smaller group of birds breaks off from the main group, and most of this smaller group are red. Their offspring will probably also be mostly red, which is different than the main group. This type of change in the frequency of genes is called genetic drift. Over time, many changes may occur, and these combined with the effects of genetic drift can cause new species to arise.
Parapatric Speciation
Parapatric speciation occurs when subpopulations of the same species are mostly isolated from each other, but have a narrow area where their ranges overlap. This may be due to a partial geographic barrier or an unequal distribution of members of the subpopulations. It can occur between multiple subpopulations next to each other where all the populations next to each other can interbreed, but each subpopulation is so slightly different that the members on the extreme ends would not be able to interbreed with each other. This is known as a ring species.
Sympatric Speciation
Sympatric speciation is very different from the other forms because new species emerge from populations living in highly overlapping or even identical areas. It may be more common in bacteria than in multicellular organisms because bacteria can transfer genes to each other as well as transfer genes to offspring when they divide. It is not known how often sympatric speciation occurs, and it is much rarer than the other types of speciation, but there have been some examples seen in nature. One such example is seen in cichlid fish in Tanzania that live in a small volcanic crater lake. The population has two very different ectomorphs, or forms: a yellow-green one that lives by the shore, and a blue-black one that lives by the bottom of the lake. By looking at the fishes’ DNA, researchers could see that the two ectomorphs were very different genetically. It is believed that these two forms are currently in the gradual process of speciation.
- Speciation – The process by which new species are formed.
- Adaptive Radiation – When many new species evolve from an ancestral species in a relatively short evolutionary timeframe.
- Mutation – A change in the genetic code that may lead to different characteristics in an individual.
- Ectomorph – A distinct form of an organism in a population; this word is also used to refer to a person with a naturally lean, slender body type.
Quiz
1. Which phrase describes allopatric speciation?
A. A group of members on the border of a population split off and become a separate species
B. Two populations become geographically isolated and become separate species
C. Two populations become separate species without becoming geographically isolated
D. Subpopulations are mostly isolated from each other but overlap in a small area of their range
Answer to Question #1
B is correct. During allopatric speciation, two populations become separate species when separated by a geographic barrier.
2. Which situation is NOT an example of allopatric speciation?
A. Darwin’s finches evolved differently on different islands from a single common species
B. Squirrel populations were separated via the Grand Canyon and became separate species
C. A primate population was divided by the Congo River and one group evolved into bonobos while the other evolved into chimpanzees
D. A group of birds on the edge of a population’s range entered a different niche and eventually evolved into a different species
Answer to Question #2
D is correct. Choice D does not describe allopatric speciation; it describes peripatric speciation, which is when members of a population on the border of the range break off and evolve into a different species.
3. Which type of speciation can occur even when two populations occupy the same range?
A. Sympatric speciation
B. Allopatric speciation
C. Peripatric speciation
D. Parapatric speciation
Answer to Question #3
A is correct. Sympatric speciation is when a new species develops from two groups of the same species that occupy the same range. It can be seen occurring in the different ectomorphs of the cichlid fish that live in the same lake in Tanzania.
FAQs
Allopatric Speciation: Definition & Examples | Biology Dictionary? ›
Allopatric speciation is a type of speciation in which biological populations are physically isolated by an extrinsic barrier and evolve intrinsic (genetic) reproductive isolation, such that if the barrier breaks down, individuals of the population can no longer interbreed. Example: Charles Darwin's Galápagos Finches.
What is a good example of allopatric speciation? ›When Arizona's Grand Canyon formed, squirrels and other small mammals that had once been part of a single population could no longer contact and reproduce with each other across this new geographic barrier. They could no longer interbreed. The squirrel population underwent allopatric speciation.
What does allopatric mean easy definition? ›Allopatry, meaning 'in another place', describes a population or species that is physically isolated from other similar groups by an extrinsic barrier to dispersal. From a biogeographic perspective, allopatric species or populations are those that do not have overlapping geographic ranges (Figure 1a).
What are examples of allopatric and sympatric speciation? ›| Allopatric Speciation | Sympatric Speciation |
|---|---|
| Emerging new species speed | |
| Slow | Fast |
| Example | |
| Squirrels in the Grand Canyon, Darwin's Finches, etc. | Examples include wheat, cultivated corn, tobacco, etc. |
Allopatric speciation - the formation of a new species in populations that are geographically isolated from one another. Due to geographic isolation. - Example: A mountain range may emerge and gradually split a population. Or a large lake may subside and form smaller lakes, with their populations now isolated.
What is an example of allochronic speciation? ›Yearly allochrony includes perhaps the most famous example of true allochronic speciation: several species of periodical cicadas (Magicicada spp.) with two life cycles, emerging after 13 or 17 years, occur in North America (Marshall & Cooley, 2000).
Are polar bears an example of allopatric speciation? ›The black bear and polar bear are an example of allopatric speciation, as they evolved from a common ancestor that was separated into two populations by the formation of the Bering Land Bridge, which connected North America and Asia during the last ice age.
What is allopatric speciation AP Biology? ›In allopatric speciation, organisms of an ancestral species evolve into two or more descendant species after a period of physical separation caused by a geographic barrier, such as a mountain range, rockslide, or river.
What is the definition of allopatric speciation quizlet? ›Allopatric speciation. The formation of a new species as a result of an ancestral population's becoming isolated by a geographic barrier.
Which of the following best describes allopatric species? ›Answer and Explanation: Allopatric speciation results from the separation of members of a population by a physical obstruction.
What are two examples of sympatric speciation? ›
In real life, there are two well-known examples of sympatric speciation. First is the development of blue-colored cichlid fish versus red-colored cichlid fish in an African cichlid. Second is the current emergence of the apple maggot fly while living among their ancestral species, the hawthorn maggot fly.
Is allopatric speciation an example of evolution? ›The biological equivalent is "allopatric speciation," an evolutionary process in which one species divides into two because the original homogenous population has become separated and both groups diverge from each other.
What causes allopatric speciation? ›Allopatric speciation is a mechanism to evolve reproductive isolation; it is caused by the accumulation of genetic differences between populations while they are geographically isolated.
Are humans allopatric speciation? ›Humans can undergo allopatric speciation. Allopatric speciation is the process in which physical separation allows a reproductive barrier to develop between related organisms.
What is sympatric speciation in biology? ›Sympatric speciation, from the Greek 'same place', involves the splitting of an ancestral species into two or more reproductively isolated groups without geographical isolation of those groups.
What is allopatric other country speciation? ›Allopatric Speciation: the Role of Isolation in Speciation
Only then can natural selection or perhaps genetic drift produce distinctive gene pools. It is no accident that the various races (or "subspecies") of animals almost never occupy the same territory. Their distribution is allopatric ("other country").
Midas cichlids inhabiting small and remote crater lakes in Nicaragua are traditionally considered to be one of the best examples of sympatric speciation and lend themselves to test the different evolutionary scenarios that could lead to apparent sympatric speciation since the system is relatively small and the source ...
What is an example of sympatric speciation in birds? ›Song learning and sexual imprinting explain the recent diversification of brood parasitic indigobirds (genus Vidua), the best and perhaps only example of sympatric speciation in birds (Fig. 2).
What would be an example of sympatric speciation quizlet? ›Some animals and plants appear to have diverged while living side by side—a process called sympatric speciation. One of the best examples of sympatric speciation can be found in Lake Apoyo, which formed a crater of an extinct volcano in Nicaragua.
Is allopatric speciation more common in animals? ›Recent attempts to quantify the importance of allopatric versus sympatric speciation using comparative methods called "age-range correlation" (ARC) suggest that allopatric speciation is more common than sympatric speciation.
Is allopatric speciation divergent? ›
Divergent evolution is typically exhibited when two populations become separated by a geographic barrier (such as in allopatric or peripatric speciation) and experience different selective pressures that drive adaptations to their new environment.
What type of speciation is a polar bear? ›Based on morphology and a phylogenetic analysis of their nuclear genomes, polar bears and brown bears are monophyletic sister species (Fig.
What is allopatric vs sympatric vs Parapatric speciation? ›Allopatric populations are geographically separated from each other, while parapatric or sympatric populations coexist in the same habitat. Parapatric populations occupy distinct niches in their environment and are thus separated by ecological factors, while sympatric species share the same ecological niche.
What is the allopatric speciation model answer? ›Allopatric speciation is the formation of two species from an original one due to geographical isolation. Sympatric speciation is the formation of two species from one original species due to reproductive isolation whilst occupying the same geographical location.
What is allopatric speciation Britannica? ›…that are completely separated (allopatry) by a physical barrier, such as a mountain range, river, or desert. The separated populations adapt to their own unique environments, becoming so genetically different from one another that members of one population cannot breed with members of the other.
Which statement is true of allopatric speciation? ›The correct answer is c; a geographic separation occurs between the subpopulations. The allopatric speciation occurs due to geographical barriers such as water bodies and mountain range.
Which of the following is the first step in allopatric speciation? ›Geographic isolation is the first step in allopatric speciation.
Which of the scenarios would most likely lead to allopatric speciation? ›Answer A - the formation of a new lake - is a sufficient barrier to cause allopatric speciation.
What type of speciation is most common in animals? ›Allopatric speciation, the most common form of speciation, occurs when populations of a species become geographically isolated. When populations become separated, gene flow between them ceases.
Where is allopatric speciation common? ›A major example of allopatric speciation occurred in the Galapagos finches that Charles Darwin studied. There are about 15 different species of finches on the Galapagos islands, and they each look different and have specialized beaks for eating different types of foods, such as insects, seeds, and flowers.
Is allopatric speciation rare? ›
While allopatry is a widely accepted mode of speciation and parapatry may not be uncommon, but difficult to prove (Coyne and Orr, 2004), sympatric speciation between populations that overlap extensively in their geographic distributions is more controversial.
Are ring species allopatric? ›A ring species is an alternative model to allopatric speciation, "illustrating how new species can arise through 'circular overlap', without interruption of gene flow through intervening populations…" However, Jerry Coyne and H. Allen Orr point out that rings species more closely model parapatric speciation.
Is allopatric speciation genetic drift? ›Allopatric speciation results from geographic isolation between populations. In the absence of gene flow, reproductive isolation arises gradually and incidentally as a result of mutation, genetic drift and the indirect effects of natural selection driving local adaptation.
What happens if allopatric speciation occurs after a population? ›Allopatric speciation has occurred after a population splits into two distinct populations. Which would be the MOST likely result if the two species were reunited after many generations? The two populations would not be able to interbreed. The two populations would be able to breed, producing fertile offspring.
What is a real life example of sympatric speciation? ›For example, the insect, Rhagoletis pomonella (apple maggot fly), is an example of sympatric speciation. Initially, the apple maggot flies lay their eggs on hawthorn fruit (a relative of apple). In the 19th century, a distinct form of maggot fly emerged that lay eggs on apples only.
What is a real life example of speciation? ›Galapagos Finches
A real-life example of speciation is the diversity of finches that live on a chain of islands called the Galapagos Islands. On the Galapagos Islands, there are 13 species of finch that can be traced to a single founding ancestor.
Habitat isolation can occur at different spatial scales that range from “macrospatial” (a form of allopatric speciation, where gene flow between populations is absent due geographic separation) to “microspatial” (where distinct populations co-occur geographically but rarely interbreed because of adaptations to ...
Why is allopatric speciation important in geographic isolation? ›Islands epitomize allopatric speciation, where geographic isolation causes individuals of an original species to accumulate sufficient genetic differences to prevent them breeding with each other when they are reunited.
Which of the following is an example of sympatric speciation *? ›For example, the insect, Rhagoletis pomonella (apple maggot fly), is an example of sympatric speciation. Initially, the apple maggot flies lay their eggs on hawthorn fruit (a relative of apple). In the 19th century, a distinct form of maggot fly emerged that lay eggs on apples only.
Which situation would most likely lead to allopatric speciation? ›Due to a geographical barrier, allopatric speciation occurs, resulting in the development of new and unique species from existing ones. Geographic barriers, such as a river or a valley, that have recently formed, causing species separation and allopatric speciation.
What is allopatric speciation AP biology? ›
In allopatric speciation, organisms of an ancestral species evolve into two or more descendant species after a period of physical separation caused by a geographic barrier, such as a mountain range, rockslide, or river.
Why are Darwin's finches an example of allopatric speciation? ›Darwin's finches are a group of birds that diversified on the Galapagos islands after arriving from South America. They each evolved on different islands which are separated from each other by large amounts of water. They are thus an example of allopatric speciation.
What is the most common sympatric speciation? ›One classic example of sympatric speciation is the emergence of the North American apple maggot fly. This insect is also known as the hawthorn maggot fly and both share the same taxonomic name. The hawthorn maggot fly is the ancestral species, which only feeds on and lays eggs upon hawthorn fruit.
What are some examples of sympatric speciation in mammals? ›A rare example of sympatric speciation in animals is the divergence of "resident" and "transient" orca forms in the northeast Pacific. Resident and transient orcas inhabit the same waters, but avoid each other and do not interbreed.
What is the most common form of sympatric speciation? ›Sympatric speciation occurs when populations of a species that share the same habitat become reproductively isolated from each other. This speciation phenomenon most commonly occurs through polyploidy, in which an offspring or group of offspring will be produced with twice the normal number of chromosomes.
What increases allopatric speciation? ›The allopatric speciation process is aided by geographic separation of species. In speciation, the distance between separated populations is critical, and the greater the distance between species, the faster the process of allopatric speciation occurs.
What are the two stages allopatric speciation typically occurs? ›Biologists group allopatric processes into two categories: dispersal and vicariance. Dispersal is when a few members of a species move to a new geographical area, and vicariance is when a natural situation arises to physically divide organisms.