Biogeographical RegionsRichard Huggett, University of Manchester, Manchester, UK
Species are not uniformly distributed over the land surface. Fauna and flora display regional
differences. The largest regions of animals and plants are biogeographical regions, each
bearing a distinctive fauna and flora. Some families and even some orders of animals are
endemic to particular biogeographical regions. Other families are shared by two or more
regions. A few families are cosmopolitan, being found in all biogeographical regions.
P. L. Sclater, A. R. Wallace and theFoundational Units of Biogeography
Dierent places harbour dierent kinds of animals andplants. The fauna of Africa is unlike the fauna of NorthAmerica; the ora of Japan is unlike the ora of SouthAfrica. These regional dierences in the distribution ofspecies became increasingly manifest as the world wasexplored. George Leclerc, Compte de Buon (17071788)studied the then known tropical mammals from the OldWorld (Africa) and the New World (Central and SouthAmerica). He found that they had not a single species incommon. Later comparisons of African and SouthAmerican plants, insects and reptiles evinced the samepattern.By the nineteenth century, it was clear that the land
surface couldbedivided intobiogeographical regions, eachofwhich carries a distinct set of animals and adistinct set ofplants. Augustin-Pyramus de Candolle considered plantsand identied areas of endemism, that is botanical regions,each possessing a certain number of plants peculiar tothem. He listed 20 such botanical regions or areas ofendemism in 1820, and by 1838 had added another score,bringing the total to 40. In 1826, James Cowles Prichard, azoologist, distinguished seven regions of mammals: theArctic region, the temperate zone, the equatorial regions,the Indian isles, the Papuan region, the Australian region,and the extremities of America and Africa. WilliamSwainson modied this scheme in 1835, by taking accountof the ve recorded varieties of humans, to give veregions: the European (or Caucasian) region, the Asiatic(orMongolian) region, theAmerican region, theEthiopian(or African) region, and the Australian (or Malay) region.The early ideas of Prichard and Swainson on animal
distributions were eclipsed by the seminal work of anEnglish ornithologist, Philip Lutley Sclater, and theeminent English biogeographer and naturalist, AlfredRussel Wallace. Using bird distributions, Sclater (1858)recognized two basic divisions (or creations, as he termedthem) the Old World (Creatio Paleogeana) and the NewWorld (Creatio Neogeana) and six regions. The OldWorld he divided into Europe and northern Asia, Africasouth of the Sahara, India and southern Asia, and
Australia and New Guinea. The New World he dividedinto North America and South America. Sclaters schemaprompted a urry of papers by English-speaking zoolo-gists, including Thomas Henry Huxley and Joel AsaphAllen, each of whom promulgated his own favouredgeographical classication. In his The Geographical Dis-tribution of Animals (1876), Wallace reviewed the compet-ing systems, arguing persuasively in favour of adoptingSclaters six regions, or realms as Wallace dubbed them.Sclaters system and Wallaces minor amendments to itprovided a nomenclature that survives today (Figure 1).Later suggestions were minor variations on the SclaterWallace theme. Sclater andWallace identied six regions Nearctic, Neotropical, Palaearctic, Ethiopian, Orientaland Australian. Together, the Nearctic and Palaearcticregions form Neogaea (the New World), while otherregions form Palaeogaea (the Old World). Wallacescontribution was to identify subregions, four per region,which correspond largely to de Candolles botanicalregions. Indeed, the nineteenth-century classication of
. P. L. Sclater, A. R. Wallace and the Foundational Unitsof Biogeography
. Floral Regions
. Comparisons and Contrasts between Taxa
. Transitional Zones and Filters
. The Applied Use of Biogeographical Regions: TheirPlace in Conservation
Nearctic Neotropical Palaearctic
Ethiopian Oriental Australian
Figure 1 The six faunal regions delimited by Sclater and Wallace.
1ENCYCLOPEDIA OF LIFE SCIENCES 2002, John Wiley & Sons, Ltd. www.els.net
biogeographical regions was essentially an attempt togroup areas of endemism into a hierarchical classicationaccording to the strengths of their relationships.It is surprising and noteworthy that the distributions of
species with good dispersal abilities, including plants,insects and birds, tend to fall within traditional zoogeo-graphical regional connes. The avifaunas of NorthAmerica and Europe contain several families and manygenera that are not shared by the two regions, even thoughdispersal across the North Atlantic and Pacic Oceans byaccidental visitors is noted every year. Even long-distancemigrant bird taxa tend to be conned either to the easternhemisphere or to the western hemisphere, where theymigrate between high and low latitudes, and appear ill-disposed to disperse eastwest between continents.
Of the six faunal regions delineated bySclater andWallace,the Palaearctic is the largest. It includes Europe, NorthAfrica, theNear East andmuch ofAsia (but not the Indiansubcontinent or Southeast Asia). Its mammal fauna isquite rich, with some 40 families. Only twoof these familiesare endemic to the Palaearctic region the blind mole rats(Spalacidae) and the Seleviniidae, represented by onespecies, the dzhalman, which is a small insectivorousrodent.The Nearctic region encompasses nearly all the New
World north of tropical Mexico. Its fauna is diverse andincludes families with a largely tropical distribution, suchas the sac-winged or sheath-tailed bats (Emballonuridae),vampire bats (Desmodontidae), and javelinas or peccaries(Tayassuidae), and largely boreal families, such as thejumping mice (Zapodidae), beavers (Castoridae), andbears (Ursidae). Only two Nearctic families are endemicto the region: the Aplodontidae, which contains onespecies, the mountain beaver or sewellel, and the Antilo-capridae, which also contains one species, the pronghornantelope. Two other families are almost endemic: thepocket gophers (Geomyidae) live in North America,Central America and northern Colombia; and the kangar-oo rats and pocket mice (Heteromyidae) live in NorthAmerica, Mexico, Central America and northwesternSouth America.The Neotropical region covers all the NewWorld south
of tropical Mexico. It boasts some 27 endemic families ofmammals: the solenodons (Solenodontidae), the recentlyextinct West Indian shrews (Nesophontidae), New Worldmonkeys (Cebidae), marmosets (Callithricidae), caeono-lestids or marsupial mice (Caenolestidae), the monito delmonte or monkey of the mountains (Microbiotheriidae),anteaters (Myrmecophagidae), sloths (Bradypodidae),and 12 caviomorph rodent families. The rodent familiesare the degus, coruros, and rock rats (Octodontidae), tuco-
tucos (Ctenomyidae), spiny rats (Echimyidae), rat chinch-illas (Abrocomidae), hutias and coypus (Capromyidae),chinchillas and viscachas (Chinchillidae), agouties (Dasy-proctidae), pacas (Cuniculidae), the pacarana (Dinomyi-dae), guinea-pigs and their relatives (Caviidae), capybaras(Hydrochoeridae), and the recently extinct quemi and itsallies (Heptaxodontidae). The other seven endemic Neo-tropical families are bats bulldog bats (Noctilionidae),NewWorld leaf-nosed bats (Phyllostomidae), moustachedbats, ghost-faced bats and naked-backed bats (Mormoo-pidae), vampire bats (Desmondontidae, which someauthorities include with the Phyllostomidae), funnel-earedbats (Natalidae), smoky or thumbless bats (Furipteridae)and disc-winged bats (Thyropteridae).The Ethiopian region encompasses Madagascar, Africa
south of a somewhat indeterminate line running across theSahara, and a southern strip of the Arabian peninsula. Ithas about 15 endemic families, almost as many as theNeotropical region. The families are the giraes (Gira-dae), hippopotamuses (Hippopotamidae, though thoseliving on the Lower Nile are technically in the Palaearcticregion), the aardvark (Orycteropodidae), tenrecs (Tenre-cidae), the Old World sucker-footed bats (Myzopodidae),lemurs (Lemuridae), woolly lemurs (Indriidae), aye-ayes(Daubentoniidae), two families of shrew, and ve familiesof rodent. The shrew families are the golden moles(Chrysochloridae) and otter shrews (Potamogalidae).The rodent families are the scaly-tailed squirrels (Anom-aluridae), the spring hare or Cape jumping hare (Pedeti-dae), cane rats (Thryonomydiae), the rock rat or dassie rat(Petromyidae), andAfricanmole rats (Bathyergidae). Twoother families the elephant shrews (Macroscelididae) andgundis (Ctenodactylidae) are conned to Africa butrange into the north of the continent, which is part of thePalaearctic region.The Oriental region covers India, Indo-China, southern
China, Malaysia, the Philippines, and Indonesian islandsas far east as Wallaces line. It has just four endemicfamilies: spiny dormice (Platacanthomyidae), tree shrews(Tupaiidae), tarsiers (Tarsiidae), and ying lemurs orcolugos (Cynocephalidae). It also has one endemic batfamily, the Craseonycteridae, represented by a singlespecies known as Kittis hog-nosed bat or bumblebeebat, which was discovered in Thailand in 1973.The Australian region includes mainland Australia,
Tasmania, New Guinea, Sulawesi, and many smallIndonesian islands. It possesses some 19 endemic familiesof mammals: the echidnas or spiny anteaters (Tachyglos-sidae), the platypus (Ornithorhynchidae),marsupial miceand cats (Dasyuridae), the Tasmanian wolf (Thylacini-dae), the numbat or banded anteater (Myrmecobiidae), themarsupial mole (Notoryctidae), bandicoots and bilbies(Peramelidae), burrowing bandicoots (Thylacomyidae),spiny bandicoot and mouse bandicoot (Peroryctidae),striped possum, Leadbeaters possum and wrist-wingedgliders (Petauridae), feathertail gliders (Acrobatidae),
pigmy possums (Burramyidae), brush-tailed possums,cuscuses, scaly-tailed possums (Phalangeridae), ringtailpossums and great glider (Pseudocheiridae), kangaroosand wallabies (Macropodidae), rat kangaroos, potoroos,and bettongs (Potoroidae), koalas (Phascolarctidae),wombats (Vombatidae), and the noolbender or honeypossum (Tarsipedidae).
In The Geography of the Flowering Plants (1974), Britishbotanist Ronald Good summarized the distribution ofliving angiosperms by adapting a scheme devised by AdolfEngler during the 1870s. Good delineated six major oralregions, though he styled them kingdoms: the Borealregion, the Palaeotropical region, the Neotropical region,theAustralian region, SouthAfrican (Cape) region and theAntarctic oral region. Each of these comprises a numberof subregions (Good called them regions), of which thereare 37 in total (Figure 2). The Boreal oral region spansNorth America and Asia, which share many families,including the birches, alders, hazels and hornbeams(Betulaceae), mustard (Cruciferae), primrose (Primula-ceae) and buttercup (Ranunculaceae). Six subregions arerecognized: the Arctic and Subarctic, East Asia, Westernand Central Asia, the Mediterranean, Euro-Siberia andNorth America. The Palaeotropical region covers most ofAfrica, the Arabian peninsula, India, southeast Asia, andparts of the western and central Pacic. The subregions arenot rmly agreed, butMalesia, Indo-Africa, and Polynesiaare commonly recognized. The Malesian subregion isexceptionally rich in forms, with about 400 endemicgenera. Madagascar, which is part of the Indo-Africansubregion but sometimes taken as a separate region, has 12endemic families and 350 endemic genera. TheNeotropicalregion coversmost of SouthAmerica, save the southern tipand a southwestern strip, Central America, Mexico(excepting the dry northern and central sections), and theWest Indies and southern extremity of Florida. It isgloriously rich oristically, housing 47 endemic familiesand nearly 3000 endemic genera. The Cape region ofSouth Africa is, for its small size, rich in plants, with11 endemic families and 500 endemic genera. TheAustralian region is highly distinct with 19 endemicfamilies, 500 endemic genera, and over 6000 owering-plant species. The Antarctic region has a curiousgeography and includes a coastal strip of Chile and thesouthern tip of South America, the Antarctic andsubantarctic islands, and New Zealand. The subantarcticsubregion (southern Chile, Patagonia and New Zealand)carries a distinctive ora involving some 50 genera, ofwhich the southern beech (Nothofagus) is a characteristicelement.
Comparisons and Contrasts betweenTaxa
The worlds regional faunas are linked with each other incomplex ways, as are the worlds regional oras. Connec-tions at the species level are weak, except between thePalaearctic and Nearctic regions, but some regions sharegenera and families. Each biogeographical region pos-sesses two groups of families: those that are endemic orpeculiar to the region, and those that are shared with otherregions. Although no agreed system of naming shared taxa(species, genera, families, or whatever) exists, a useful
Arctic and Sub-arcticEuroSiberiana. Europeb. AsiaSinoJapaneseW. and C. AsiaticMediterraneanMacaronesianAtlantic North Americana. Northernb. SouthernPacific North American
AfricanIndian DesertSudanese Park SteppeN. E. African HighlandW. African RainforestE. African SteppeSouth AfricanMadagascarAscension and St. HelenaIndianContinental S. E. AsiaticMalaysianHawaiianNew CaledoniaMelanesia and MicronesiaPolynesia
CaribbeanVenezuela and GuianaAmazonSouth BrazilianAndreanPampasJuan Fernandez
N. and E. AustralianS. W. AustralianC. Australian
South African region31 Cape
New ZealandPatagonianS. Temp.Oceanic Islands
Figure 2 The six floral regions and 37 subregions mapped by Good.
scheme suggests that taxa shared between two biogeogra-phical regions are characteristic, taxa shared betweenthree or four biogeographical regions are semi-cosmopo-litan, and taxa shared between ve or more biogeogra-phical regions are cosmopolitan. Links between regionsare suggested by amixing of some faunal or oral elements.A Malesian oral element is present in the tropicalrainforests of northeastern Queensland, Australia. Ant-arctic andPalaeotropical ora interdigitate in South Islandof New Zealand, Tasmania and the Australian Alps. Thestrong anity of the Ethiopian andOriental faunal regionsis reected in a number of shared families: bamboo rats(Rhizomyidae), elephants (Elephantidae), rhinoceroses(Rhinocerotidae), chevrotains (Tragulidae), lorises andpottos (Lorisidae), galagos or bushbabies (Galagonidae),apes (Pongidae), and pangolins or scaly anteaters (Man-idae).
A new look at mammal regions
The similarities and dierences of dierent biogeographi-cal regions are brought out clearly by applying modernmethods of numerical classication to mammal distribu-tions. By applying multidimensional scaling to data on thedistribution of 115 mammal families (wholly marinefamilies and the human family were omitted) in Wallaces24 subregions, Charles H. Smith delineated similar regionsto those in the SclaterWallace scheme, but signicantdierences emerged. In Smiths 1983 system, there are fourregions Holarctic, Latin American, Afro-Tethyan andIsland and 10 subregions (Figure 3). The Holarctic regioncomprises the Nearctic and the Palaearctic subregions; theLatin American region comprises the Neotropical andArgentine subregions; the Afro-Tethyan region comprisesthe Mediterranean, Ethiopian and Oriental subregions;and the Island region comprises the Australian, the West
Indian and Madagascan subregions. Each subregion is asunique as it can be compared with all other subregions.Several features of Smiths system are intriguing. First, itreveals a close similitude between the mammal families ofthe Ethiopian and Oriental regions. Second, it includes theMediterranean subregion within the Ethiopian region,thus excluding it from the Palaearctic region. Third, itpromotes Madagascar and the West Indies to distinctisland subregions, removing them from the Ethiopianregion and the Neotropical region, respectively.The regional richness and endemicity of mammal
families in Smiths regions and subregions are as follows:the Holarctic has 36 families, of which six (17%) areendemic; the Latin American region has 48 families, ofwhich 20 (42%) are endemic; the Afro-Tethyan region has65 families, of which 29 (45%) are endemic; and the Islandregion has 35 families, of which 15 (43%) are endemic. Ofthe 115mammal families used in the analysis, 43 (37%) areendemic to subregions. The lowest subregional endemicityoccurs in the Palaearctic subregion, with no endemicfamilies, and the highest in theNeotropical subregion,withnine endemic families. Smiths analysis also indicated thatthe Nearctic, Palaearctic, Mediterranean and Orientalsubregions have high anities with the faunas of othersubregions, whereas the Argentine and Australian sub-regions have low anities with the faunas of othersubregions. Furthermore, the eects of isolation orinaccessibility (or both) are reected in the nature of theNeotropical, Argentine, Ethiopian, Australian, WestIndian and Madagascan faunas.
Faunal and floral regions compared
The major oral regions and the major faunal regions areroughly congruent, but there are important dierencesbetween them. First, owing to the superior dispersal abilityof some plants compared with terrestrial mammals, theoral regions tend to be less sharply dened than do thefaunal regions. Second, although the boreal oral region isequivalent to the combined Palaearctic and Nearcticfaunal regions (the Holarctic region), the North Americanoral subregion diers from the Nearctic faunal region inthat it does not occupy all of Florida or Baja California.The Palaeotropical oral region is equivalent to thecombined Ethiopian andOriental faunal regions or a largepart of Smiths Afro-Tethyan region, excluding theMediterranean, which is oristically grouped with theBoreal region. The Australian oral region approximatelycorresponds with the Australian faunal region, though thedividing line with the Asian region lies between Australiaand New Guinea, rather than farther west as in the case ofanimals. Indeed, it is puzzling that the ora ofNewGuineais Palaeotropical while its fauna is Australian. TheNeotropical oral region broadlymatches theNeotropicalfaunal region, but the oral Neotropical region, unlike the
Holarctic LatinAmericanAfro-Tethyan Island
Figure 3 The four faunal regions and 10 subregions recognized by Smith.
faunalNeotropical region, takes in BajaCalifornia and thesouthern end of Florida. The Cape oral region, whichoccupies the southern tip of Africa, bears no equivalentfaunal region. The Antarctic oral region, which, like theCape oral region, possesses no faunal counterpart,includes southern South America and New Zealand, andsome of its members are found in Tasmania and south-eastern Australia.
Transitional Zones and Filters
The chief faunal and oral regions are separated from oneanother by various kinds of barriers determined mainly byclimate, mountains and water gaps. The Nearctic isseparated from the Palaearctic by two water gaps theBering Strait and the Norwegian Sea, both of whichexperience cold climates. A narrow land-link (the Isthmusof Panama), which replaced an earlier water gap, separatesthe Nearctic region from the Neotropical region, with aridconditions lying north of the land link in Mexico. TheSahara Desert divides the Palaearctic region from theEthiopian region. The Ethiopian region is insulated fromthe Oriental region by arid lands in southwest Asia and theArabian peninsula. The Himalayas and their eastwardextensions create a formidable barrier between theOrientalregion and the Palaearctic region. In the region sometimescalled Wallacea, a series of water gaps hinders movementbetween the Oriental region and the Australian region.The borders between biogeographical regions may be
crossed with varying levels of ease or diculty. Seldom dothe environmental conditions in the border areas allowunhampered access between regions. A fairly open borderonce existed between Alaska and Siberia when, during thePleistocene epoch, there was a dry-land connection acrosswhat is now the Bering Strait. Other borders tend to act aslters and prevent the passage of some species from onebiogeographical region to another. In many cases, theborder area is transitional as the fauna or ora of onebiogeographical region intermixes with the fauna or oraof an adjacent biogeographical region. Two cases willillustrate these points.
The famous zoogeographical transition zone betweenLydekkers line and Wallaces line is sometimes calledWallacea (Figure 4). It is a large area in which Oriental andthe Australian faunas grade into one another. The faunasof both these regions thin out across the transition zone.Wallaces line, which passes betweenBali andLombok andalong the Makassar Strait between Borneo and Sulawesi,marks the easternmost extension of a wholly Orientalfauna.A fewOriental species (shrews, civets, pigs, deer andmonkeys) have colonized Sulawesi and Bali, but they are
genetically distinct from their relatives in the Orientalregion.A very fewOriental species, all of whichmight havebeen introduced, occur on the islands as far east as Timor,but no Oriental species live beyond that point. Lydekkersline, which passes between the Australian mainland andTimor and between New Guinea and Seram and Halma-hera, follows the edge of Australias continental shelf (theSahul Shelf). It marks the westernmost limit of a whollyAustralian fauna. A few Australian species are found onsome small islands a little to the west, and as far west asSulawesi and Lombok. Webers line (Figure 4) runs west oftheMoluccas and east of Timor, and marks places with anequal mix of Oriental and Australian species. It is taken bysome authorities as the dividing line between the Orientaland Australian faunas. However, the search for a hard-and-fast dividing line in such a patently transitional regionseems pointless.
The Isthmus of Panama
South America is presently connected to North America,but for most of the last 65 million years or so it was anisland-continent. Once during that time, from about 40 to36 million years ago, a land connection with NorthAmerica, probably through a chain of islands, existed.Two groups of mammal primates and ancestors of thecaviomorph rodents took advantage of the connectionand invaded South America. Having arrived in SouthAmerica, both groups underwent an impressive adaptiveradiation to produce the great variety of rodents and NewWorld monkeys found in South America today. From 30million to 6 million years ago, South America remained acolossal island and mammals had no possibility ofinteraction with other faunal regions. Even as recently as
Huxleys modificationof Wallaces line
100E 120E 140E
Figure 4 Wallacea the transition zone between the Oriental andAustralian faunal regions.
6 million years ago, the Bolivar Trough connected theCaribbean Sea with the Pacic Ocean and deterred thepassage of animals.However, at that time,members of twofamilies of mammals the eld mice (Cricetidae) andracoons, cacomistles, coati-mundis, kinkajous and olingos(Procyonidae) rafted across the seaway on clumps of soiland vegetation. By 3million years ago, a land connection the Panamanian land bridge had developed that supplieda gateway for faunal interchangebetweenNorth andSouthAmerica. A ood of mammals simply walked into SouthAmerica. Members of many families were involved:Cervidae (deer), camels (Camelidae), peccaries (Tayassui-dae), tapirs (Tapiridae), horses (Equidae), mastodons(Gomphotheriidae), rabbits (Leporidae), squirrels (Sciur-idae), shrews (Soricidae), mice (Muridae), dogs (Canidae),bears (Ursidae), weasels (Mustelidae) and cats (Felidae).The passage was two-way and is known as the GreatAmerican Interchange.
The Applied Use of BiogeographicalRegions: Their Place in Conservation
Each biogeographical region contains a combinationof species, genera and families, many of which areendemic. Each has a distinctive character that, withoutconservation measures, stands to be greatly diminished oreven lost. Natural biogeographical regions are threatenedby human activities, and in particular by habitat destruc-tion and fragmentation and by the introduction of alienspecies.
Habitat destruction and fragmentation
The human species has transformed the globe to such anextent that only fragments, admittedly some large, oforiginal fauna and ora remain in most biogeographicalregions.Natural habitats are conserved inwildlife reserves,where eorts are made to preserve the indigenous faunasand oras. Threatened species and communities stand aneven better chance of survival if the wildlife reserves arelinked by corridors. By the mid-1980s, 13 western NorthAmerican wildlife parks had lost 43% of their historicallagomorph (rabbits, hares and pikas), carnivore andungulate species. But the KootenayBanJasperYohopark system, which embodied signicant connectionsbetween wildlife reserves, maintained all its originalmammal fauna.The old idea that species could be preserved in zoos is no
longer seen as a workable option. Zoos have their place inconservation, for example enabling the reintroduction ofnear-extinct species to the wild, but much conservationeort now goes into protecting species in the survivingfragments of natural habitats. There is also a growing
realization that entire communities need conserving, andnot only fashionable species like the tiger and orang-utan.
Humans are watering down the distinctiveness of biogeo-graphical regions by the introduction of alien species: theyare homogenizing the global fauna and ora. Take the caseof New Zealand. Fifty-four mammal species have beenintroduced to the island.Twenty camedirectly or indirectlyfrom Britain and Europe, 14 from Australia, 10 from theAmericas, six fromAsia, two fromPolynesia and two fromAfrica. The package contained domestic animals forfarming and household pets and feral animals for sportor fur production. Farmanimals included sheep, cattle andhorses. Domestic animals included cats and dogs. Sportinganimals included pheasant, deer, wallabies and rabbits.The Australian possum was introduced to start a furindustry. Wild boars and goats were liberated on NewZealand by Captain James Cook.Many other species wereintroduced European blackbirds, thrushes, sparrows,rooks, yellow hammers, chanches, budgerigars, hedge-hogs, hares, weasels, stoats, ferrets, rats and mice. Ofcourse, natural invasions of alien species do take place, butnot, it would seem, at the human-induced rates prevalentover the last couple of centuries.Introduced species commonly have an adverse eect
upon native species. The Indian mongoose (Herpestesauropunctatus), introduced to various islands worldwide inthe hope of controlling rats and other vertebrate pests, hasled to the extinction of several native bird and reptilepopulations. Cats and rats introduced to islands have alsotended to have an inimical eect on native wildlife. Theinadvertent introduction of the sac fungus, Cryphonectria(Endothia) parasitica, into the United States around 1900led within 50 years to the near elimination of the Americanchestnut (Castanea dentata) from the native easternhardwood forests.
Theworlds terrestrial animals and plants are grouped intofaunal and oral regions. Six faunal regions are recognizedtraditionally, though a modern scheme, constructed usinga numerical classication technique, identies four regionsand 10 subregions. Six oral regions and 37 oral regionsare commonly distinguished. The oral and faunal regionsbear broad agreement with one another but displayimportant dierences of detail. The natural faunas andoras of biogeographical regions are unique. They areunder a severe threat from habitat destruction, habitatfragmentation, and the introduction of new species byhumans. Their long-term survival depends upon local andregional conservation schemes.
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