Antitropical (alternatives include biantitropical or amphitropical) distribution is a type of

disjunct distribution In biology, a taxon with a disjunct distribution is one that has two or more groups that are related but considerably separated from each other geographically. The causes are varied and might demonstrate either the expansion or contraction of a s ...

where a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...

exists at comparable

latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north ...

s across the

equator The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can also ...

but not in the

tropics The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also refer ...

. For example, a species may be found north of the

Tropic of Cancer The Tropic of Cancer, which is also referred to as the Northern Tropic, is the most northerly circle of latitude on Earth at which the Sun can be directly overhead. This occurs on the June solstice, when the Northern Hemisphere is tilted towa ...

and south of the

Tropic of Capricorn The Tropic of Capricorn (or the Southern Tropic) is the circle of latitude that contains the subsolar point at the December (or southern) solstice. It is thus the southernmost latitude where the Sun can be seen directly overhead. It also reac ...

, but not in between. With increasing time since dispersal, the disjunct populations may be the same variety, species, or clade. How the life forms distribute themselves to the opposite hemisphere when they can't normally survive in the middle depends on the species; plants may have their seed spread through wind, animal, or other methods and then germinate upon reaching the appropriate climate, while sea life may be able to travel through the tropical regions in a larval state or by going through deep ocean currents with much colder temperatures than on the surface. For the American amphitropical distribution, dispersal has been generally agreed to be more likely than

vicariance Allopatric speciation () – 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 ...

from a previous distribution including the tropics in North and South America.

Known cases

Plants

* '' Phacelia crenulata'' – scorpionweed * ''

Bowlesia incana ''Bowlesia incana'' is a species of flowering plant in the family Apiaceae known by the common name hoary bowlesia. It is native to South America and the southeastern and southwestern United States as far north as Oregon. It can also be found in ...

'' – American Bowlesia * ''

Osmorhiza berteroi ''Osmorhiza berteroi'' is a species of flowering plant in the family Apiaceae known by the common name mountain sweet cicely. Systematics ''Osmorhiza berteroi'' forms a species complex together with '' O. depauperata'' and '' O. purpurea''. Un ...

'' and ''

Osmorhiza depauperata ''Osmorhiza depauperata'' is a species of flowering plant in the carrot family known by the common names bluntseed sweetroot and blunt-fruited sweet-cicely. Distribution and habitat The plant is native to much of western and northern North Amer ...

'' – sweet cecily species. * ''

Ruppia megacarpa ''Ruppia megacarpa'' is a submerged herb species in the genus '' Ruppia'' found in shallow brackish waters. It is a common on Australasian coasts, including Australia (NSW; SA; Vic Vic (; es, Vic or Pancracio Celdrán (2004). Diccionario ...

'' * ''

Solenogyne ''Solenogyne'' is a genus of Australian plants in the tribe Astereae within the family Asteraceae.Cassini, Alexandre Henri Gabriel de. 1828. Dictionnaire des Sciences Naturelles [Second edition/nowiki> 56: 174-176">econd edition">Cassini, Alexan ...

'' *For a list of American amphitropically distributed plants (237 vascular plants), see the tables in the open access paper Simpson et al. 2017 or their working group on figshare

Animals

* ''Scylla serrata'' – mud crab * Crayfish, Freshwater crayfish * Ground beetle genus ''Bembidion''

Bryophytes and lichens

* ''Tetraplodon (plant), Tetraplodon fuegianus'' - dung moss

References

Biogeography {{Ecology-stub

Known cases

Plants

Animals

Bryophytes and lichens

See also

References