Indomalayan realm

The Indomalayan realm is one of the eight biogeographic realms. It extends across most of South and Southeast Asia and into the southern parts of East Asia.

The Indomalayan realm

Also called the Oriental realm by biogeographers, Indomalaya extends from Afghanistan through the Indian subcontinent and Southeast Asia to lowland southern China, and through Indonesia as far as Java, Bali, and Borneo, east of which lies the Wallace line, the realm boundary named after Alfred Russel Wallace which separates Indomalayan from Australasia. Indomalaya also includes the Philippines, lowland Taiwan, and Japan's Ryukyu Islands.

Most of Indomalaya was originally covered by forest, mostly tropical and subtropical moist broadleaf forests, with tropical and subtropical dry broadleaf forests predominant in much of India and parts of Southeast Asia. The tropical moist forests of Indomalaya are mostly dominated by trees of the dipterocarp family (Dipterocarpaceae).

Major ecological regions

The World Wildlife Fund (WWF) divides Indomalayan realm into three bioregions, which it defines as "geographic clusters of ecoregions that may span several habitat types, but have strong biogeographic affinities, particularly at taxonomic levels higher than the species level (genus, family)."

Indian Subcontinent

The Indian Subcontinent bioregion covers most of India, Bangladesh, Nepal, Bhutan, and Sri Lanka. The Hindu Kush, Karakoram, Himalaya, and Patkai ranges bound the bioregion on the northwest, north, and northeast; these ranges were formed by the collision of the northward-drifting Indian subcontinent with Asia beginning 45 million years ago. The Hindu Kush, Karakoram, and Himalaya are a major biogeographic boundary between the subtropical and tropical flora and fauna of the Indian subcontinent and the temperate-climate Palearctic realm.

Indochina

The Indochina bioregion includes most of mainland Southeast Asia, including Myanmar, Thailand, Laos, Vietnam, and Cambodia, as well as the subtropical forests of southern China.

Sunda shelf and the Philippines

Main article: Sundaland

Malesia is a botanical province which straddles the boundary between Indomalaya and Australasia. It includes the Malay Peninsula and the western Indonesian islands (known as Sundaland), the Philippines, the eastern Indonesian islands, and New Guinea. While the Malesia has much in common botanically, the portions east and west of the Wallace Line differ greatly in land animal species; Sundaland shares its fauna with mainland Asia, while terrestrial fauna on the islands east of the Wallace line are derived at least in part from species of Australian origin, such as marsupial mammals and ratite birds.

History

The flora of Indomalaya blends elements from the ancient supercontinents of Laurasia and Gondwana. Gondwanian elements were first introduced by India, which detached from Gondwana approximately 90 MYA, carrying its Gondwana-derived flora and fauna northward, which included cichlid fish and the flowering plant families Crypteroniaceae and possibly Dipterocarpaceae. India collided with Asia 30-45 MYA, and exchanged species. Later, as Australia-New Guinea drifted north, the collision of the Australian and Asian plates pushed up the islands of Wallacea, which were separated from one another by narrow straits, allowing a botanic exchange between Indomalaya and Australasia. Asian rainforest flora, including the dipterocarps, island-hopped across Wallacea to New Guinea, and several Gondwanian plant families, including podocarps and araucarias, moved westward from Australia-New Guinea into western Malesia and Southeast Asia.

Flora and fauna

Two orders of mammals, the colugos (Dermoptera) and treeshrews (Scandentia), are endemic to the realm, as are families Craseonycteridae (Kitti's Hog-nosed Bat), Diatomyidae, Platacanthomyidae, Tarsiidae (tarsiers) and Hylobatidae (gibbons). Large mammals characteristic of Indomalaya include the leopard, tigers, water buffalos, Asian Elephant, Indian Rhinoceros, Javan Rhinoceros, Malayan Tapir, orangutans, and gibbons.

Indomalaya has three endemic bird families, the Irenidae (leafbirds and fairy bluebirds), Megalaimidae and Rhabdornithidae (Philippine creepers). Also characteristic are pheasants, pittas, Old World babblers, and flowerpeckers.

More information is available under Indomalayan realm fauna.

See also

Malesia
Sundaland
Ecoregions of India
Ecoregions of the Philippines

Indomalaya terrestrial ecoregions

Andaman Islands rain forests India
Borneo lowland rain forests Brunei, Indonesia, Malaysia
Borneo montane rain forests Brunei, Indonesia, Malaysia
Borneo peat swamp forests Brunei, Indonesia, Malaysia
Brahmaputra Valley semi-evergreen forests India
Cardamom Mountains rain forests Cambodia, Thailand, Vietnam
Chao Phraya freshwater swamp forests Thailand
Chao Phraya lowland moist deciduous forests Thailand
Chin Hills-Arakan Yoma montane forests Myanmar, India
Christmas and Cocos Islands tropical forests Australia
Eastern highlands moist deciduous forests India
Eastern Java-Bali montane rain forests Indonesia
Eastern Java-Bali rain forests Indonesia
Greater Negros-Panay rain forests Philippines
Hainan Island monsoon rain forests China
Himalayan subtropical broadleaf forests Bhutan, India, Nepal
Irrawaddy freshwater swamp forests Myanmar
Irrawaddy moist deciduous forests Myanmar
Jiang Nan subtropical evergreen forests China
Kayah-Karen montane rain forests Myanmar, Thailand
Lower Gangetic Plains moist deciduous forests Bangladesh, India
Luang Prabang montane rain forests Laos
Luzon montane rain forests Philippines
Luzon rain forests Philippines
Malabar Coast moist forests India
Maldives-Lakshadweep-Chagos Archipelago tropical moist forests British Indian Ocean Territory, India, Maldives
Meghalaya subtropical forests India
Mentawai Islands rain forests Indonesia
Mindanao montane rain forests Philippines
Mindanao-Eastern Visayas rain forests Philippines
Mindoro rain forests Philippines
Mizoram-Manipur-Kachin rain forests Bangladesh, India, Myanmar
Myanmar coastal rain forests Myanmar
Nansei Islands subtropical evergreen forests Japan
Nicobar Islands rain forests India
North Western Ghats moist deciduous forests India
North Western Ghats montane rain forests India
Northern Annamites rain forests Laos, Vietnam
Northern Indochina subtropical forests China, Laos, Myanmar, Thailand, Vietnam
Northern Khorat Plateau moist deciduous forests Laos, Thailand
Northern Thailand-Laos moist deciduous forests Laos, Thailand
Northern Triangle subtropical forests Myanmar
Northern Vietnam lowland rain forests Vietnam
Orissa semi-evergreen forests India
Palawan rain forests Philippines
Peninsular Malaysian montane rain forests Malaysia, Thailand
Peninsular Malaysian peat swamp forests Malaysia, Thailand
Peninsular Malaysian rain forests Indonesia, Malaysia
Red River freshwater swamp forests Vietnam
South China Sea Islands disputed between China, Malaysia, Philippines, Taiwan, Vietnam
South China-Vietnam subtropical evergreen forests China, Vietnam
South Taiwan monsoon rain forests Taiwan
South Western Ghats moist deciduous forests India
South Western Ghats montane rain forests India
Southern Annamites montane rain forests Cambodia, Laos, Vietnam
Southwest Borneo freshwater swamp forests Indonesia
Sri Lanka lowland rain forests Sri Lanka
Sri Lanka montane rain forests Sri Lanka
Sulu Archipelago rain forests Philippines
Sumatran freshwater swamp forests Indonesia
Sumatran lowland rain forests Indonesia
Sumatran montane rain forests Indonesia
Sumatran peat swamp forests Indonesia
Sundaland heath forests Indonesia
Sundarbans freshwater swamp forests Bangladesh, India
Taiwan subtropical evergreen forests Taiwan
Tenasserim-South Thailand semi-evergreen rain forests Malaysia, Myanmar, Thailand
Tonle Sap freshwater swamp forests Cambodia, Vietnam
Tonle Sap-Mekong peat swamp forests Cambodia, Vietnam
Upper Gangetic Plains moist deciduous forests India
Western Java montane rain forests Indonesia
Western Java rain forests Indonesia
Central Deccan Plateau dry deciduous forests India
Central Indochina dry forests Cambodia, Laos, Thailand, Vietnam
Chota-Nagpur dry deciduous forests India
East Deccan dry evergreen forests India
Irrawaddy dry forests Myanmar
Kathiarbar-Gir dry deciduous forests India
Narmada Valley dry deciduous forests India
Northern dry deciduous forests India
South Deccan Plateau dry deciduous forests India
Southeastern Indochina dry evergreen forests Cambodia, Laos, Thailand
Southern Vietnam lowland dry forests Vietnam
Sri Lanka dry-zone dry evergreen forests Sri Lanka
Himalayan subtropical pine forests Bhutan, India, Nepal, Pakistan
Luzon tropical pine forests Philippines
Northeast India-Myanmar pine forests Myanmar, India
Sumatran tropical pine forests Indonesia
Eastern Himalayan broadleaf forests Bhutan, India, Nepal
Northern Triangle temperate forests Myanmar
Western Himalayan broadleaf forests India, Nepal, Pakistan
Eastern Himalayan subalpine conifer forests Bhutan, India, Nepal
Western Himalayan subalpine conifer forests India, Nepal, Pakistan
Terai-Duar savanna and grasslands Bhutan, India, Nepal
Rann of Kutch seasonal salt marsh India, Pakistan
Kinabalu montane alpine meadows Malaysia
Deccan thorn scrub forests India, Sri Lanka
Indus Valley desert India, Pakistan
Northwestern thorn scrub forests India, Pakistan
Thar desert India, Pakistan
Godavari-Krishna mangroves India
Indochina mangroves Cambodia, Malaysia, Thailand, Vietnam
Indus River Delta-Arabian Sea mangroves Pakistan
Myanmar coast mangroves Myanmar, India, Malaysia, Thailand
Sunda Shelf mangroves Brunei, Indonesia, Malaysia
Sundarbans mangroves Bangladesh, India
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Bibliography

Coordinates: 7°00′N 97°00′E / 7.000°N 97.000°E / 7.000; 97.000

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