>Roy Bateman at 04:51, 2 February 2021

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{{short description|One of the Earth's eight ecozones}}
{{More citations needed|date=April 2012}}
[[File:Ecozone Indomalaya.svg|thumb|400px|The Indomalayan realm]]

The '''Indomalayan realm''' is one of the eight [[biogeographic realm]]s. It extends across most of [[South Asia|South]] and [[Southeast Asia]] and into the southern parts of [[East Asia]].

Also called the '''Oriental realm''' by [[biogeography|biogeographers]], Indomalaya spreads all over the [[Indian subcontinent]] and [[Southeast Asia]] to lowland southern [[China]], and through [[Indonesia]] as far as [[Java (island)|Java]], [[Bali]], and [[Borneo]], east of which lies the [[Wallace line]], the realm boundary named after [[Alfred Russel Wallace]] which separates Indomalaya from [[Australasian realm|Australasia]]. Indomalaya also includes the [[Philippines]], lowland [[Taiwan]], and [[Japan]]'s [[Ryukyu Islands]].

Most of Indomalaya was originally covered by forest, include [[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 forest]]s of Indomalaya are highly variable and diverse, with economically important trees especially in the families [[Dipterocarpaceae]] and [[Fabaceae]].

== Major ecological regions ==

The [[World Wildlife Fund]] (WWF) divides Indomalayan realm into three bio-regions, which it defines as "geographic clusters of eco-regions 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]] and eastern parts of [[Pakistan]]. 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|Sundaland}}
{{main|Ecoregions of 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.

== 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 (unit)|MYA]], carrying its Gondwana-derived flora and fauna northward, which included [[cichlid]] fish and the [[flowering plant]] [[family (biology)|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 [[Australasian realm|Australasia]]. Asian rainforest flora, including the dipterocarps, island-hopped across Wallacea to New Guinea, and several Gondwanian plant families, including [[podocarp]]s and [[araucaria]]s, moved westward from Australia-New Guinea into western Malesia and Southeast Asia.

== Flora ==
Diperocarps (subfamily [[Dipterocarpoideae]]) are characteristic trees of Indomalaya's moist and seasonally dry forests, with the greatest species of diversity in the moist forests of [[Borneo]].<ref>Appanah, Simmathiri and Jennifer M. Turnbull, eds. (1998). ''A Review of Dipterocarps: Taxonomy, ecology and silviculture.'' Center for International Forestry Research, 1998.</ref> Teak (''[[Tectona]]'') is characteristic of the seasonally dry forests of the Indomalaya, from India through Indochina, Malaysia, and the Philippines. Tropical pitcher plants (''[[Nepenthes]]'') are also characteristic of Indomalaya, and the greatest diversity of species is in Sumatra, Borneo, and the Philippines.

The tropical forests of Indomalaya and Australasia share many lineages of plants, which have managed over millions of years to disperse across the straits and islands between Sundaland and New Guinea. The two floras evolved in long isolation, and the fossil record suggests that Asian species dispersed to Australasia starting 33 million years ago as Australasia moved northwards, and dispersal increased 12 million years ago as the two continents approached their present positions. The exchange was asymmetric, with more Indomalayan species spreading to Australasia than Australasian species to Indomalaya.<ref>Ebach, Malte C. (2017). ''Handbook of Australasian Biogeography''. CRC Press, Jan 6, 2017.</ref>

== Fauna ==
Two orders of mammals, the [[colugo]]s (Dermoptera) and [[treeshrew]]s (Scandentia), are [[endemic (ecology)|endemic]] to the realm, as are families Craseonycteridae ([[Kitti's hog-nosed bat]]), [[Diatomyidae]], [[Platacanthomyidae]], Tarsiidae ([[tarsier]]s) and Hylobatidae ([[gibbon]]s). Large mammals characteristic of Indomalaya include the [[leopard]], [[tiger]]s, [[Bubalus|water buffalos]], [[Asian elephant]], [[Indian rhinoceros]], [[Javan rhinoceros]], [[Malayan tapir]], [[orangutan]]s, and [[gibbon]]s.

Indomalaya has three endemic bird families, the Irenidae ([[fairy bluebird]]s), [[Megalaimidae]] and Rhabdornithidae ([[Philippine creeper]]s). Also characteristic are [[pheasant]]s, [[Pitta (bird)|pittas]], [[Old World babbler]]s, and [[flowerpecker]]s.

Indomalaya has 1000 species of [[amphibian]]s in 81 genera, about 17 of global species. 800 Indomalayan species, or 80%, are endemic. Indomalaya has three endemic families of amphibians, [[Nasikabatrachidae]], [[Ichthyophiidae]], and [[Uraeotyphlidae]]. 329, or 33%, of Indomalayan amphibians are considered threatened or extinct, with habitat loss as the principal cause.<ref>Bain, R.H., Biju, S.D., Brown, R.M., Das, I., Diesmos, A.C., Dutta, S.K., Gower, D.J., Inger, R.F., Iskandar, D.T., Kaneko, Y., Neng, M.W., Lau, Meegaskumbura, M., Ohler, A., Papenfuss, T., Pethiyagoda, R., Stuart, B.L., & Wilkinson, M. (2008). ''Amphibians of the Indomalayan Realm''. [https://www.semanticscholar.org/paper/AMPHIBIANS-OF-THE-INDOMALAYAN-REALM-Bain-Biju/b78802b0da3523e3164cc48a35f14ad04e9f0429]</ref>

More information is available under [[:Category:Indomalayan realm fauna|Indomalayan realm fauna]].

== See also ==
* [[Ecoregions of India]]
* [[Ecoregions of the Philippines]]
* [[Mainland Southeast Asia]] (the Indochinese Peninsula)
* [[Malesia]]
* [[Sundaland]]

== Indomalayan ecoregions ==
[[File:Indomalayan biomes.svg|thumb|600px|center|Ecoregions of the Indomalayan realm, color-coded by [[biome]]. Beige: [[deserts and xeric shrublands]]. Light brown: [[tropical and subtropical dry broadleaf forests]]. Green: [[tropical and subtropical moist broadleaf forests]]. Bright green: [[tropical and subtropical coniferous forests]]. light green: [[temperate broadleaf and mixed forests]]. Dark green: [[temperate coniferous forests]]. Light blue: [[flooded grasslands and savannas]]. Light purple: [[montane grasslands and shrublands]]. Magenta: [[mangroves]].]]

{{Indomalayan tropical and subtropical moist broadleaf forests}}
{{Indomalayan tropical and subtropical dry broadleaf forests}}
{{Indomalayan tropical and subtropical coniferous forests}}
{{Indomalayan temperate broadleaf and mixed forests}}
{{Indomalayan temperate coniferous forests}}
{{Indomalayan tropical and subtropical grasslands, savannas, and shrublands}}
{{Indomalayan flooded grasslands and savannas}}
{{Indomalayan montane grasslands and shrublands}}
{{Indomalayan deserts and xeric shrublands}}
{{Indomalaya mangrove}}

==Bibliography==
* 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, [https://books.google.com/books?id=_VGRBWqIG2gC].

==References==
{{Reflist}}

{{commons category|Indomalaya}}
{{Wikivoyage|Wildlife in South and Southeast Asia}}

{{Biomes}}

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[[Category:Indomalayan realm| ]]
[[Category:Biogeographic realms]]
[[Category:Biogeography]]
[[Category:Ecoregions of Asia|.]]
[[Category:Environment of Asia]]
[[Category:Flora of tropical Asia|*]]
[[Category:Natural history of Asia]]
[[Category:Phytogeography]]

Indomalayan realm - Revision history

>Roy Bateman at 04:51, 2 February 2021