Australian Region

Australian Region

 

one of the faunal and floral geographic regions of the earth’s land.

The Australian zoogeographic region includes Australia and a number of islands: Tasmania, New Guinea, the Solomons, the Bismarck Archipelago, part of the Lesser Sun-das, New Zealand, Melanesia, Micronesia, Polynesia, and the Hawaiian islands. The Australian floristic region, however, includes only Australia and Tasmania, since animals and plants have different capacities for migration. The animal and plant worlds of the Australian region are distinguished by remarkable peculiarities and great antiquity, because Australia was linked to adjacent parts of Asia in the Mesozoic era, when lower forms of mammals—monotremes and marsupials—migrated to it. Australia’s subsequent isolation enabled the animals and plants that inhabited it to continue to develop along their own independent path.

Flora. The rich and distinctive flora of the Australian region includes about 12,000 varieties of plants, about 9,100 of which are endemic—that is, proper only to the Australian region. Almost the entire eucalyptus family, phylloid acacia, beefwoods, so-called grass trees, and other plants of the region are encountered nowhere outside its limits. Ancient genera characteristic of tropical and temperate climates—for example, the phylloid acacia, eucalyptus, beefwood, Xanthorrhoea, Tristania—constitute the core of Australia’s endemic flora. However, breaks in the areals of many plants (Jacksonia, banksia, and others) are observed in the central part of Australia; this can be explained by the ancient, lengthy separation of the western and eastern portions of Australia by the sea. In a number of cases, community with the flora of the Antarctic and Cape regions is observed (beech, cypress, magnolia, araucaria, woody ferns, and Proteaceae) as the consequence of an Antarctic land mass, including Australia and other continents and islands, during the Mesozoic era. On the slopes of high mountains and on the plateau of the Great Dividing Range, there are places where the timberline does not reach the peaks themselves. Such northern mountain plants as ranunculos, gentian, veronica, viola, and Gnaphalium, are encountered in subalpine and alpine meadows.

The flora of the Australian region is not uniform. The saline deserts of the central regions are covered with halophytic vegetation (glasswort, summer cypress, and goosefoot), and the sandy deserts are covered with sturdy, thorny grasses (triodia and spinifex). Bordering this region on the east and west are vast territories with thickets of stiff-leaved shrubs (scrub). In the northwest and east, they gradually give way to vast savannas with low phylloid acacias and eucalyptus, which are replaced further on by savanna forests. Moving closer to the sea in the southwest and east of the continent, one encounters evergreen subtropical forests; on the shores of the Coral Sea there are also humid tropical forests, similar in structure and origin to the neighboring ones of Malaya. Subtropical and subantarc-tic forests of the Australian region are distinguished by giant eucalyptus (over 100 m tall and up to 12 m in diameter), woody ferns, fern palms, and so forth. Steppe sections and scrub are encountered on the island of Tasmania. Genuine Antarctic forests of Chilean beech and Antarctic conifers—Japanese yew and phylloclade—and others grow in the mountains. The Australian region has almost no endemic cultivated plants with succulent fruits. It is the native region of the drought-resistant trees and shrubs that have spread in cultivation throughout the world—particularly eucalyptus and acacia.

The Australian region has the following subregions: (1) Southwest, (2) Eremeya, (3) Northeast, (4) Southeast, and (5) Tasmania.

V. S. GOVORUKHIN

The Australian zoogeographic region is one of the six zoogeographic land regions of the world. It was first established by the English scholar P. L. Sclater and substantiated more fully by the English naturalist A. R. Wallace; it has been universally recognized in subsequent land-division systems. The fauna is not very rich—a consequence of Australia’s ancient separation, along with New Guinea, from neighboring continents. The region is characterized by an abundance of endemic genera and families and a small number of higher, or placental, mammals; excluding animals which had been brought by man and which later ran wild—for instance, dogs, pigs, rabbits, and foxes. Only bats, which are able to fly over broad straits, and some genera of true mice, whose ancestors could have been carried on tree trunks by the current, are typical of the region. Marsupials developed to an exceptional degree in the Australian region—there are about 50 genera (162 species); outside the Australian region there are only two families of marsupials—marsupial rats and caenolestids—which are found in South America.

Diverse forms of marsupials correspond to different biological types of higher mammals: carnivores—the marsupial wolf and marsupial marten; insectivores—the marsupial anteater and marsupial mole; rodents of the steppe marmot type—wombats; rodents of the squirrel and flying squirrel type—the marsupial squirrel and climbing marsupials (the cuscus and koala); and ungulates—the great kangaroo. Today, egg-laying mammals (monotremes) are indigenous only to the Australian region, and are represented by the platypus and echidna.

Of the 670 species of birds inhabiting the Australian region, about 450 are endemic: the order of Casuarius (with the families of cassowaries and emus), families of bowerbirds and birds of paradise (more than 100 species), honeyeaters (about 200 species), lyrebirds, cockatoos, hawk owls, budgerigars, scrub fowl, black swans, kingfishers, and doves (for example, the crested doves). The frilled lizard and mountain devil are representative of reptiles, and the lungfish (Ceratodontidae), of the region’s fish. The Bupres-tidae and Cerambycidae beetle families and the Cossidae and Hepialidae butterfly families are abundant. Butterflies of the Papilionidae family are indigenous to New Guinea and neighboring islands.

The subregions of the Australian zoogeographic region are the (1) Papuan (New Guinea)—New Guinea and the western islands within the Australian region, the Solomon Islands, and northern Australia; (2) Australian (New Holland)—most of Australia and Tasmania; (3) New Zealand—New Zealand and the islands of Auckland, Mac-quarie, and Chatham; (4) Polynesian—the islands of Polynesia, Micronesia, and Melanesia; and (5) Hawaiian—the Hawaiian islands.

V. G. GEPTNER

REFERENCES

Geptner, V. G. Obshchaia zoogeografiia. Moscow-Leningrad, 1936.
Puzanov, I. I. Zoogeografiia: Kharakternye zhivotnye Avstraliiskoi oblasti. Moscow, 1938.
Vul’f, E. V. Istoricheskaia geografiia rastenii, [2nd ed.]. Moscow-Leningrad, 1944.
Bobrinskii, N. A., L. A. Zenkevich, and Ia. A. Birshtein. Geografiia zhivotnykh. Moscow, 1946.
Alekhin, V. V., L. V. Kudriashov, and V. S. Govorukhin. Geografiia rastenii s osnovami botaniki, 2nd ed. Moscow, 1961.
Schmithósen, J. Obshchaia geografiia rastitel’nosti. Moscow, 1966. (Translated from German.)
Burbidge, N. T. “The Phytogeography of the Australian Region.” Australian Journal of Botany, 1960, vol. 8, no. 2.
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