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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)."
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.
Sunda shelf and the Philippines
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.
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.
Indomalaya terrestrial ecoregions
|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|
|Wikimedia Commons has media related to Indomalaya.|
- Map of the Indomalaya ecozone . Island Press; Washington, DC.
- Wikramanayake, E., E. Dinerstein, C. J. Loucks, D. M. Olson, J. Morrison, J. L. Lamoreux, M. McKnight, and P. Hedao. 2002. Terrestrial ecoregions of the Indo-Pacific: a conservation assessment. Island Press, Washington, DC, USA, .