Ecoregions of Madagascar
Encyclopedia
Madagascar island, located in the Indian Ocean
off the east coast of Africa
, is the fourth largest island in the world. Its long isolation from neighbouring continents allowed the evolution of distinct communities of plants and animals. It is home to five percent of the world's plant
and animal
species
, 80 percent of which are endemic
to Madagascar. Some biogeographers
refer to the island as the "eighth continent", in recognition of its uniqueness and diversity.
and neighboring Indian Ocean
islands form a distinctive sub-region of the Afrotropic
ecozone
in biogeography
, which botanist Armen Takhtajan
called the Madagascan Region. In phytogeography
it is the floristic phytochorion Madagascan Subkingdom in the Paleotropical Kingdom
. The region is charanorth-south along the spine of the island. The Eastern region also included humid pockets further westward, including Sambirano and Isalo
. The Flore sous le vent (leeward flora), now called the Région de l'Ouest (Western Region), lies in the rain shadow
of the central highlands. It includes the drier western and southern portions of the Island, as well as the island's northern tip.
The Eastern and Western regions can be further subdivided into seven terrestrial ecoregions. The Eastern region includes two tropical moist broadleaf forest
ecoregions, the Madagascar lowland forests
along the eastern coastal strip, and the Madagascar subhumid forests
which occupies the highlands above 600-800 meters elevation. At the highest elevations, above 2000 meters, the subhumid forests transition to the Madagascar ericoid thickets
, a montane grasslands and shrublands
ecoregion.
The Madagascar dry deciduous forests
, in the tropical southwest, and the drier Madagascar spiny thickets
occupies the southernmost region of the island.
families are endemic to Madagascar: Asteropeiaceae
, Didymelaceae
, Didiereaceae
, Kaliphoraceae, Melanophyllaceae, Physenaceae
, Sarcolaenaceae
, and Sphaerosepalaceae
. The Seychelles have one endemic plant family, Mesdusagynaceae, and family Psiloxylaceae is endemic to the Macarene Islands.
Before the arrival of humans, Madagascar was home to six lineages of mammals: lemur
s, endemic carnivores
, a pygmy hippopotamus
, tenrecs
, rodents, and bat
s. The lemur
s are thought to be descended from a common ancestor, which crossed to Madagascar over 62 million years ago. Bones of extinct giant lemurs, as large as a gorilla
, have been found on the island.
Recent DNA evidence suggests that Madagascar's eight endemic carnivores, including the Malagasy "mongooses" (Galidia, Galidictis
, Mungotictus, and Salanoia
), fossa
(Cryptoprocta ferox), Falanouc
(Eupleres goudotii), and Malagasy Civet (Fossa fossana), are descended from a single ancestor which crossed from Africa to Madagascar 18-24 million years ago.
17 species of lemurs, including the giant lemur, together with giant tortoise
s, the pygmy hippopotamus, and the elephant bird
, an enormous flightless bird related to the ostrich
, became extinct after the arrival of the human settlers approximately 2000 years ago.
The other islands of the Madagascan region also suffered from waves of extinctions as a result of human arrival on the islands. Numerous bird species, including the famous Dodo
of Mauritius
, became extinct after human settlers arrived. Most of the islands also had one or more species of giant tortoise before humans arrived; 19 of 20 giant tortoise species are presently extinct, and only the Aldabra Giant Tortoise
still survives.
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
off the east coast of Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
, is the fourth largest island in the world. Its long isolation from neighbouring continents allowed the evolution of distinct communities of plants and animals. It is home to five percent of the world's plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
and animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
, 80 percent of which are endemic
Endemic (ecology)
Endemism is the ecological state of being unique to a defined geographic location, such as an island, nation or other defined zone, or habitat type; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. For example, all species of lemur are endemic to the...
to Madagascar. Some biogeographers
Biogeography
Biogeography is the study of the distribution of species , organisms, and ecosystems in space and through geological time. Organisms and biological communities vary in a highly regular fashion along geographic gradients of latitude, elevation, isolation and habitat area...
refer to the island as the "eighth continent", in recognition of its uniqueness and diversity.
Overview
MadagascarMadagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
and neighboring Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
islands form a distinctive sub-region of the Afrotropic
Afrotropic
The Afrotropic is one of the Earth's eight ecozones. It includes Africa south of the Sahara Desert, the southern and eastern fringes of the Arabian Peninsula, the island of Madagascar, southern Iran and extreme southwestern Pakistan, and the islands of the western Indian Ocean. It was formerly...
ecozone
Ecozone
An ecozone is the broadest biogeographic division of the Earth's land surface, based on distributional patterns of terrestrial organisms.Ecozones delineate large areas of the Earth's surface within which organisms have been evolving in relative isolation over long periods of time, separated from...
in biogeography
Biogeography
Biogeography is the study of the distribution of species , organisms, and ecosystems in space and through geological time. Organisms and biological communities vary in a highly regular fashion along geographic gradients of latitude, elevation, isolation and habitat area...
, which botanist Armen Takhtajan
Armen Takhtajan
Armen Leonovich Takhtajan or Takhtajian , was a Soviet-Armenian botanist, one of the most important figures in 20th century plant evolution and systematics and biogeography. His other interests included morphology of flowering plants, paleobotany, and the flora of the Caucasus...
called the Madagascan Region. In phytogeography
Phytogeography
Phytogeography , also called geobotany, is the branch of biogeography that is concerned with the geographic distribution of plant species...
it is the floristic phytochorion Madagascan Subkingdom in the Paleotropical Kingdom
Paleotropical Kingdom
The Paleotropical Kingdom is a floristic kingdom comprising tropical areas of Africa, Asia and Oceania , as proposed by Ronald Good and Armen Takhtajan. Its flora is characterized by about 40 endemic plant families, e.g. Nepenthaceae, Musaceae, Pandanaceae, Flagellariaceae...
. The region is charanorth-south along the spine of the island. The Eastern region also included humid pockets further westward, including Sambirano and Isalo
Isalo
Isalo is a town and commune in Madagascar. It belongs to the district of Miandrivazo, which is a part of Menabe Region. The population of the commune was estimated to be approximately 8,000 in 2001 commune census....
. The Flore sous le vent (leeward flora), now called the Région de l'Ouest (Western Region), lies in the rain shadow
Rain shadow
A rain shadow is a dry area on the lee side of a mountainous area. The mountains block the passage of rain-producing weather systems, casting a "shadow" of dryness behind them. As shown by the diagram to the right, the warm moist air is "pulled" by the prevailing winds over a mountain...
of the central highlands. It includes the drier western and southern portions of the Island, as well as the island's northern tip.
The Eastern and Western regions can be further subdivided into seven terrestrial ecoregions. The Eastern region includes two tropical moist broadleaf forest
Tropical and subtropical moist broadleaf forests
Tropical and subtropical moist broadleaf forests , also known as tropical moist forests, are a tropical and subtropical forest biome....
ecoregions, the Madagascar lowland forests
Madagascar lowland forests
The Madagascar lowland forests are a tropical moist broadleaf forest ecoregion, found on the eastern coast of the island of Madagascar.-Setting:...
along the eastern coastal strip, and the Madagascar subhumid forests
Madagascar subhumid forests
The Madagascar subhumid forests are a tropical moist broadleaf forest ecoregion which originally covered most of the Central Highlands of the island of Madagascar.-Setting:...
which occupies the highlands above 600-800 meters elevation. At the highest elevations, above 2000 meters, the subhumid forests transition to the Madagascar ericoid thickets
Madagascar ericoid thickets
The Madagascar ericoid thickets is a montane shrubland ecoregion, found in the high mountains of Madagascar.The ecoregion covers the area above 1800 meters elevation in separate mountain areas of Madagascar, Tsaratanana , Marojejy , Ankaratra , and Andringitra...
, a montane grasslands and shrublands
Montane grasslands and shrublands
Montane grasslands and shrublands is a biome defined by the World Wildlife Fund. The biome includes high altitude grasslands and shrublands around the world....
ecoregion.
The Madagascar dry deciduous forests
Madagascar dry deciduous forests
The Madagascar dry deciduous forests represent a tropical dry forest ecoregion generally situated in the western part of Madagascar. The area has high numbers of endemic plant and animal species but has suffered large-scale clearance for agriculture...
, in the tropical southwest, and the drier Madagascar spiny thickets
Madagascar spiny thickets
The Madagascar spiny thickets is an ecoregion in Madagascar. The vegetation type is found on poor substrates with low, erratic winter rainfall. An estimated 14,000 to is covered with this habitat, all in the southwest of the country...
occupies the southernmost region of the island.
Endemism and extinction
Eight flowering plantFlowering plant
The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...
families are endemic to Madagascar: Asteropeiaceae
Asteropeiaceae
Asteropeiaceae is the botanical name for a family of flowering plants. Such a family has been recognized by very few taxonomists.The APG II system, of 2003 does recognize such a family and assigns it to the order Caryophyllales in the clade core eudicots...
, Didymelaceae
Didymelaceae
Didymelaceae is a family of flowering plants. The family has been recognised by a fair number of taxonomists, at least over the past few decades....
, Didiereaceae
Didiereaceae
Didiereaceae is a small family of just four genera and 11 species of flowering plants endemic to south and southwest Madagascar, where they form an important component of the Madagascar spiny forests.-Description:...
, Kaliphoraceae, Melanophyllaceae, Physenaceae
Physenaceae
Physenaceae is the botanical name for a family of flowering plants. This family has been only recently recognized by taxonomists.The APG II system, of 2003 , does recognize this family and assigns it to the order Caryophyllales in the clade core eudicots...
, Sarcolaenaceae
Sarcolaenaceae
The Sarcolaenaceae are a family of flowering plants endemic to Madagascar. The family includes 40 species of mostly evergreen trees and shrubs in ten genera....
, and Sphaerosepalaceae
Sphaerosepalaceae
Sphaerosepalaceae is a family of flowering plants. It contains 14 species of trees and shrubs in two genera, Dialyceras and Rhopalocarpus, all of which are endemic to Madagascar. The family is alternatively known as the Rhopalocarpaceae....
. The Seychelles have one endemic plant family, Mesdusagynaceae, and family Psiloxylaceae is endemic to the Macarene Islands.
Before the arrival of humans, Madagascar was home to six lineages of mammals: lemur
Lemur
Lemurs are a clade of strepsirrhine primates endemic to the island of Madagascar. They are named after the lemures of Roman mythology due to the ghostly vocalizations, reflective eyes, and the nocturnal habits of some species...
s, endemic carnivores
Carnivora
The diverse order Carnivora |Latin]] carō "flesh", + vorāre "to devour") includes over 260 species of placental mammals. Its members are formally referred to as carnivorans, while the word "carnivore" can refer to any meat-eating animal...
, a pygmy hippopotamus
Hippopotamus
The hippopotamus , or hippo, from the ancient Greek for "river horse" , is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest...
, tenrecs
Tenrecidae
Tenrecidae is a family of mammals found on Madagascar and parts of Africa. Tenrecs are widely diverse, resembling hedgehogs, shrews, opossums, mice and even otters, as a result of convergent evolution. They occupy aquatic, arboreal, terrestrial and fossorial environments...
, rodents, and bat
Bat
Bats are mammals of the order Chiroptera "hand" and pteron "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, glide rather than fly,...
s. The lemur
Lemur
Lemurs are a clade of strepsirrhine primates endemic to the island of Madagascar. They are named after the lemures of Roman mythology due to the ghostly vocalizations, reflective eyes, and the nocturnal habits of some species...
s are thought to be descended from a common ancestor, which crossed to Madagascar over 62 million years ago. Bones of extinct giant lemurs, as large as a gorilla
Gorilla
Gorillas are the largest extant species of primates. They are ground-dwelling, predominantly herbivorous apes that inhabit the forests of central Africa. Gorillas are divided into two species and either four or five subspecies...
, have been found on the island.
Recent DNA evidence suggests that Madagascar's eight endemic carnivores, including the Malagasy "mongooses" (Galidia, Galidictis
Galidictis
Galidictis is a genus of carnivoran in the family Eupleridae endemic to Madagascar.It contains the following species:* Broad-striped Malagasy Mongoose .* Grandidier's Mongoose ....
, Mungotictus, and Salanoia
Salanoia
Salanoia is a genus of euplerid carnivoran with two currently described species found in Madagascar. They are mongoose-like, which is reflected in the older versions of their English names, for example brown-tailed mongoose which is now called brown-tailed vontsira. The name Salanoia is derived...
), fossa
Fossa (animal)
The fossa is a cat-like, carnivorous mammal that is endemic to Madagascar. It is a member of the Eupleridae, a family of carnivorans closely related to the mongoose family . Its classification has been controversial because its physical traits resemble those of cats, yet other traits suggest a...
(Cryptoprocta ferox), Falanouc
Falanouc
The Falanouc is a rare mongoose-like mammal endemic Malagasy euplerid .It is classified alongside its closest living relative, the Fanaloka, in the subfamily Euplerinae. The Falanouc has several peculiarities which merit its independent classification...
(Eupleres goudotii), and Malagasy Civet (Fossa fossana), are descended from a single ancestor which crossed from Africa to Madagascar 18-24 million years ago.
17 species of lemurs, including the giant lemur, together with giant tortoise
Giant tortoise
Giant tortoises are characteristic reptiles of certain tropical islands. Often reaching enormous size—they can weigh as much as 300 kg and can grow to be 1.3 m long—they live, or lived , in the Seychelles, the Mascarenes and the Galapagos...
s, the pygmy hippopotamus, and the elephant bird
Elephant bird
Elephant birds are an extinct family of flightless birds found only on the island of Madagascar and comprising the genera Aepyornis and Mullerornis.-Description:...
, an enormous flightless bird related to the ostrich
Ostrich
The Ostrich is one or two species of large flightless birds native to Africa, the only living member of the genus Struthio. Some analyses indicate that the Somali Ostrich may be better considered a full species apart from the Common Ostrich, but most taxonomists consider it to be a...
, became extinct after the arrival of the human settlers approximately 2000 years ago.
The other islands of the Madagascan region also suffered from waves of extinctions as a result of human arrival on the islands. Numerous bird species, including the famous Dodo
Dodo
The dodo was a flightless bird endemic to the Indian Ocean island of Mauritius. Related to pigeons and doves, it stood about a meter tall, weighing about , living on fruit, and nesting on the ground....
of Mauritius
Mauritius
Mauritius , officially the Republic of Mauritius is an island nation off the southeast coast of the African continent in the southwest Indian Ocean, about east of Madagascar...
, became extinct after human settlers arrived. Most of the islands also had one or more species of giant tortoise before humans arrived; 19 of 20 giant tortoise species are presently extinct, and only the Aldabra Giant Tortoise
Aldabra Giant Tortoise
The Aldabra giant tortoise , from the islands of the Aldabra Atoll in the Seychelles, is one of the largest tortoises in the world....
still survives.