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 A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

exists at comparable

latitude In geography, latitude is a geographic coordinate system, geographic 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 t ...

s across the

equator The equator is the circle of latitude that divides Earth into the Northern Hemisphere, Northern and Southern Hemisphere, Southern Hemispheres of Earth, hemispheres. It is an imaginary line located at 0 degrees latitude, about in circumferen ...

but not in the

tropics The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

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

Tropic of Cancer The Tropic of Cancer, also known as the Northern Tropic, is the Earth's northernmost circle of latitude where the Sun can be seen directly overhead. This occurs on the June solstice, when the Northern Hemisphere is tilted toward the Sun ...

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 reach ...

, 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'' – American Bowlesia * '' Osmorhiza berteroi'' and '' Osmorhiza depauperata'' – sweet cecily species. * ''

Ruppia megacarpa ''Ruppia megacarpa'' is a submerged herb species in the genus ''Ruppia ''Ruppia'', also known as the widgeonweeds, ditch grasses or widgeon grass, is the only extant genus in the family Ruppiaceae, with 11 known species. These are aquatic pl ...

'' * '' Solenogyne'' *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 ''Scylla serrata'' (often called mud crab or mangrove crab, although both terms are highly ambiguous, and black crab) is an ecologically important species of crab found in the estuaries and mangroves of Africa, Australia, and Asia. In their ...

'' – mud crab * Freshwater crayfish * Ground beetle genus '' Bembidion''

Bryophytes and lichens

* '' Tetraplodon fuegianus'' - dung moss

References

Biogeography {{Ecology-stub

Known cases

Plants

Animals

Bryophytes and lichens

See also

References