The Indomalayan realm is one of the eight
biogeographic realm
A biogeographic realm is the broadest biogeography, biogeographic division of Earth's land surface, based on distributional patterns of terrestrial animal, terrestrial organisms. They are subdivided into bioregions, which are further subdivid ...
s. It extends across most of
South
South is one of the cardinal directions or compass points. The direction is the opposite of north and is perpendicular to both west and east.
Etymology
The word ''south'' comes from Old English ''sūþ'', from earlier Proto-Germanic ''*sunþa ...
and
Southeast Asia
Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...
and into the southern parts of
East Asia
East Asia is a geocultural region of Asia. It includes China, Japan, Mongolia, North Korea, South Korea, and Taiwan, plus two special administrative regions of China, Hong Kong and Macau. The economies of Economy of China, China, Economy of Ja ...
.
Also called the Oriental realm by
biogeographers, Indomalaya spreads all over the
Indian subcontinent
The Indian subcontinent is a physiographic region of Asia below the Himalayas which projects into the Indian Ocean between the Bay of Bengal to the east and the Arabian Sea to the west. It is now divided between Bangladesh, India, and Pakista ...
and
Southeast Asia
Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...
to lowland southern
China
China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
, and through
Indonesia
Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...
as far as
Sumatra
Sumatra () is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the list of islands by area, sixth-largest island in the world at 482,286.55 km2 (182,812 mi. ...
,
Java
Java is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea (a part of Pacific Ocean) to the north. With a population of 156.9 million people (including Madura) in mid 2024, proje ...
,
Bali
Bali (English:; Balinese language, Balinese: ) is a Provinces of Indonesia, province of Indonesia and the westernmost of the Lesser Sunda Islands. East of Java and west of Lombok, the province includes the island of Bali and a few smaller o ...
, and
Borneo
Borneo () is the List of islands by area, third-largest island in the world, with an area of , and population of 23,053,723 (2020 national censuses). Situated at the geographic centre of Maritime Southeast Asia, it is one of the Greater Sunda ...
, east of which lies the
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 the English biologist Thomas Henry Huxley.
It separates the biogeographic realms of Asia and 'Wallacea', a ...
, the realm boundary named after
Alfred Russel Wallace which separates Indomalaya from
Australasia
Australasia is a subregion of Oceania, comprising Australia, New Zealand (overlapping with Polynesia), and sometimes including New Guinea and surrounding islands (overlapping with Melanesia). The term is used in a number of different context ...
. Indomalaya also includes the
Philippines
The Philippines, officially the Republic of the Philippines, is an Archipelagic state, archipelagic country in Southeast Asia. Located in the western Pacific Ocean, it consists of List of islands of the Philippines, 7,641 islands, with a tot ...
, lowland
Taiwan
Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main geography of Taiwan, island of Taiwan, also known as ''Formosa'', lies between the East China Sea, East and South China Seas in the northwestern Pacific Ocea ...
, and
Japan
Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...
's
Ryukyu Islands
The , also known as the or the , are a chain of Japanese islands that stretch southwest from Kyushu to Geography of Taiwan, Taiwan: the Ryukyu Islands are divided into the Satsunan Islands (Ōsumi Islands, Ōsumi, Tokara Islands, Tokara and A ...
.
Most of Indomalaya was originally covered by forest, and includes
tropical and subtropical moist broadleaf forests
Tropical and subtropical moist broadleaf forests (TSMF), also known as tropical moist forest, is a subtropical and tropical forest habitat type defined by the World Wide Fund for Nature (WWF).
Description
TSMF is generally found in la ...
, with
tropical and subtropical dry broadleaf forests
The tropical and subtropical dry broadleaf forest is a habitat (ecology), habitat type defined by the World Wide Fund for Nature and is located at tropical and subtropical latitudes. Though these forests occur in climates that are warm year-roun ...
predominant in much of India and parts of Southeast Asia. The
tropical forest
Tropical forests are forested ecoregions with tropical climates – that is, land areas approximately bounded by the Tropic of Cancer, tropics of Cancer and Tropic of Capricorn, Capricorn, but possibly affected by other factors such as prevailing ...
s of Indomalaya are highly variable and diverse, with economically important trees, especially in the families
Dipterocarpaceae
Dipterocarpaceae is a family (biology), family of flowering plants with 22 genera and about 695 known species of mainly lowland tropical forest trees. Their distribution is pantropical, from northern South America to Africa, the Seychelles, India ...
and
Fabaceae
Fabaceae () or Leguminosae,[International Code of Nomen ...](_blank)
.
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
The Indian subcontinent is a physiographic region of Asia below the Himalayas which projects into the Indian Ocean between the Bay of Bengal to the east and the Arabian Sea to the west. It is now divided between Bangladesh, India, and Pakista ...
bioregion covers most of
India
India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...
,
Bangladesh
Bangladesh, officially the People's Republic of Bangladesh, is a country in South Asia. It is the List of countries and dependencies by population, eighth-most populous country in the world and among the List of countries and dependencies by ...
,
Nepal
Nepal, officially the Federal Democratic Republic of Nepal, is a landlocked country in South Asia. It is mainly situated in the Himalayas, but also includes parts of the Indo-Gangetic Plain. It borders the Tibet Autonomous Region of China Ch ...
,
Bhutan
Bhutan, officially the Kingdom of Bhutan, is a landlocked country in South Asia, in the Eastern Himalayas between China to the north and northwest and India to the south and southeast. With a population of over 727,145 and a territory of , ...
, and
Sri Lanka
Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka, also known historically as Ceylon, is an island country in South Asia. It lies in the Indian Ocean, southwest of the Bay of Bengal, separated from the Indian subcontinent, ...
and eastern parts of
Pakistan
Pakistan, officially the Islamic Republic of Pakistan, is a country in South Asia. It is the List of countries and dependencies by population, fifth-most populous country, with a population of over 241.5 million, having the Islam by country# ...
. The
Hindu Kush
The Hindu Kush is an mountain range in Central Asia, Central and South Asia to the west of the Himalayas. It stretches from central and eastern Afghanistan into northwestern Pakistan and far southeastern Tajikistan. The range forms the wester ...
,
Karakoram,
Himalaya
The Himalayas, or Himalaya ( ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the Earth's highest peaks, including the highest, Mount Everest. More than 100 pea ...
, 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
The Palearctic or Palaearctic is a biogeographic realm of the Earth, the largest of eight. Confined almost entirely to the Eastern Hemisphere, it stretches across Europe and Asia, north of the foothills of the Himalayas, and North Africa.
Th ...
realm.
Indochina
The Indochina bioregion includes most of mainland
Southeast Asia
Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...
, including
Myanmar
Myanmar, officially the Republic of the Union of Myanmar; and also referred to as Burma (the official English name until 1989), is a country in northwest Southeast Asia. It is the largest country by area in Mainland Southeast Asia and has ...
,
Thailand
Thailand, officially the Kingdom of Thailand and historically known as Siam (the official name until 1939), is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. With a population of almost 66 million, it spa ...
,
Laos
Laos, officially the Lao People's Democratic Republic (LPDR), is the only landlocked country in Southeast Asia. It is bordered by Myanmar and China to the northwest, Vietnam to the east, Cambodia to the southeast, and Thailand to the west and ...
,
Vietnam
Vietnam, officially the Socialist Republic of Vietnam (SRV), is a country at the eastern edge of mainland Southeast Asia, with an area of about and a population of over 100 million, making it the world's List of countries and depende ...
, and
Cambodia
Cambodia, officially the Kingdom of Cambodia, is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. It is bordered by Thailand to the northwest, Laos to the north, and Vietnam to the east, and has a coastline ...
, as well as the subtropical forests of southern
China
China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
.
Sunda Shelf and the Philippines
Malesia
Malesia is a biogeographical region straddling the Equator and the boundaries of the Indomalayan and Australasian realms. It is a phytogeographical floristic region in the Paleotropical kingdom. It was first recognized as a distinct region ...
is a botanical province which straddles the boundary between Indomalaya and Australasia. It includes the
Malay Peninsula
The Malay Peninsula is located in Mainland Southeast Asia. The landmass runs approximately north–south, and at its terminus, it is the southernmost point of the Asian continental mainland. The area contains Peninsular Malaysia, Southern Tha ...
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
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 the English biologist Thomas Henry Huxley.
It separates the biogeographic realms of Asia and 'Wallacea', a ...
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
Marsupials are a diverse group of mammals belonging to the infraclass Marsupialia. They are natively found in Australasia, Wallacea, and the Americas. One of marsupials' unique features is their reproductive strategy: the young are born in a r ...
mammals and
ratite birds.
History
The flora of Indomalaya blends elements from the ancient supercontinents of
Laurasia
Laurasia () was the more northern of two large landmasses that formed part of the Pangaea supercontinent from around ( Mya), the other being Gondwana. It separated from Gondwana (beginning in the late Triassic period) during the breakup of Pa ...
and
Gondwana
Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...
. 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 plant families
Crypteroniaceae and possibly
Dipterocarpaceae
Dipterocarpaceae is a family (biology), family of flowering plants with 22 genera and about 695 known species of mainly lowland tropical forest trees. Their distribution is pantropical, from northern South America to Africa, the Seychelles, India ...
. 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
Australasia is a subregion of Oceania, comprising Australia, New Zealand (overlapping with Polynesia), and sometimes including New Guinea and surrounding islands (overlapping with Melanesia). The term is used in a number of different context ...
. 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
The subfamily
Dipterocarpoideae comprises characteristic tree species in Indomalaya's moist and seasonally dry forests, with the greatest species diversity in the moist forests of
Borneo
Borneo () is the List of islands by area, third-largest island in the world, with an area of , and population of 23,053,723 (2020 national censuses). Situated at the geographic centre of Maritime Southeast Asia, it is one of the Greater Sunda ...
. 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.
Fauna
Two orders of mammals, the
colugos (Dermoptera) and
treeshrews (Scandentia), are
endemic
Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...
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,
tiger
The tiger (''Panthera tigris'') is a large Felidae, cat and a member of the genus ''Panthera'' native to Asia. It has a powerful, muscular body with a large head and paws, a long tail and orange fur with black, mostly vertical stripes. It is ...
s,
water buffalos,
Asian elephant
The Asian elephant (''Elephas maximus''), also known as the Asiatic elephant, is the only living ''Elephas'' species. It is the largest living land animal in Asia and the second largest living Elephantidae, elephantid in the world. It is char ...
,
Indian rhinoceros,
Javan rhinoceros,
Malayan tapir,
orangutans, and
gibbons.
Indomalaya has three endemic bird families, the Irenidae (
fairy bluebirds),
Megalaimidae and Rhabdornithidae (
Philippine creepers). Also characteristic are
pheasant
Pheasants ( ) are birds of several genera within the family Phasianidae in the order Galliformes. Although they can be found all over the world in introduced (and captive) populations, the pheasant genera's native range is restricted to Eura ...
s,
pittas,
Old World babblers, and
flowerpeckers.
Indomalaya has 1000 species of
amphibian
Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excl ...
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.
[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'']
/ref>
More information is available under :Indomalayan realm fauna, Indomalayan realm fauna.
Indomalayan ecoregions
See also
* Ecoregions of India
* Ecoregions of the Philippines
* Mainland Southeast Asia
Mainland Southeast Asia (historically known as Indochina and the Indochinese Peninsula) is the continental portion of Southeast Asia. It lies east of the Indian subcontinent and south of Mainland China and is bordered by the Indian Ocean to th ...
(the Indochinese Peninsula)
* Malesia
Malesia is a biogeographical region straddling the Equator and the boundaries of the Indomalayan and Australasian realms. It is a phytogeographical floristic region in the Paleotropical kingdom. It was first recognized as a distinct region ...
* Sundaland
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
References
{{coord, 7, 00, N, 97, 00, E, source:kolossus-cawiki, display=title
Indomalayan realm,
Biogeographic realms
Biogeography
.
Environment of Asia
*
Natural history of Asia
Phytogeography