Name: how new species form
Uploaded: 2026-06-01T06:28:05.158Z
Duration: 1 min 31 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

NC K-12 Science Standard Course of Study

9-12

Biology

Biological Evolution- Unity and Diversity

LS.Bio.9.1

Formation of Species

Speciation occurs when a species splits into two or more new species, usually due to geographic isolation and genetic divergence. Over time, these factors result in populations that can no longer successfully breed with each other. This happens through two primary mechanisms: allopatric and sympatric speciation.In allopatric speciation, the formation of a geographic barrier, like a mountain range, can cut off gene flow between two populations. Once they are separated, different climates, food sources, or predators can act as selective pressures. Over time, evolutionary processes such as natural selection and genetic drift can lead these populations to evolve into separate species.This mechanism may also happen when a small group splits off, like birds that fly to a new island. This is known as a founder event, a common form of allopatric speciation. Over time, they undergo natural selection in the new environment, which stops gene flow between the two populations.But reproductive isolation that leads to speciation does not require a geographic barrier.In sympatric speciation, new species form within the same geographic area when groups within a population stop breeding with each ot

formation of species

Speciation describes the formation of one or more new species from one or sometimes multiple original species. The resulting species are discrete from the parent species, and barriers to reproduction will typically exist. There are two primary mechanisms, speciation with and without geographic isolation&#x2014;allopatric and sympatric speciation, respectively.<h4>Allopatric Speciation</h4>In allopatric speciation, gene flow between two populations of the same species is prevented by a geographic barrier, like a mountain range or habitat fragmentation. This is known as vicariance. For example, a drought may cause the water levels in a large lake to drop, leaving two or more smaller bodies of water in which the inhabitants are cut off from one another.Once in isolation, the individuals in these populations may face different external pressures, such as climate, resource availability or predation. These differences in natural selection combined with genetic drift and mutation over many generations of separation eventually result in the two populations becoming discrete species. This has been observed in lakes containing African cichlid fish, which display a vast array of species, many of which likely evolved due to allopatry.Dispersal can also produce allopatric speciation. For example, the parasitic sea anemone species Edwardsiella lineata lives on the east coast of North America. It has a closely related sister species, E. carnea, which inhabits the oceans of the Swedish and Norwegian coasts. Dispersal of E. lineata&#x2014;likely carried in their larval stage as parasites in comb jellies&#x2014;may have led to the establishment of a new population on the Scandinavian coast. This new and genetically isolated population then diverged over time to become a separate species now known as E. carnea.<h4>Sympatric Speciation</h4>Speciation can also occur without geographic barriers. For example, some crater lakes in Iceland contain multiple novel closely related fish species which almost certainly evolved in sympatry because geographic isolation is impossible due to the shape of their habitat. However, sympatric speciation is arguably harder to achieve. In sympatry, the member species still come into contact with one another and potentially interbreed and exchange genes. Chromosome recombination would likely occur frequently, at least in the beginning of the separation, and break up groups of co-adapted genes needed for the formation of new species. Although less common than allopatric speciation, there are examples of genetic divergence and speciation in sympatry. Changes are driven by factors such as habitat differentiation, sexual selection, and polyploidy, which create barriers to the exchange of genetic information.Sympatric speciation can occur when subsets of a species evolve to exploit different habitats or resources in the same geographical area. For example, subspecies of the medium ground finch, Geospiza fortis, found on Santa Cruz Island in the Galapagos show signs of genetic divergence based on beak size. The beak morphology in this species conforms to two different size ideals&#x2014;small and large&#x2014;based on the size and hardness of seeds they specialized in consuming (an example of habitat differentiation). However, owing to natural selection, birds with intermediate beak sizes were selected against because they survived at lower rates.New species may also be created through polyploidy&#x2014;a mechanism that is relatively common in plants. Usually, this is caused by random errors during cell division resulting in extra sets of chromosomes. The polyploid hybrids thus produced will likely be unable to mate with the diploid parental lines, and instead, produce fertile offspring through self-pollination or by mating with other polyploid hybrids. Therefore, such polyploid speciation can generate new plant species in a single generation. Analyses suggest that 47% to 100% of flowering plant species can be traced back to a polyploidy event at some point in their evolutionary history.

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Education

JoVE Core

Evolution

Speciation and Diversity

KEY TERMS AND CONCEPTS

how new species form

Speciation is the process that creates new species from one original species or from multiple original species. The new species become separate from the parent species, and barriers to reproduction usually develop. The main routes are allopatric speciation, which happens with geographic isolation, and sympatric speciation, which happens without it.

In allopatric speciation, gene flow between two populations is blocked by a geographic barrier such as a mountain range or habitat fragmentation. This is called vicariance. A drought can also split a large lake into smaller bodies of water, leaving populations cut off from one another. Once isolated, the groups may face different climate, resource, and predation pressures. Over many generations, natural selection, genetic drift, and mutation can make the populations distinct species. African cichlid fish from lakes are a well-known example, and many of their species likely formed this way.

Allopatric speciation can also happen through dispersal. The sea anemone Edwardsiella lineata lives on the east coast of North America, while its sister species, E. carnea, lives off the Swedish and Norwegian coasts. The North American species may have been carried in its larval stage by comb jellies to Scandinavia. That new population became genetically isolated and later diverged into a separate species.

Speciation can also occur without a geographic barrier. Some crater lakes in Iceland contain several closely related fish species that likely evolved in sympatry because the habitat shape makes geographic isolation impossible. Sympatric speciation is harder because the groups still meet, may interbreed, and can exchange genes. Early on, chromosome recombination can break up co-adapted gene groups needed for new species to form.

Even so, sympatric speciation can happen through habitat differentiation, sexual selection, and polyploidy. In the Galapagos, medium ground finches on Santa Cruz Island show divergence in beak size based on the seeds they eat. Small and large beaks match different seed types, while birds with intermediate beak sizes were selected against because they survived less well. In plants, polyploidy can create new species when cell division errors produce extra chromosome sets. The polyploid hybrids may not mate with the diploid parent lines, but they can produce fertile offspring through self-pollination or with other polyploid hybrids. This can create a new plant species in a single generation, and studies suggest that 47% to 100% of flowering plant species trace back to a polyploidy event.

How New Species Form

understanding species and reproductive barriers

How Species Stay Genetically Separate

Species stay genetically separate through reproductive barriers that limit mating, fertilization, or the survival of offspring. A species is a group of organisms that can interbreed and produce fertile offspring. Members of the same species often look alike because they share very similar genomes. Even so, some organisms that look similar are not the same species. Variation within a species is common. The common wall lizard, Podarcis muralis, has six morphs that differ in throat and underbelly...

Speciation is the process that creates new species from one original species or from multiple original species. The new species become separate from the parent species, and barriers to reproduction usually develop. The main routes are allopatric speciation, which happens with geographic isolation, and sympatric speciation, which happens without it. In allopatric speciation, gene flow between two populations is blocked by a geographic barrier such as a mountain range or habitat fragmentation.

genetics of speciation

Reproductive Barriers in Speciation

Reproductive barriers drive speciation by stopping gene flow between populations. Speciation is the evolutionary process that forms new, distinct species, which are groups that cannot freely reproduce with one another. The genetics behind this process focuses on traits and isolating mechanisms that keep populations reproductively isolated. Some barriers act before a zygote forms, and these are called pre-zygotic mechanisms. They prevent fertilization and create the strongest block to gene flow...

speciation rates

Two Paths to New Species

Speciation can happen at different speeds, and evolutionary biologists describe those patterns with gradualism and punctuated equilibrium. Both models explain how new species arise. They also show that evolutionary change comes from heritable variation in a population, with natural selection often favoring traits that help survival and reproduction in a given environment. Gradualism is the slow, steady path to speciation. Small changes build up over many generations. In one example, birds on...

hybrid zones

How Hybrid Zones Shape Species Change

Hybrid zones are narrow regions where two closely related species meet, mate, and produce hybrids. Hybrids can show different traits or genes from either parent species. Those differences can affect survival and reproductive success. Because of this, hybridization can change species diversity and influence speciation within the hybrid zone. Gene flow and natural selection shape what happens in a hybrid zone. Gene flow moves genes between populations and can spread, blend, and preserve genetic...

key terms and concepts

Explore allopatric and sympatric speciation, with examples from cichlid fish, finches, sea anemones, and polyploid plants.

How New Species Form | JoVE K12

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biology

LS.Bio.10.1

Pennsylvania State Academic Standards

Life Science

interdependent-relationships-in-ecosystems

Interdependent Relationships in Ecosystems

3.1.9-12.V

Natural Selection and Evolution

3.1.9-12.X

Louisiana Student Standards for Science

High School

Life Sciences

Biological Evolution: Unity And Diversity

HS-LS4-5

Environmental Science

ecosystems-interactions-energy-and-dynamics

Ecosystems: Interactions, Energy And Dynamics

HS-LS2-7

Virginia  Standards of Learning

HIgh School

LS.11

LS.11.a

Minnesota Academic Standards in Science

4.1.1 9L.4.1.1.1

new-jersey-student-learning-standards-for-science

New Jersey Student Learning Standards for Science

Biological Evolution: Unity and Diversity

Arizona Science Standards

HS.L4

HS.L4U1.27

Next Generation Science Standards

heredity-inheritance-and-variation-of-traits

Heredity: Inheritance and Variation of Traits

HS-LS4-3

Earth and Space Science

Earth’s Systems

HS-ESS2-6

Florida Department of Education

SC.912.L.15

SC.912.L.15.9

Texas Essential Knowledge and Skills

BIO.10

BIO.10.C

south-carolina-college-and-career-ready-science-standards

South Carolina College and Career Ready Science Standards

B-LS4-2.

B-LS4-5.

new-york-state-science-learning-standards

New York State Science Learning Standards

HS-LS4-3.

HS-LS4-5.

Earth and Space Sciences

HS-ESS2-7.

Georgia Standards of Excellence

Ecology

SEC3.

SEC3.d

SB6.b

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Understanding Species and Reproductive Barriers

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Speciation Rates

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Genetics of Speciation

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Hybrid Zones

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What is Natural Selection?

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LS.Bio.9.2

Use models to illustrate the conditions required for natural selection, including the overproduction of offspring, inherited variation, and the struggle to survive.

LS.Bio.9.3

Construct an explanation to explain how natural selection leads to adaptations within populations.

LS.Bio.9.4

Extinction

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Use models (including dichotomous keys, scientific nomenclature, cladograms, phylogenetic trees) to identify organisms and exemplify relationships.

LS.Bio.10.2

Understand natural selection as a mechanism for biological evolution.

How New Species Form

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