The Australasian realm

The Australasian realm is a biogeographic realm that is coincident with, but not (by some definitions) the same as, the geographical region of Australasia. The realm includes Australia, the island of New Guinea (comprising Papua New Guinea and the Indonesian province of Papua), and the eastern part of the Indonesian archipelago, including the island of Sulawesi, the Moluccas (the Indonesian provinces of Maluku and North Maluku), and the islands of Lombok, Sumbawa, Sumba, Flores, and Timor, often known as the Lesser Sundas.

The Australasian realm also includes several Pacific island groups, including the Bismarck Archipelago, Vanuatu, the Solomon Islands, and New Caledonia. New Zealand and its surrounding islands are a distinctive sub-region of the Australasian realm. The rest of Indonesia is part of the Indomalayan realm.[1] In the classification scheme developed by Miklos Udvardy, New Guinea, New Caledonia, Solomon Islands and New Zealand are placed in the Oceanian realm.[2][3]

Geography

From an ecological perspective the Australasian realm is a distinct region, parts of which have a common geologic and evolutionary history. The entire area has experienced a long period of biological isolation from other regions, and thus harbors a great many unique plants and animals. In this context, Australasia is limited to Australia, New Guinea, New Zealand, New Caledonia, and neighbouring islands, including the Indonesian islands from Lombok and Sulawesi eastward.

The Wallace Line to the west divides areas in the Indomalayan realm of tropical Asia which are or have at times been directly connected to the Asian mainland from islands that have never been so connected. Borneo and Bali lie on the western, Asian side. A second biological dividing line is Lydekker's Line, which similarly separates islands isolated by surrounding deep water from those associated with the Sahul Shelf of the Australian continent. Islands between the two lines (e.g. Sulawesi, the Moluccas and Lombok through Timor) form the biogeographical area of Wallacea, a transition zone between the Indomalayan and Australasian realms populated entirely by aerial or oceanic dispersal (although defined here as part of the Australasian realm).

Geology

Australia, New Zealand and New Caledonia are all fragments of the ancient supercontinent Gondwana, the marks of which are still visible in the Christmas Island Seamount Province and other geophysical entities. These three land masses have been separated from other continents, and from one another, for tens millions of years. All of Australasia shares the Antarctic flora, although the northern, tropical islands also share many plants with Southeast Asia.

Australia, New Guinea, and Tasmania are separated from one another by shallow continental shelves, and were linked together when the sea level was lower during ice ages. They share a similar fauna which includes marsupial and monotreme mammals and ratite birds. Eucalypts are the predominant trees in much of Australia and New Guinea. New Zealand has no native land mammals, but also had ratite birds, including the kiwi and the moa. The Australasian realm includes some nearby island groups, like Wallacea, the Bismarck Archipelago, Solomon Islands, and Vanuatu, which were not formerly part of Gondwana, but which share many characteristic plants and animals with Australasia.

Ecology

Note that this zonation is based on flora; animals do not necessarily follow the same biogeographic boundaries. In the present case, many birds occur in both "Indomalayan" and "Australasian" regions, but not across the whole of either. On the other hand, there are few faunistic commonalities shared only by Australia and New Zealand, except some birds. Meanwhile, Australia, Melanesia and the Wallacea are united by a large share of similar animals, but few of these occur farther into the Pacific. On the other hand, much of the Polynesian fauna is related to that of Melanesia.

Ecoregions

Ecoregions of the Australasian realm, color-coded by biome. Dark green: tropical and subtropical moist broadleaf forests. Light brown: tropical and subtropical dry broadleaf forests. Yellow: tropical and subtropical grasslands, savannas, and shrublands. Green: temperate broadleaf and mixed forests. Light green: temperate grasslands, savannas, and shrublands. Light blue: flooded grasslands and savannas. Light purple: montane grasslands and shrublands. Brown: Mediterranean forests, woodlands, and scrub. Beige: deserts and xeric shrublands. Magenta: mangroves.
Australasian tropical and subtropical moist broadleaf forests ecoregions
Admiralty Islands lowland rain forests Papua New Guinea
Banda Sea Islands moist deciduous forests Indonesia
Biak–Numfoor rain forests Indonesia
Buru rain forests Indonesia
Central Range montane rain forests Indonesia, Papua New Guinea
Halmahera rain forests Indonesia
Huon Peninsula montane rain forests Papua New Guinea
Lord Howe Island subtropical forests Australia
Louisiade Archipelago rain forests Papua New Guinea
New Britain–New Ireland lowland rain forests Papua New Guinea
New Britain–New Ireland montane rain forests Papua New Guinea
New Caledonia rain forests New Caledonia
Norfolk Island subtropical forests Australia
Northern New Guinea lowland rain and freshwater swamp forests Indonesia, Papua New Guinea
Northern New Guinea montane rain forests Indonesia, Papua New Guinea
Queensland tropical rain forests Australia
Seram rain forests Indonesia
Solomon Islands rain forests Papua New Guinea, Solomon Islands
Southeastern Papuan rain forests Papua New Guinea
Southern New Guinea freshwater swamp forests Indonesia, Papua New Guinea
Southern New Guinea lowland rain forests Indonesia, Papua New Guinea
Sulawesi lowland rain forests Indonesia
Sulawesi montane rain forests Indonesia
Trobriand Islands rain forests Papua New Guinea
Vanuatu rain forests Solomon Islands, Vanuatu
Vogelkop montane rain forests Indonesia
Vogelkop–Aru lowland rain forests Indonesia
Yapen rain forests Indonesia
Australasian tropical and subtropical dry broadleaf forests ecoregions
Lesser Sundas deciduous forests Indonesia
New Caledonia dry forests New Caledonia
Sumba deciduous forests Indonesia
Timor and Wetar deciduous forests Indonesia, Timor-Leste
Australasian tropical and subtropical grasslands, savannas, and shrublands ecoregions
Arnhem Land tropical savanna Australia
Brigalow tropical savanna Australia
Cape York Peninsula tropical savanna Australia
Carpentaria tropical savanna Australia
Einasleigh Uplands savanna Australia
Kimberley tropical savanna Australia
Mitchell grass downs Australia
Trans-Fly savanna and grasslands Indonesia, Papua New Guinea
Victoria Plains tropical savanna Australia
Australasian temperate broadleaf and mixed forests ecoregions
Chatham Islands temperate forests New Zealand
Eastern Australian temperate forests Australia
Fiordland temperate forests New Zealand
Nelson Coast temperate forests New Zealand
North Island temperate forests New Zealand
Northland temperate kauri forests New Zealand
Stewart Island / Rakiura temperate forests New Zealand
Richmond temperate forests New Zealand
Southeast Australia temperate forests Australia
Southland temperate forests New Zealand
Tasmanian Central Highland forests Australia
Tasmanian temperate forests Australia
Tasmanian temperate rain forests Australia
Westland temperate forests New Zealand
Australasian temperate grasslands, savannas, and shrublands ecoregions
Canterbury–Otago tussock grasslands New Zealand
Southeast Australia temperate savanna Australia
Southwest Australia savanna Australia
Australasian montane grasslands and shrublands ecoregions
Australian Alps montane grasslands Australia
Central Range sub-alpine grasslands Indonesia, Papua New Guinea
Southland montane grasslands New Zealand
Australasian Mediterranean forests, woodlands, and scrub ecoregions
Coolgardie woodlands Australia
Esperance mallee Australia
Eyre and York mallee Australia
Jarrah-Karri forest and shrublands Australia
Swan Coastal Plain scrub and woodlands Australia
Mount Lofty woodlands Australia
Murray-Darling woodlands and mallee Australia
Naracoorte woodlands Australia
Southwest Australia woodlands Australia
Australasian deserts and xeric shrublands ecoregions
Carnarvon xeric shrublands Australia
Central Ranges xeric scrub Australia
Gibson Desert Australia
Great Sandy-Tanami desert Australia
Great Victoria Desert Australia
Nullarbor Plain xeric shrublands Australia
Pilbara shrublands Australia
Simpson Desert Australia
Tirari–Sturt stony desert Australia
Western Australian mulga shrublands Australia
Australasian tundra ecoregions
Antipodes Subantarctic Islands tundra Australia, New Zealand
Australasian mangroves ecoregions
New Guinea mangroves New Guinea
Australian mangroves Australia

See also

References

  1. ↑ "Australasia ecozone". World Wildlife Fund. Archived from the original on 2006-10-07.
  2. ↑ Udvardy, M. D. F. (1975). A classification of the biogeographical provinces of the world. IUCN Occasional Paper no. 18. Morges, Switzerland: IUCN.
  3. ↑ Udvardy, Miklos D. F. (1975) World Biogeographical Provinces (Map). The CoEvolution Quarterly, Sausalito, California. link.
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