Nearctic
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The Nearctic realm is one of the eight biogeographic realms constituting the Earth's land surface. The Nearctic realm covers most of
North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
, including
Greenland Greenland is an autonomous territory in the Danish Realm, Kingdom of Denmark. It is by far the largest geographically of three constituent parts of the kingdom; the other two are metropolitan Denmark and the Faroe Islands. Citizens of Greenlan ...
,
Central Florida Central Florida is a Regions of the United States#Florida, region of the U.S. state of Florida. Different sources give different definitions for the region, but as its name implies it is usually said to comprise the central part of the state, in ...
, and the highlands of
Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...
. The parts of North America that are not in the Nearctic realm include most of coastal Mexico, southern Mexico, southern Florida, coastal central
Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...
,
Central America Central America is a subregion of North America. Its political boundaries are defined as bordering Mexico to the north, Colombia to the southeast, the Caribbean to the east, and the Pacific Ocean to the southwest. Central America is usually ...
,
Bermuda Bermuda is a British Overseas Territories, British Overseas Territory in the Atlantic Ocean, North Atlantic Ocean. The closest land outside the territory is in the American state of North Carolina, about to the west-northwest. Bermuda is an ...
and the
Caribbean The Caribbean ( , ; ; ; ) is a region in the middle of the Americas centered around the Caribbean Sea in the Atlantic Ocean, North Atlantic Ocean, mostly overlapping with the West Indies. Bordered by North America to the north, Central America ...
islands. Together with
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...
, these regions are part of the
Neotropical realm The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropics, tropical Ecoregion#Terrestrial, terrestrial ecoregions of the Americas and the entire South American temperat ...
.


Major ecological regions

The World Wildlife Fund (WWF) divides the Nearctic into four bioregions, defined as "geographic clusters of ecoregions that may span several habitat types, but have strong biogeographic affinities, particularly at taxonomic levels higher than the species level (genus, family)."


Canadian Shield

The Canadian Shield bioregion extends across the northern portion of the continent, from the Aleutian Islands to Newfoundland. It includes the Nearctic's arctic tundra and boreal forest ecoregions. In terms of floristic provinces, it is represented by part of the Canadian Province of the Circumboreal Region.


Eastern North America

The Eastern North America bioregion includes the temperate broadleaf and mixed forests of the Eastern United States and southeastern Canada, the
Great Plains The Great Plains is a broad expanse of plain, flatland in North America. The region stretches east of the Rocky Mountains, much of it covered in prairie, steppe, and grassland. They are the western part of the Interior Plains, which include th ...
temperate grasslands of the central United States and south-central Canada, the temperate coniferous forests of the southeastern United States, including
central Florida Central Florida is a Regions of the United States#Florida, region of the U.S. state of Florida. Different sources give different definitions for the region, but as its name implies it is usually said to comprise the central part of the state, in ...
. In terms of floristic provinces, it is represented by the North American Atlantic Region and part of the Canadian Province of the Circumboreal Region.


Western North America

The Western North America bioregion includes the temperate coniferous forests of the coastal and mountain regions of southern Alaska, western Canada, and the western United States from the Pacific Coast and
Northern California Northern California (commonly shortened to NorCal) is a geocultural region that comprises the northern portion of the U.S. state of California, spanning the northernmost 48 of the state's List of counties in California, 58 counties. Northern Ca ...
to the Rocky Mountains (known as the Cascadian bioregion), as well as the cold-winter intermountain
deserts and xeric shrublands Deserts and xeric shrublands are a biome defined by the World Wide Fund for Nature. Deserts and xeric (Ancient Greek 'dry') shrublands form the largest terrestrial biome, covering 19% of Earth's land surface area. Ecoregions in this habitat ...
and temperate grasslands and shrublands of the Western United States. In terms of floristic provinces, it is represented by the Rocky Mountain region.


Northern Mexico

The Northern Mexico bioregion includes the mild-winter to cold-winter deserts and xeric shrublands, warm temperate and subtropical pine and pine-oak forests, and Mediterranean climate ecoregions of the Mexican Plateau, Baja California peninsula, and the southwestern United States, bordered to the south by the Neotropical Trans-Mexican Volcanic Belt. This region also includes the only subtropical dry broadleaf forest in the Nearctic realm, the Sonoran–Sinaloan transition subtropical dry forest. In terms of floristic provinces, it is represented by the Madrean Region.


History

Although North America and South America are presently joined by the Isthmus of Panama, these continents were separated for about 180 million years, and evolved very different plant and animal lineages. When the ancient supercontinent of Pangaea split into two about 180 million years ago, North America remained joined to
Eurasia Eurasia ( , ) is a continental area on Earth, comprising all of Europe and Asia. According to some geographers, Physical geography, physiographically, Eurasia is a single supercontinent. The concept of Europe and Asia as distinct continents d ...
as part of the supercontinent of Laurasia, while South America was part of the supercontinent of Gondwana. North America later split from Eurasia. North America has been joined by land bridges to both
Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...
and South America since then, which allowed an exchange of plant and animal
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), ...
between the continents, the Great American Interchange. A former land bridge across the Bering Strait between Asia and North America allowed many plants and animals to move between these continents, and the Nearctic realm shares many plants and animals with the
Palearctic The Palearctic or Palaearctic is a biogeographic realm of the Earth, the largest of eight. Confined almost entirely to the Eastern Hemisphere, it stretches across Europe and Asia, north of the foothills of the Himalayas, and North Africa. Th ...
. The two realms are sometimes included in a single Holarctic realm. Many large animals, or megafauna, including
horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 mi ...
s, camels, tapirs, mammoths, mastodons, ground sloths, sabre-tooth cats ('' Smilodon''), short-faced bears and the American cheetah, became extinct in North America at the end of the
Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...
epoch (ice ages) in what is called the Quaternary extinction event.


Flora and fauna


Flora and fauna that originated in the Nearctic

Mammals originally unique to the Nearctic include: * Order
Primate Primates is an order (biology), order of mammals, which is further divided into the Strepsirrhini, strepsirrhines, which include lemurs, galagos, and Lorisidae, lorisids; and the Haplorhini, haplorhines, which include Tarsiiformes, tarsiers a ...
s – the first primate/proto-primate, '' Purgatorius'', originated in the
Early Paleocene The Danian is the oldest age (geology), age or lowest stage (stratigraphy), stage of the Paleocene Epoch or series (stratigraphy), Series, of the Paleogene Period or system (stratigraphy), System, and of the Cenozoic Era or Erathem. The beginnin ...
of the Nearctic. * Family
Canidae Canidae (; from Latin, ''canis'', "dog") is a family (biology), biological family of caniform carnivorans, constituting a clade. A member of this family is also called a canid (). The family includes three subfamily, subfamilies: the Caninae, a ...
dogs, wolves, foxes, and coyotes. * Family Camelidaecamels and their South American relatives including the
llama The llama (; or ) (''Lama glama'') is a domesticated South American camelid, widely used as a List of meat animals, meat and pack animal by Inca empire, Andean cultures since the pre-Columbian era. Llamas are social animals and live with ...
. Now extinct in the Nearctic * Family Equidae
horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 mi ...
s,
donkey The donkey or ass is a domesticated equine. It derives from the African wild ass, ''Equus africanus'', and may be classified either as a subspecies thereof, ''Equus africanus asinus'', or as a separate species, ''Equus asinus''. It was domes ...
s and their relatives. Now only found in the Nearctic as feral horses. * Family Tapiridaetapirs now extinct in the Nearctic. * Family Antilocapridae – last survivor of which is the pronghorn. * Subfamily Tremarctinae (short-faced
bear Bears are carnivoran mammals of the family (biology), family Ursidae (). They are classified as caniforms, or doglike carnivorans. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of habitats ...
s) – including the giant short-faced bear ('' Arctodus simus''). The only surviving member of the group is the spectacled bear (''Tremarctos ornatus'') of South America.


Flora and fauna endemic to the Nearctic

Two
mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...
families are endemic to the Nearctic, the pronghorns ( Antilocapridae) and the mountain beaver ( Aplodontiidae). The Holarctic has four endemic families of birds: divers (Gaviidae), grouse (Tetraoninae),
auk Auks or alcids are birds of the family Alcidae in the order Charadriiformes. The alcid family includes the Uria, murres, guillemots, Aethia, auklets, puffins, and Brachyramphus, murrelets. The family contains 25 extant or recently extinct speci ...
s (Alcidae), and the waxwings (Bombycillidae). The scarab beetle families Pleocomidae and Diphyllostomatidae ( Coleoptera) are also endemic to the Nearctic. The fly species '' Cynomya cadaverina'' is also found in high numbers in this area. Plant families endemic or nearly endemic to the Nearctic include the Crossosomataceae, Simmondsiaceae, and Limnanthaceae.


Nearctic terrestrial ecoregions


See also

* List of ecoregions in Canada (WWF) * List of ecoregions in Mexico (WWF) * List of ecoregions in the United States (WWF)


References

* Abell, R.A. et al. (2000). ''Freshwater Ecoregions of North America: A Conservation Assessment'' Washington, DC: Island Press
Freshwater Ecoregions of North America: A Conservation Assessment
* Flannery, Tim (2001). ''The Eternal Frontier: an Ecological History of North America and its Peoples''. Grove Press, New York. * Ricketts, Taylor H., Eric Dinerstein, David M. Olson, Colby J. Loucks, et al. (1999). ''Terrestrial Ecoregions of North America: a Conservation Assessment''. Island Press, Washington DC.
Terrestrial Ecoregions of North America: A Conservation Assessment


External links


Map of the ecozones

Nearctica, The Natural World of North America
* {{Authority control Biogeographic realms