The Madrean Region (named after the

Sierra Madre Occidental The Sierra Madre Occidental is a major mountain range system of the North American Cordillera, that runs northwest–southeast through northwestern and western Mexico, and along the Gulf of California. The Sierra Madre is part of the American ...

) is a

floristic region A phytochorion, in phytogeography, is a geographic area with a relatively uniform composition of plant species. Adjacent phytochoria do not usually have a sharp boundary, but rather a soft one, a transitional area in which many species from both re ...

within the Holarctic Kingdom in North America, as delineated by Armen Takhtajan and Robert F. Thorne. It occupies arid or semiarid areas in the southwestern

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...

and northwestern

Mexico Mexico ( Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guate ...

and is bordered by the Rocky Mountain Region and North American Atlantic Region of the Holarctic Kingdom in the north and in the east, Caribbean Region of the Neotropical Kingdom in the south. The Madrean Region is characterized by a very distinct

flora Flora (: floras or florae) is all the plant life present in a particular region or time, generally the naturally occurring (indigenous (ecology), indigenous) native plant, native plants. The corresponding term for animals is ''fauna'', and for f ...

with at least three

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found els ...

families (

Fouquieriaceae ''Fouquieria'' is a genus of 11 species of desert plants, the sole genus in the Family (biology), family Fouquieriaceae. The genus includes the ocotillo (''Fouquieria splendens, F. splendens'') and the Boojum tree or cirio (''Fouquieria columnar ...

, Simmondsiaceae, and Setchellanthaceae). Crossosomataceae, Garryaceae, Lennoaceae, Limnanthaceae and Stegnospermataceae have their principal development here; for

Onagraceae The Onagraceae are a family of flowering plants known as the willowherb family or evening primrose family. They include about 650 species of herbs, shrubs, and trees Polemoniaceae The Polemoniaceae (Jacob's-ladder or phlox family) are a family of flowering plants consisting of about 25 genera with 270–400 species of annuals and perennials native to the Northern Hemisphere and South America, with the center of diversity ...

and Hydrophyllaceae it is the major center of diversity. More than 250

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial ...

and probably more than half of the

species In biology, a species is the basic unit of Taxonomy (biology), 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 ...

of the region are

to it according to Takhtajan.

Floristic provinces

The region is subdivided into four floristic provinces: * Great Basin Province * Californian Province *Sonoran Province * Mexican Highlands Province

Great Basin Province

The Great Basin Floristic Province includes most of the Great Basin, as well as the

Colorado Plateau The Colorado Plateau, also known as the Colorado Plateau Province, is a physiographic and desert region of the Intermontane Plateaus, roughly centered on the Four Corners region of the southwestern United States. This province covers an area ...

, the

Snake River Plain The canyons">Snake River cutting through the plain leaves many canyons and Canyon#List of gorges">gorges, such as this one near Twin Falls, Idaho The Snake River Plain is a geologic feature located primarily within the U.S. state of Idaho ...

, and Arizona north of the

Mogollon Rim The Mogollon Rim ( or or ) is a topographical and geological feature cutting across the northern half of the U.S. state of Arizona. It extends approximately , starting in northern Yavapai County and running eastward, ending near the borde ...

. It shares much of its flora with the neighboring provinces and has only a few endemic

Species In biology, a species is the basic unit of Taxonomy (biology), 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 ...

endemism is also moderate (about 25%), but is much more considerable in such genera as ''

Astragalus ''Astragalus'' is a large genus of over 3,000 species of herbs and small shrubs, belonging to the legume family Fabaceae and the subfamily Faboideae. It is the largest genus of plants in terms of described species. The genus is native to te ...

'', '' Eriogonum'', ''

Penstemon ''Penstemon'' , the beardtongues, is a large genus of roughly 250 species of flowering plants native mostly to the Nearctic, but with a few species also found in the North American portion of the Neotropics. It is the largest genus of flowering ...

'', '' Cymopterus'', ''

Lomatium ''Lomatium'' is a genus in the family Apiaceae. It consists of about 100 species native to western Northern America and northern Mexico. Its common names include biscuitroot, Indian parsley, and desert parsley. It is in the family Apiaceae a ...

'', '' Cryptantha'', ''

Chrysothamnus ''Chrysothamnus'', known as rabbitbrush, rabbitbush, and chamisa, are a genus of shrubs in the family Asteraceae. The native distribution is in the arid western United States, Canada, and northern Mexico. It is known for its bright white or ...

'', '' Erigeron'', ''

Phacelia ''Phacelia'' (phacelia, scorpionweed, heliotrope) is a genus of about 200 species of annual or perennial herbaceous plants in the borage family, native to North and South America. California is particularly rich in species with over 90 record ...

'', '' Castilleja'', and ''

Gilia ''Gilia'' is a genus of between 25 and 50 species of flowering plants in the Polemoniaceae family and is related to phlox. These Western native plants are best sown in sunny, well-draining soil in the temperate and tropical regions of the Amer ...

''. The vegetation in the central Great Basin shrub steppe part of the province is dominated by '' Artemisia'' species and

Chenopodiaceae Amaranthaceae is a family of flowering plants commonly known as the amaranth family, in reference to its type genus '' Amaranthus''. It includes the former goosefoot family Chenopodiaceae and contains about 165 genera and 2,040 species, making it ...

genera. The Great Basin montane forests include ancient

Great Basin bristlecone pine ''Pinus longaeva'' (commonly referred to as the Great Basin bristlecone pine, intermountain bristlecone pine, or western bristlecone pine) is a long-living species of bristlecone pine tree found in the higher mountains of California, Nevada, and ...

(''Pinus longaeva'') trees.

Californian Province

The Californian Province occupies Central and Southern

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the ...

from the seashore to the foothills of the Cascade Range, the

Sierra Nevada The Sierra Nevada () is a mountain range in the Western United States, between the Central Valley of California and the Great Basin. The vast majority of the range lies in the state of California, although the Carson Range spur lies primari ...

range, and northern parts of

Baja California Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...

. It possesses the most diverse flora within the floristic region. About half of the species are endemic. More than 50 genera (e.g. '' Adenostoma'', '' Bergerocactus'', ''

Carpenteria ''Carpenteria'' , the tree anemone or bush anemone, is a genus of flowering plants in the hydrangea family Hydrangeaceae. It is closely related to the similar genus ''Philadelphus'' and is monotypic, being represented by the single species ''C ...

'', ''

Cneoridium ''Cneoridium'' is a monotypic genus in the citrus family which contains the single species ''Cneoridium dumosum'', commonly known as bushrue or coast spice bush. This perennial, evergreen shrub is native to the coast of southern California and B ...

'', '' Dendromecon'', ''

Fremontodendron ''Fremontodendron'', with the common names fremontia and flannelbush or flannel bush, is a genus of three known species of shrubs native plant, native to the Southwestern United States and northwest Mexico. Taxonomy They are within the botanical ...

'', ''

Jepsonia ''Jepsonia'' is a small genus of flowering plants containing three species. The ''Jepsonia'' is a perennial with a cormlike caudex A caudex (plural: caudices) of a plant is a stem, but the term is also used to mean a rootstock and particularly ...

'', '' Lyonothamnus'', '' Neostapfia'', '' Odontostomum'', '' Ornithostaphylos'', '' Pickeringia'', '' Romneya'') are endemic or near-endemic as well. ''

Arctostaphylos ''Arctostaphylos'' (; from "bear" and "bunch of grapes") is a genus of plants comprising the manzanitas () and bearberries. They are shrubs or small trees. There are about 60 species, of ''Arctostaphylos'', ranging from ground-hugging a ...

'', Brodiaeinae, ''

Calochortus ''Calochortus'' is a genus of flowering plants in the lily family. The group includes herbaceous, perennial and bulbous species, all native to North America (primarily the Western United States). The genus ''Calochortus'' includes mariposas ...

'', '' Caulanthus'', ''

Streptanthus ''Streptanthus'' is a genus of plants within the family Brassicaceae. There are about 35 known species within the genus ''Streptanthus'', distributed mostly throughout western North America. The common names for this genus are twistflower and je ...

'', ''

Ceanothus ''Ceanothus'' is a genus of about 50–60 species of nitrogen-fixing shrubs and small trees in the buckthorn family (Rhamnaceae). Common names for members of this genus are buckbrush, California lilac, soap bush, or just ceanothus. ''"Ceanothus"' ...

'', '' Cryptantha'', ''

Downingia ''Downingia'' is a genus of 13 annual plants native to western North America and Chile. Commonly known as calico flowers, they are notable for forming mass displays of small but colorful blooms around vernal pool Vernal pools, also called ver ...

'', '' Dudleya'', Eritrichieae, Eriogonoideae, Gileae, Hydrophyllaceae, Limnanthaceae, ''

Lotus Lotus may refer to: Plants *Lotus (plant), various botanical taxa commonly known as lotus, particularly: ** ''Lotus'' (genus), a genus of terrestrial plants in the family Fabaceae **Lotus flower, a symbolically important aquatic Asian plant also ...

'', Madiinae, '' Mimulus'', Onagreae, Epilobieae, Orcuttieae, Eschscholzioideae, Platystemonoideae, ''

'' and ''

Cupressus ''Cupressus'' is one of several genera of evergreen conifers within the family Cupressaceae that have the common name cypress; for the others, see cypress. It is considered a polyphyletic group. Based on genetic and morphological analysis, the ge ...

'' have a principal center of diversity within the province. The flora of the Californian Province is partially shared with the spatially distant Chile-Patagonian Region of the Antarctic Kingdom and to a lesser extent

Mediterranean Region In biogeography, the Mediterranean Basin (; also known as the Mediterranean Region or sometimes Mediterranea) is the region of lands around the Mediterranean Sea that have mostly a Mediterranean climate, with mild to cool, rainy winters and ...

of the Holarctic Kingdom. The vegetation of the Californian Province is varied. Wetter northern parts of the Californian Province (

Northern California Northern California (colloquially known as NorCal) is a geographic and cultural region that generally comprises the northern portion of the U.S. state of California. Spanning the state's northernmost 48 counties, its main population centers incl ...

and

Oregon Oregon () is a state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington, while the Snake River delineates much of its eastern boundary with Idah ...

) as defined by

Peter Raven Peter Hamilton Raven (born June 13, 1936) is an American botanist and environmentalist, notable as the longtime director, now President Emeritus, of the Missouri Botanical Garden. Early life On June 13, 1936, Raven was born in Shanghai, China ...

and D.I. Axelrod, as well as by

Conservation International Conservation International (CI) is an American nonprofit environmental organization headquartered in Crystal City, Arlington, Virginia. CI's work focuses on science, policy and partnership with businesses, governments and communities. The or ...

, fall under the Rocky Mountain Region in Takhtajan and Thorne's system and don't make parts of the Madrean Region.

Sonoran Province

The Sonoran Province comprises arid areas in the southwestern U.S. and northwestern Mexico from

and

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

and

Tamaulipas Tamaulipas (), officially the Free and Sovereign State of Tamaulipas ( es, Estado Libre y Soberano de Tamaulipas), is a state in the northeast region of Mexico; one of the 31 states which, along with Mexico City, comprise the 32 Federal Entiti ...

, including the Mojave (characterized by '' Yucca brevifolia'', Joshua Tree),

Sonora Sonora (), officially Estado Libre y Soberano de Sonora ( en, Free and Sovereign State of Sonora), is one of the 31 states which, along with Mexico City, comprise the Federal Entities of Mexico. The state is divided into 72 municipalities; the ...

and

Chihuahua Chihuahua may refer to: Places *Chihuahua (state), a Mexican state **Chihuahua (dog), a breed of dog named after the state **Chihuahua cheese, a type of cheese originating in the state **Chihuahua City, the capital city of the state **Chihuahua Mun ...

Deserts. The vegetation is dominated by ''

Yucca ''Yucca'' is a genus of perennial shrubs and trees in the family Asparagaceae, subfamily Agavoideae. Its 40–50 species are notable for their rosettes of evergreen, tough, sword-shaped leaves and large terminal panicles of white or whitish ...

'', Cactaceae species (''

Opuntia ''Opuntia'', commonly called prickly pear or pear cactus, is a genus of flowering plants in the cactus family Cactaceae. Prickly pears are also known as ''tuna'' (fruit), ''sabra'', '' nopal'' (paddle, plural ''nopales'') from the Nahuatl word ...

'' spp. and other), as well as by ''

Larrea tridentata ''Larrea tridentata'', called creosote bush and greasewood as a plant, chaparral as a medicinal herb, and ''gobernadora'' ( Spanish for "governess") in Mexico, due to its ability to secure more water by inhibiting the growth of nearby plants. In ...

'' (Creosote bush).

Mexican Highlands Province

The Mexican Highlands Province comprises areas in the

Mexican Plateau The Central Mexican Plateau, also known as the Mexican Altiplano ( es, Altiplanicie Mexicana), is a large arid-to-semiarid plateau that occupies much of northern and central Mexico. Averaging above sea level, it extends from the United States b ...

region, including Madrean pine-oak woodlands.

Bibliography

*Thorne, Robert F
Phytogeography of North America North of Mexico
''

Flora of North America The ''Flora of North America North of Mexico'' (usually referred to as ''FNA'') is a multivolume work describing the native plants and naturalized plants of North America North America is a continent in the Northern Hemisphere and a ...

'', Vol. 1, Ch. 6. {{Flora of the United States by political division Floristic regions * Natural history of Mexico Plant communities of the Western United States Plant communities of California Mexican Plateau * Natural history of the Colorado Desert Natural history of the Mojave Desert Holarctic

Floristic provinces

Great Basin Province

Californian Province

Sonoran Province

Mexican Highlands Province

See also

Bibliography