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 r ...

within the Holarctic Kingdom in

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

, as delineated by

Armen Takhtajan Armen Leonovich Takhtajan or Takhtajian ( hy, Արմեն Լևոնի Թախտաջյան; russian: Армен Леонович Тахтаджян; surname also transliterated Takhtadjan, Takhtadzhi︠a︡n or Takhtadzhian, pronounced takh-tuh-JA ...

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 Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

and northwestern

Mexico Mexico (Spanish language, Spanish: México), officially the United Mexican States, is a List of sovereign states, country in the southern portion of North America. It is borders of Mexico, bordered to the north by the United States; to the so ...

and is bordered by the

Rocky Mountain Region The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...

and

North American Atlantic Region North American Atlantic Region is a floristic region within the Holarctic Kingdom identified by Armen Takhtajan and Robert F. Thorne, spanning from the Atlantic and Gulf coasts to the Great Plains and comprising a major part of the United States ...

of the Holarctic Kingdom in the north and in the east,

Caribbean Region The Caribbean region of Colombia or Caribbean coast region is in the north of Colombia and is mainly composed of 8 departments located contiguous to the Caribbean.Neotropical Kingdom The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropical terrestrial ecoregions of the Americas and the entire South American temperate zone. Definition In bioge ...

in the south. The Madrean Region is characterized by a very distinct

flora Flora is all the plant life present in a particular region or time, generally the naturally occurring ( indigenous) native plants. Sometimes bacteria and fungi are also referred to as flora, as in the terms '' gut flora'' or '' skin flora''. ...

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 else ...

families (

Fouquieriaceae ''Fouquieria'' is a genus of 11 species of desert plants, the sole genus in the family Fouquieriaceae. The genus includes the ocotillo ('' F. splendens'') and the Boojum tree or cirio ('' F. columnaris''). They have semisucculent stems with thin ...

, Simmondsiaceae, and

Setchellanthaceae ''Setchellanthus caeruleus'' is a species of pungent shrub with large blue flowers. It is placed alone in the genus ''Setchellanthus'', which is in turn, is placed alone in the family Setchellanthaceae. It is endemic to Mexico. The genus and the ...

). Crossosomataceae, Garryaceae, Lennoaceae,

Limnanthaceae The Limnanthaceae are a small family of annual herbs occurring throughout temperate North America. There are eight species and nineteen taxa currently recognized. Members of this family are prominent in vernal pool communities of California. Some ...

and

Stegnospermataceae ''Stegnosperma'' is a genus of flowering plants, consisting of three species of woody plants, native to the Caribbean, Central America, and the Sonoran Desert. These are shrubs or lianas, with anomalous secondary thickening in mature stems, by su ...

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 diver ...

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 nomenclat ...

and probably more than half of the

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 ...

of the region are

to it according to Takhtajan.

Floristic provinces

The region is subdivided into four floristic provinces: * Great Basin Province *

Californian Province The California Floristic Province (CFP) is a floristic province with a Mediterranean-type climate located on the Pacific Coast of North America with a distinctive flora similar to other regions with a winter rainfall and summer drought climate ...

*Sonoran Province * Mexican Highlands Province

Great Basin Province

The Great Basin Floristic Province includes most of the

Great Basin The Great Basin is the largest area of contiguous endorheic watersheds, those with no outlets, in North America. It spans nearly all of Nevada, much of Utah, and portions of California, Idaho, Oregon, Wyoming, and Baja California. It is noted fo ...

, 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 o ...

, the

Snake River Plain The 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. It stre ...

, and Arizona north of the Mogollon Rim. 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 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 ...

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 tempe ...

'', ''

Eriogonum ''Eriogonum'' is a genus of flowering plants in the family Polygonaceae. The genus is found in North America and is known as wild buckwheat. This is a highly species-rich genus, and indications are that active speciation is continuing. It incl ...

'', ''

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 and t ...

'', ''

Cryptantha ''Cryptantha'' is a genus of flowering plants in the borage family, Boraginaceae. They are known commonly as cat's eyes and popcorn flowers (the latter name is also used to refer to the closely related genus ''Plagiobothrys'',Hasenstab-Lehman, ...

'', ''

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 y ...

'', ''

Erigeron ''Erigeron'' () is a large genus of plants in the family Asteraceae. It is closely related to the genus ''Aster'' and the true daisies in the genus ''Bellis''. The genus has a cosmopolitan distribution in dry, mountainous areas and grassland, wi ...

'', ''

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 recorded ...

'', ''

Castilleja ''Castilleja'', commonly known as paintbrush, Indian paintbrush, or prairie-fire, is a genus of about 200 species of annual and perennial herbaceous plants native to the west of the Americas from Alaska south to the Andes, northern Asia, and on ...

'', 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 Ameri ...

''. The vegetation in the central

Great Basin shrub steppe The Great Basin Desert is part of the Great Basin between the Sierra Nevada and the Wasatch Range. The desert is a geographical region that largely overlaps the Great Basin shrub steppe defined by the World Wildlife Fund, and the Central Basin a ...

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 i ...

genera. The

Great Basin montane forests The Great Basin montane forests is an ecoregion of the Temperate coniferous forests biome, as designated by the World Wildlife Fund (WWF). Geography The Great Basin montane forests ecoregion is located in the Great Basin region of Nevada, easte ...

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, an ...

(''Pinus longaeva'') trees.

Californian Province

The

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 m ...

from the seashore to the foothills of the

Cascade Range The Cascade Range or Cascades is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, ...

, 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 primar ...

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 ''Adenostoma'' is a genus of shrubs in the Rose family (Rosaceae) containing only two species, chamise (''Adenostoma fasciculatum'') and redshanks (''Adenostoma sparsifolium''). Both are native to the Californias. Description Characteristic ...

'', ''

Bergerocactus ''Bergerocactus emoryi'' is a species of cactus, known commonly as the golden-spined cereus, golden snake cactus, velvet cactus or golden club cactus. It is a relatively small cactus, but it can form dense thickets or colonies, with the dense ye ...

'', '' Carpenteria'', '' Cneoridium'', ''

Dendromecon ''Dendromecon'', the tree poppy, is a genus of one or two species of shrubs to small trees, native to California and northern Baja California. The leaves are evergreen, alternate, lanceolate to ovate, 3–10 cm long. The flowers are yellow, ...

'', '' Fremontodendron'', ''

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 particular ...

'', ''

Lyonothamnus ''Lyonothamnus'' is a monotypic genus of trees in the rose family containing the single living species ''Lyonothamnus floribundus'', which is known by the common name Catalina ironwood, and the subspecies ''L. f.'' ssp. ''aspleniifolius'' and '' ...

'', ''

Neostapfia ''Neostapfia'' is a genus of endemic Californian bunchgrasses, in the subfamily Chloridoideae of the grass family, Poaceae. The only known species is ''Neostapfia colusana'', with the common name Colusa grass. Distribution ''Neostapfia colus ...

'', ''

Odontostomum ''Odontostomum'' is a monotypic genus of flowering plants containing the single species ''Odontostomum hartwegii'', which is known by the common name Hartweg's doll's-lily. In the APG III classification system, it is placed in the family Tecoph ...

'', '' Ornithostaphylos'', ''

Pickeringia ''Pickeringia'' is a monotypic genus of flowering plants in the legume family, Fabaceae. It was recently assigned to the unranked, monophyletic ''Cladrastis'' clade. It was named after the naturalist Charles Pickering. Its only species is ''Pic ...

'', ''

Romneya ''Romneya'' () is a genus of flowering plants belonging to the poppy family (Papaveraceae). There are two species in genus ''Romneya'', which was named for Irish astronomer John Thomas Romney Robinson. They are known commonly as Matilija poppies ...

'') 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 arc ...

'', 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 mariposa ...

'', '' Caulanthus'', '' Streptanthus'', ''

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. ''"Ceanothu ...

'', ''

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 verna ...

'', ''

Dudleya ''Dudleya'', commonly known as liveforevers ( Spanish: ''siemprevivas'') is a genus of succulent plants in the stonecrop family, Crassulaceae, consisting of about 68 taxa in southwestern North America and Guadalupe Island. The species come in mu ...

'', Eritrichieae, Eriogonoideae, Gileae, Hydrophyllaceae,

, '' Lotus'',

Madiinae Madieae is a tribe of flowering plants in the family Asteraceae. It is sometimes considered a subtribe of Heliantheae. Notable species include the tarweeds of the Western United States as well as the silverswords of Hawaii. Subtribes and g ...

, ''

Mimulus Mimulus is a plant genus in the family Phrymaceae, which was traditionally placed in family Scrophulariaceae. The genus now contains only seven species, two native to eastern North America and the other five native to Asia, Australia, Africa, ...

'', 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 ...

'' 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 wa ...

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 U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...

) 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 org ...

, fall under the

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: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by ...

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 ''Yucca brevifolia'' is a plant species belonging to the genus ''Yucca''. It is tree-like in habit, which is reflected in its common names: Joshua tree, yucca palm, tree yucca, and palm tree yucca. This monocotyledonous tree is native to the ar ...

'', 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 Mu ...

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 whitis ...

'',

Cactaceae A cactus (, or less commonly, cactus) is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1750 known species of the order Caryophyllales. The word ''cactus'' derives, through Latin, from the Ancient Gre ...

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'' (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 The Madrean Region (named after the Sierra Madre Occidental) is a floristic region 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 Unite ...

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, including the United States, Canada, St. Pierre and Miquelon, and Greenlan ...

'', 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