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 anteater...