Allopatric speciation (from Ancient Greek ἄλλος (állos) 'other', and πατρίς (patrís) 'fatherland') – also referred to as geographic speciation, vicariant speciation, or its earlier name the dumbbell model – is a mode of speciation that occurs when biological populations become geographically isolated from each other to ...

Is there gene flow in allopatric speciation?

A geographically-continuous population has a gene pool that is relatively homogeneous. Gene flow, the movement of alleles across the range of the species, is relatively free because individuals can move and then mate with individuals in their new location. This is known as allopatric speciation. ...

How is gene flow affected by allopatric speciation?

In allopatric speciation, postzygotic genetic incompatibilities accumulate while populations are geographically isolated. These cause reproductive isolation when populations come back into contact.

What is the result of allopatric speciation?

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. Sometimes barriers, such as a lava flow, split populations by changing the landscape.

Does speciation cause gene flow?

More specifically, ecological speciation is defined as the process by which barriers to gene flow evolve between populations as a result of ecologically-based divergent selection between environments. This process makes some simple predictions.

Speciation

28 related questions found

Why does allopatric speciation occur?

Allopatric speciation occurs when a new species evolves in geographic isolation from its ancestor. It can happen like this: One species could split into two if a physical barrier, such as a new river, divided its geographic range. ... There would now be two species where there was formerly one.

Why does speciation require an interruption of gene flow?

It is widely accepted that speciation requires an interruption of gene flow between populations: ongoing gene exchange is considered a major hindrance to population divergence and, ultimately, to the evolution of new species.

What is allopatric speciation by dispersal?

Allopatric speciation events can occur either by dispersal, when a few members of a species move to a new geographical area, or by vicariance, when a natural situation, such as the formation of a river or valley, physically divide organisms.

What are the important differences between the Vicariant and founder event modes of allopatric speciation?

In Vicariant speciation, climatic or geological changes occur which fragment the habitat of a species. This fragmentation produces impenetrable barriers. In founder event type of speciation, a small number of a species are dispersed to an unknown area where no other members of their species are present.

What is the main difference between dispersal and vicariance?

The key difference between dispersal and vicariance is that dispersal is the migration of a part of the population into new areas across a preexisting geographic barrier while vicariance is the division of the population due to the appearance of a new geographical barrier.

How does migration affect gene flow?

Migrants change the distribution of genetic diversity among populations, by modifying allele frequencies (the proportion of members carrying a particular variant of a gene). High rates of gene flow can reduce the genetic differentiation between the two groups, increasing homogeneity.

What affects gene flow?

In humans gene flow usually comes about through the actual migration of human populations, either voluntary or forced. Although gene flow does not change allele frequencies for a species as a whole, it can alter allele frequencies in local populations.

How does gene flow prevent speciation?

Gene flow strongly acts against speciation, by recombining the gene pools of the groups, and thus, repairing the developing differences in genetic variation that would have led to full speciation and creation of daughter species.

Can divergence of allopatric populations lead to reproductive isolation?

In allopatric species, a genetic basis for reproductive isolation is not directly required because populations already are physically isolated. Reproductive barriers therefore evolve as a by-product of genetic divergence rather than as reinforcement of reproductive isolation.

What does allopatric speciation require?

There are several factors required for allopatric speciation to occur like isolation, time and natural selection. Earthquakes, floods and migration are ways a group of individuals of the same species can become isolated.

Why allopatric speciation is more common?

Allopatric speciation, the most common form of speciation, occurs when populations of a species become geographically isolated. ... Over time, the populations may become genetically different in response to the natural selection imposed by their different environments.

What is the difference between founder effect and allopatric speciation?

Strong genetic drift in the founder population could lead to an immediate evolutionary divergence from the ancestral population. ... Founder effect speciation is a special case of allopatric speciation in which one of the geographical isolates was established from a small number of individuals.

Why the Darwins Finches on Galapagos Islands underwent allopatric speciation?

Allopatric speciation

Darwin's finches on the Galapagos Islands, which may have speciated allopatrically because of volcanic eruptions that divided populations, is a famous example. Fourteen species of Galapagos finches that evolved from a common ancestor.

What is the name of the flow which becomes limited when populations are geographically isolated?

Speciation : Example Question #9

Allopatric speciation occurs when one population separates into two geographically isolated populations. The geographic isolation prevents gene transfer and reproduction, allowing for genetic divergence between the two populations.

What is the mechanism of allopatric speciation?

Introduction. Allopatric speciation (i.e. the formation of species caused by geographical splitting of a genetic pool), can arise by one of two mechanisms: vicariance or long-distance dispersal. Vicariance takes place when a geographic barrier arises, disrupting the gene flow between subpopulations.

What is Allopatric mechanism?

Allopatric speciation (1) occurs when a species separates into two separate groups which are isolated from one another. A physical barrier, such as a mountain range or a waterway, makes it impossible for them to breed with one another.

What are 2 mechanisms that promote speciation after Allopatric separation?

Two mechanisms of speciation are allopatric (“other fatherland”) and sympatric (“together in the fatherland”) forms. In both cases, a single population divides into two, and heritable differences eventually prevent gene flow between the two through reproductive isolation.

Is gene flow necessary for speciation?

Allopatry may start the process off, but the evolution of internal (i.e., genetically-based) barriers to gene flow is necessary for speciation to be complete. If internal barriers to gene flow do not evolve, individuals from the two parts of the population will freely interbreed if they come back into contact.

Does reduced gene flow always result in speciation?

Even in the absence of a geographic barrier, reduced gene flow across a species' range can encourage speciation.

Can species be maintained without gene flow?

- Species can be maintained without gene flow. ... According to the ecological species concept, species boundaries can be maintained even when substantial amounts of gene flow occur between species. This is seen in populations that have ____ hybrid individuals than non-hybrid individuals.