Biotic interchange is the process by which species from one biota invade another biota, usually due to the disappearance of a previously impassable barrier. These dispersal barriers can be physical, climatic, or biological and can include bodies of water or ice, land features like mountains, climate zones, or competition between species. Biotic interchange has been documented to occur in marine, freshwater, and terrestrial environments.

Causes

The general cause of a biotic interchange is the disappearance of a barrier that had been previously blocking the dispersal of species from two distinct biotas. The disappearance of a barrier could be from the closing of a sea, connecting two previously unconnected continents; the melting of

glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its Ablation#Glaciology, ablation over many years, often Century, centuries. It acquires dis ...

s, allowing for migration across newly exposed areas that had been covered by ice; from sea level change, covering a land bridge would allow for marine interchange, while revealing a land bridge would allow for terrestrial interchange; and, it could also be from changing

ocean current An ocean current is a continuous, directed movement of sea water generated by a number of forces acting upon the water, including wind, the Coriolis effect, breaking waves, cabbeling, and temperature and salinity differences. Depth contours, s ...

s, allowing for larval dispersal to new territories. Ontario_Highway_401_(31782980771)

Humans have also become a vector of biotic interchange. They have fragmented species habitat by blocking interchange in some regions. Yet, humans have also intentionally and unintentionally spread many

non-native species An introduced species, alien species, exotic species, adventive species, immigrant species, foreign species, non-indigenous species, or non-native species is a species living outside its native distributional range, but which has arrived there ...

around the globe. Climate change may also be impacting the effectiveness of natural dispersal barriers.

Effects

Sometimes an interchange can result in the

extinction Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

of some species. These species may go extinct due to the introduction of a predator that they are not adapted to, or due to more successful

competition Competition is a rivalry where two or more parties strive for a common goal which cannot be shared: where one's gain is the other's loss (an example of which is a zero-sum game). Competition can arise between entities such as organisms, indivi ...

by invading species. However, invading species can coexist with native species for millions of years after an invasion. Sometimes invading species can also improve

biodiversity Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...

by increasing genetic diversity. Another effect of biotic interchange is

homogenization Homogeneity is a sameness of constituent structure. Homogeneity, homogeneous, or homogenization may also refer to: In mathematics *Transcendental law of homogeneity of Leibniz * Homogeneous space for a Lie group G, or more general transformati ...

. This occurs when many invading species from both biotas become established, creating one similar biota.

Asymmetry

Many of the biotic interchanges studied have shown an asymmetry in the sharing of species between two biotas. Typically there is a donator biota and a recipient biota, with the donator biota sharing more species than the recipient biota. As an example, when the

Suez Canal The Suez Canal ( arz, قَنَاةُ ٱلسُّوَيْسِ, ') is an artificial sea-level waterway in Egypt, connecting the Mediterranean Sea to the Red Sea through the Isthmus of Suez and dividing Africa and Asia. The long canal is a popular ...

connected the

Red Sea The Red Sea ( ar, البحر الأحمر - بحر القلزم, translit=Modern: al-Baḥr al-ʾAḥmar, Medieval: Baḥr al-Qulzum; or ; Coptic: ⲫⲓⲟⲙ ⲛ̀ϩⲁϩ ''Phiom Enhah'' or ⲫⲓⲟⲙ ⲛ̀ϣⲁⲣⲓ ''Phiom ǹšari''; T ...

and

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ea ...

, most new species in the Mediterranean originated in the Red Sea (91 molluscs, 15 crabs, and 41 fish). Fewer species travelled from the Mediterranean into the Red Sea (3 molluscs, 0 crabs, and 6 fish). Invading species from the donator biota are often only a small percent of the potential invaders available within that biota. That is to say, that not all species that could invade another biota do invade. For example, only about 4.3% of the total fish species in the Red Sea have actually invaded the Mediterranean.

Hypotheses

There are many hypothesis that attempt to explain the asymmetry and general processes involved in biotic interchange: * The null hypothesis suggests that the number of species invading a recipient biota should be proportional to the number of species available in the donator biota. However, comparisons of many biotic interchanges reveal that this is not true. * The hypothesis of ecological opportunity suggests that the number of species invading a recipient biota should be proportional to the number of species that go extinct in the recipient biota. * The biogeographic superiority hypothesis suggests that over time the species in one region would evolve superiority over species in a different region, and would thus be better at invading. * The universal trade off hypothesis suggests that species with similar life habits separated for long periods of

geologic time The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochrono ...

may still be able to coexist if brought back together due to the presence of similar evolutionary pressures affecting their past adaptation to their surroundings.

Past

During the Trans-Arctic Interchange (,

Early Pliocene Early may refer to: History * The beginning or oldest part of a defined historical period, as opposed to middle or late periods, e.g.: ** Early Christianity ** Early modern Europe Places in the United States * Early, Iowa * Early, Texas * Early ...

) sea levels rose, submerging the Bering Strait, and allowing marine organisms from the North Pacific and

North Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Africa, Europe and ...

Arctic Ocean The Arctic Ocean is the smallest and shallowest of the world's five major oceans. It spans an area of approximately and is known as the coldest of all the oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, a ...

to come into contact with each other. During the

Great American Interchange The Great American Biotic Interchange (commonly abbreviated as GABI), also known as the Great American Interchange and the Great American Faunal Interchange, was an important late Cenozoic paleozoogeographic biotic interchange event in which lan ...

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58 The Indian Subcontinent and Mainland Asia Interchange (

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

) was the collision of the

Indian Plate The Indian Plate (or India Plate) is a minor tectonic plate straddling the equator in the Eastern Hemisphere. Originally a part of the ancient continent of Gondwana, the Indian Plate broke away from the other fragments of Gondwana , began mov ...

with mainland Asia allowing for biotic interchange mainly from mainland Asia onto the Indian subcontinent. Bering Land Bridge Interchange (late

Cenozoic The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configura ...

) was an interchange between Asian and North American land species across the Bering land bridge. The African and Eurasian Interchange (, early

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

) occurred between Africa and Eurasia through the Middle East after the Tethys sea closed.

Present

The Trans-Suez Interchange is a human-induced biotic interchange between the Mediterranean and the Red Sea due to the construction of the

Suez canal The Suez Canal ( arz, قَنَاةُ ٱلسُّوَيْسِ, ') is an artificial sea-level waterway in Egypt, connecting the Mediterranean Sea to the Red Sea through the Isthmus of Suez and dividing Africa and Asia. The long canal is a popular ...

. Another human-induced biotic interchange, the Japan–North American Interchange, is between marine species off the coast of Japan and North America. These species are transported as larvae in ships' ballast. The Panama Canal Interchange between the eastern Pacific and western Atlantic oceans through the

Panama Canal The Panama Canal ( es, Canal de Panamá, link=no) is an artificial waterway in Panama that connects the Atlantic Ocean with the Pacific Ocean and divides North and South America. The canal cuts across the Isthmus of Panama and is a conduit ...

. This interchange has been relatively minimal due to the canal containing freshwater.

References

{{Reflist Biogeography