Wallacea

Wallacea is a biogeographical designation for a group of mainly Indonesian islands separated by deep-water straits from the Asian and Australian continental shelves. Wallacea includes Sulawesi, the largest island in the group, as well as Lombok, Sumbawa, Flores, Sumba, Timor, Halmahera, Buru, Seram, and many smaller islands.

The islands of Wallacea lie between Sundaland (the Malay Peninsula, Sumatra, Borneo, Java, and Bali) to the west, and Near Oceania including Australia and New Guinea to the south and east. The total land area of Wallacea is 347,000 km².

Provinces and major islands in Wallacea
Sulawesi
6 provinces
North Maluku, including Halmahera
Maluku, excluding Aru Islands
West Nusa Tenggara
(Lombok, Sumbawa)
East Nusa Tenggara, including
Komodo, Flores, Sumba, West Timor
East Timor (independent)
Map of Sunda and Sahul
The Sahul and Sunda shelves. Wallacea is the area in between.
Indonesia Wallacea
Wallacea is the group of islands within the red area. The Weber Line is in blue.

Geography

The boundary between Sundaland and Wallacea follows the Wallace Line, named after the naturalist Alfred Russel Wallace who recorded the differences between mammal and bird fauna between the islands on either side of the line. The islands of Sundaland to the west of the line, including Sumatra, Java, Bali, and Borneo, share a mammal fauna similar to that of East Asia, which includes tigers, rhinoceros, and apes; whereas the mammal fauna of Lombok and areas extending eastwards are mostly populated by marsupials and birds similar to those in Australasia. Sulawesi shows signs of both.[1]

During the ice ages, sea levels were lower, exposing the Sunda shelf that links the islands of Sundaland to one another and to Asia,[2] and allowed Asian land animals to inhabit these islands. The islands of Wallacea have few land mammals, land birds, or freshwater fish of continental origin, which find it difficult to cross open ocean. Many bird, reptile, and insect species were better able to cross the straits, and many such species of Australian and Asian origin are found there. Wallacea's plants are predominantly of Asian origin, and botanists include Sundaland, Wallacea, and New Guinea as the floristic province of Malaya.

Similarly, Australia and New Guinea to the east are linked by a shallow continental shelf, and were linked by a land bridge during the ice ages, forming a single continent that scientists variously call Australia-New Guinea, Meganesia, Papualand, or Sahul. Consequently, Australia, New Guinea, and the Aru Islands share many marsupial mammals, land birds, and freshwater fish that are not found in Wallacea.[3]

The line dividing Wallacea from Australia–New Guinea is called Lydekker's Line. The Philippines is usually considered a separate region from Wallacea.[4] The Weber Line is the midpoint where Asian and Australian fauna and flora are approximately equally represented, and follows the deepest straits traversing the Indonesian Archipelago.

Biota and conservation issues

Wallacea
A map of Wallacea, bordered by the Wallace and the Lydekker Line.

Although the distant ancestors of Wallacea's plants and animals may have been from Asia or Australia-New Guinea, Wallacea is home to many endemic species. There is extensive autochthonous speciation and proportionately large numbers of endemics; it is an important contributor to the overall mega-biodiversity of the Indonesian archipelago.[5] Because many of the islands are separated from one another by deep water, there is tremendous species diversity among the islands as well.

Fauna species include the endemic anoa (dwarf buffalo) of Sulawesi and the babirusa (deer pig). Maluku shows a degree of species similarity with Sulawesi, but with fewer flora and fauna. Smaller mammals including primates are common. Seram is noted for its butterflies and birdlife including the Amboina king parrot.

Wallacea was originally almost completely forested, mostly tropical moist broadleaf forests, with some areas of tropical dry broadleaf forest. The higher mountains are home to montane and subalpine forests, and mangroves are common in coastal areas. According to Conservation International, Wallacea is home to over 10,000 plant species, of which approximately 1,500 (15%) are endemic.

Endemism is higher among terrestrial vertebrate species; of 1,142 species found there, almost half (529) are endemic. 45% of the region retains some sort of forest cover, and only 52,017 km², or 15 percent, is in pristine state. Of Wallacea's total area of 347,000 km², about 20,000 km² are protected.

Wallacea is home to 82 threatened and six critically endangered species of terrestrial vertebrates.

Ecoregions

Tropical and subtropical moist broadleaf forests

Tropical and subtropical dry broadleaf forests

Distribution between Asia and Australia

Australia may be isolated by sea, but technically through Wallacea, it can be zoologically extended. An example of evidence for when Wallacea formed exists at the Bluff Downs fossil site in northern Australia. Remains of basaltic lava show past oceanic subduction as Australia plowed north through the Pacific. At the site, one of the earliest Australian rodent fossils has been found. Australia's rodents make up much of the continent's placental mammal fauna and include various species from stick-nest rats, hopping mice, and even giant beaver rats. Other mammals invaded the west. Two species of cuscus from Sulawesi are among the most primitive possums in the world and the only marsupials in Asia.

Birds have expanded their range to and from Australia. Crows and shrikes invaded south into New Guinea and some into the Australian continent. Bustards and megapodes must have somehow colonized Australia. Cockatiels similar to those from Australia inhabit Komodo Island in Wallacea.

A few species of Eucalyptus, a predominant genus of trees in Australia, are found in Wallacea: Eucalyptus deglupta on Sulawesi, and E. urophylla and E. alba in East Nusa Tenggara.[6] Interestingly, for land snails Wallacea and Wallace's Line do not form a barrier for dispersal.[7]

Notes

  1. ^ Wallace, Alfred Russel (1869), The Malay Archipelago, pp. 25–29, retrieved 22 Jan 2013
  2. ^ http://www.fieldmuseum.org/research_collections/zoology/zoo_sites/seamaps/mapindex1.htm Pleistocene Sea Level Maps
  3. ^ http://actazool.nhmus.hu/48Suppl2/newwallace.pdf
  4. ^ http://actazool.nhmus.hu/48Suppl2/newwallace.pdf
  5. ^ "Archived copy" (PDF). Archived from the original (PDF) on 2009-03-06. Retrieved 2009-09-26.CS1 maint: Archived copy as title (link) page 3-2
  6. ^ Irfan Budi Pramono and Ag. Pudjiharta (1996). "Research Experiences on Eucalyptus in Indonesia," in Reports submitted to the regional expert consultation on eucalyptus, Vol. II. Food and Agriculture Organization, Regional Office for Asia and the Pacific, Bangladesh.
  7. ^ Hausdorf, B. (2019). "Beyond Wallace's line – dispersal of Oriental and Australo-Papuan land-snails across the Indo-Australian Archipelago". Zoological Journal of the Linnean Society. 185 (1): 66–76. doi:10.1093/zoolinnean/zly031.

References

  • Abdullah MT. (2003). Biogeography and variation of Cynopterus brachyotis in Southeast Asia. PhD thesis. University of Queensland, St Lucia, Australia.
  • Corbet, GB, Hill JE. (1992). The Mammals of the Indomalayan Region: A Systematic Review. Oxford University Press, Oxford.
  • Hall LS, Gordon G. Grigg, Craig Moritz, Besar Ketol, Isa Sait, Wahab Marni and M.T. Abdullah. (2004). "Biogeography of fruit bats in Southeast Asia." Sarawak Museum Journal LX(81):191–284.
  • Wilson DE, Reeder DM. (2005). Mammal Species of the World. Smithsonian Institution Press, Washington, D.C.

External links

Australasian realm

The Australasian realm is a biogeographic realm that is coincident, but not synonymous (by some definitions), with the geographical region of Australasia. The realm includes Australia, the island of New Guinea (including Papua New Guinea and the Indonesian province of Papua), and the eastern part of the Indonesian archipelago, including the island of Sulawesi, the Moluccan islands (the Indonesian provinces of Maluku and North Maluku) and 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.From an ecological perspective the Australasian realm is a distinct region with a common geologic and evolutionary history and 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 biological dividing line from the Indomalayan realm of tropical Asia is the Wallace Line: Borneo and Bali lie on the western, Asian side.

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.

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.

Babirusa

The babirusas, also called deer-pigs (Indonesian: babirusa) are a genus, Babyrousa, in the swine family found in Wallacea, or specifically the Indonesian islands of Sulawesi, Togian, Sula and Buru. All members of this genus were considered part of a single species until 2002, the babirusa, B. babyrussa, but following the split into several species, this scientific name is restricted to the Buru babirusa from Buru and Sula, whereas the best-known species, the north Sulawesi babirusa, is named B. celebensis. The remarkable "prehistoric" appearance of these mammals is largely due to the prominent upwards incurving canine tusks of the males, which actually pierce the flesh in the snout.All species of babirusa are listed as threatened by the International Union for Conservation of Nature (IUCN), shown on their Red List since at least 2010 and current in 2017.

Cacatua (subgenus)

Cacatua is a subgenus of the white cockatoos (genus Cacatua). They are found in wooded habitats from Wallacea east to the Bismarck Archipelago and south to Australia. With the exception of the yellow-crested cockatoo, all are relatively large cockatoos with a total length of 45–55 cm (18–22 in). Their plumage is mainly white (tinged pinkish in the salmon-crested cockatoo), and the underwing and -tail have a yellowish tinge. Their crest is expressive and brightly coloured in most species. Unlike the members of the subgenus Licmetis, the members of the subgenus Cacatua have a black bill.

The sulphur-crested cockatoo is relatively widespread and can even be seen in suburban habitats in some parts of its range, but the remaining members of this subgenus all have relatively small distributions and are considered threatened by the IUCN due to a combination of habitat loss and capture for the wild bird trade.

Cinnamon-tailed fantail

The cinnamon-tailed fantail (Rhipidura fuscorufa) is a fantail restricted to the Banda Sea Islands of Indonesia.

Dusky moorhen

The dusky moorhen (Gallinula tenebrosa) is a bird species in the rail family and is one of the eight extant species in the moorhen genus. It occurs in India, Australia, New Guinea, Borneo and Indonesia. It is often confused with the purple swamphen and the Eurasian coot due to similar appearance and overlapping distributions. They often live alongside birds in the same genus, such as the Tasmanian nativehen and the common moorhen.

Elegant imperial pigeon

The elegant imperial pigeon, (Ducula concinna) also known as blue-tailed imperial-pigeon, is a large (43 cm in length) pigeon, with upperparts mainly dark blue-green in colour with an iridescent sheen. Head, neck and underparts are mostly pale grey, with red-brown undertail coverts.

Fauna of Indonesia

The fauna of Indonesia is characterised by high levels of biodiversity and endemicity due to its distribution over a vast tropical archipelago. Indonesia divides into two ecological regions; western Indonesia which is more influenced by Asian fauna, and the east which is more influenced by Australasian species.

The Wallace Line, around which lies the Wallacea transitional region, notionally divides the two regions. There is diverse range of ecosystems, including beaches, sand dunes, estuaries, mangroves, coral reefs, sea grass beds, coastal mudflats, tidal flats, algal beds, and small island ecosystems.

Environmental issues due to Indonesia's rapid industrialisation process and high population growth, have seen lower priority given to preserving ecosystems. Issues include illegal logging, with resulting deforestation, and a high level of urbanisation, air pollution, garbage management and waste water services also contributing to the forest deterioration.

Great-billed parrot

The great-billed parrot (Tanygnathus megalorynchos) also known as Moluccan parrot or island parrot, is a medium-sized, approximately 38 cm long, green parrot with a massive red bill, cream iris, blackish shoulders, olive green back, pale blue rump and yellowish green underparts. The female is typically smaller than the male, but otherwise the sexes are similar.

The great-billed parrot is found in forest, woodland and mangrove in the south-east Asian islands of Maluku, Raja Ampat, Talaud, Sangir, Sarangani, the Lesser Sundas, and nearby small islands. The diet consists mainly of fruits.

It remains widespread and locally fairly common, and consequently has been rated as least concern on the IUCN Red List of Threatened Species.

Indigenous people of New Guinea

The indigenous peoples of New Guinea, commonly called Papuans, are Melanesians. There is genetic evidence for two major historical lineages in New Guinea and neighboring islands: a first wave from the Malay archipelago perhaps 50,000 years ago when New Guinea and Australia were a single landmass called Sahul, and much later a wave of Austronesian people from the north who introduced Austronesian languages and pigs about 3,500 years ago, and who left a small but significant genetic trace in many coastal Papuan peoples (though only a minority of Austronesian-speaking Papuans have detectable Austronesian ancestry). Linguistically, Papuans speak languages from the many families of non-Austronesian languages which are found only on New Guinea and neighboring islands, Austronesian languages along parts of the coast, and recently developed creoles such as Tok Pisin and Papuan Malay.

The people of New Guinea also include more recent immigrants, especially on the Indonesian side of the island, where recent migrants comprise up to half of the population.

The term "Papuan" is used in a wider sense in linguistics and anthropology. In linguistics, "Papuan languages" is a cover term for the diverse mutually unrelated non-Austronesian language families spoken in Melanesia and parts of Wallacea. In anthropology, "Papuan" is often used to denote the highly diverse populations of Melanesia and Wallacea prior to the advent of Austronesian-speakers, and the dominant genetic traces of these populations in the current ethnic groups of these areas.

Laili (cave)

Laili is a limestone cave located near the town of Laleia, Manatuto District, East Timor. Archeological findings in Laili provide evidence that the cave was occupied by modern humans 44,600 years ago, making it the oldest known such habitation in Wallacea.The age of findings made in Laili corroborates the theory that humans spread from Asia to Australia through the Southern route, via Java and the Lesser Sunda Islands.

Lesser Sunda Islands

The Lesser Sunda Islands (Indonesian: Kepulauan Nusa Tenggara "southeastern archipelago"

or Kepulauan Sunda Kecil "lesser Sundanese archipelago")

are a group of islands in Maritime Southeast Asia, north of Australia. Together with the Greater Sunda Islands to the west they make up the Sunda Islands. The islands are part of a volcanic arc, the Sunda Arc, formed by subduction along the Sunda Trench in the Java Sea.

The main Lesser Sunda Islands are, from west to east: Bali, Lombok, Sumbawa, Flores, Sumba, Timor, Alor archipelago, Barat Daya Islands, and Tanimbar Islands.

Malesia

Malesia is a biogeographical region straddling the Equator and the boundaries of the Indomalaya ecozone and Australasia ecozone, and also a phytogeographical floristic region in the Paleotropical Kingdom. It has been given different definitions. The World Geographical Scheme for Recording Plant Distributions split off Papuasia in its 2001 version.

Maluku Islands

The Maluku Islands or the Moluccas () are an archipelago in eastern Indonesia. Tectonically they are located on the Halmahera Plate within the Molucca Sea Collision Zone. Geographically they are located east of Sulawesi, west of New Guinea, and north and east of Timor.

The islands were known as the Spice Islands due to the nutmeg, mace and cloves that were originally exclusively found there, the presence of which sparked colonial interest from Europe in the sixteenth century.The Maluku Islands formed a single province from Indonesian independence until 1999, when it was split into two provinces. A new province, North Maluku, incorporates the area between Morotai and Sula, with the arc of islands from Buru and Seram to Wetar remaining within the existing Maluku Province. North Maluku is predominantly Muslim, and its capital is Sofifi on Halmahera island. Maluku province has a larger Christian population, and its capital is Ambon. Though originally Melanesian, many island populations, especially in the Banda Islands, were massacred in the seventeenth century during the spice wars. A second influx of immigrants primarily from Java began in the early twentieth century under the Dutch and continues in the Indonesian era.

Between 1999 and 2002, conflict between Muslims and Christians killed thousands and displaced half a million people.

Metallic pigeon

The metallic pigeon, (Columba vitiensis) also known as white-throated pigeon is a medium-sized, up to 37 cm long, bird in the family Columbidae.

Pale-headed munia

The pale-headed munia (Lonchura pallida) is a species of estrildid finch found in Indonesia. It is found in artificial landscapes, subtropical and tropical lowlands, dry shrubland and grassland habitat. The status of the species is evaluated as Least Concern.

Spotted whistling duck

The spotted whistling duck (Dendrocygna guttata) is a member of the duck family Anatidae.

It is distributed throughout the southern Philippines, Wallacea and New Guinea. It has recently colonised Australia, with a small population now resident at Weipa on the western coast of Cape York Peninsula.

Sula megapode

The Sula megapode or Sula scrubfowl (Megapodius bernsteinii) is a species of bird in the family Megapodiidae. It is found only in the Banggai and Sula Islands between Sulawesi and the Maluku Islands in Indonesia, where its habitats are subtropical or tropical dry forest, subtropical or tropical moist lowland forest, subtropical or tropical mangrove forest, and subtropical or tropical moist shrubland. It is threatened by habitat destruction.

Tawny grassbird

The tawny grassbird (Cincloramphus timoriensis) is a songbird species of the grass- and bush-warbler family (Locustellidae). It was formerly placed in the "Old World warbler" assemblage.

It is found in Australia, Indonesia, Papua New Guinea, and the Philippines.

Wallace Line

The Wallace Line or Wallace's Line is a faunal boundary line drawn in 1859 by the British naturalist Alfred Russel Wallace and named by English biologist Thomas Henry Huxley, that separates the ecozones of Asia and Wallacea, a transitional zone between Asia and Australia. West of the line are found organisms related to Asiatic species; to the east, a mixture of species of Asian and Australian origin is present. Wallace noticed this clear division during his travels through the East Indies in the 19th century.

The line runs through Indonesia, between Borneo and Sulawesi (Celebes), and through the Lombok Strait between Bali and Lombok. The distance between Bali and Lombok is small, about 35 kilometres (22 mi). The distributions of many bird species observe the line, since many birds do not cross even the shortest stretches of open ocean water. Some bats have distributions that cross the line, but larger terrestrial mammals are generally limited to one side or the other; exceptions include macaques, pigs and tarsiers on Sulawesi. Other groups of plants and animals show differing patterns, but the overall pattern is striking and reasonably consistent. Flora do not follow the Wallace Line to the same extent as fauna. One genus of plants which does not cross the Line is the Australasian genus Eucalyptus.

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