- Ecoregions of Madagascar
Madagascar island , located in theIndian Ocean off the east coast ofAfrica , 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'splant andanimal 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.Overview
Madagascar and neighboring
Indian Ocean islands form a distinctive sub-region of theAfrotropic ecozone , whichbotanist Armen Takhtajan called the Madagascan Region. The region is characterized by numerous endemic taxa of plants and animals, like thelemur s. Madagascar and theSeychelles are fragments of the ancient supercontinent ofGondwana . As Gondwana began to break up 160 million years ago, Madagascar broke away first fromAfrica , and 89 million years ago broke away fromIndia . Many of Madagascar's plant and animal species are of ancient Gondwanan origin. Madagascar remained close to Africa and for a time to India, and some plants and animals were able to cross the straits separating Madagascar from the neighboring continents. The otherIndian Ocean islands, like theComoros andMascarene Islands , are volcanic islands that formed more recently, and were populated by plants and animals from Madagascar, Africa, and the Seychelles.Henri Perrier de la Bâthie (1921) proposed division of Madagascar into two distinctfloristic province s. The "Flore au vent" (windward flora), later called the "Région de l'Est" (Eastern Region), includes those areas receiving the direct influence of the moist southeasttrade wind s, which include the eastern coastal region and the central highlands, which run north-south along the spine of the island. The Eastern region also included humid pockets further westward, includingSambirano andIsalo . The "Flore sous le vent" (leeward flora), now called the "Région de l'Ouest" (Western Region), lies in therain 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, theMadagascar lowland forests along the eastern coastal strip, and theMadagascar subhumid forests which occupies the highlands above 600-800 meters elevation. At the highest elevations, above 2000 meters, the subhumid forests transition to theMadagascar ericoid thickets , amontane grasslands and shrublands ecoregion.The
Madagascar dry deciduous forests , a tropical dry broadleaf forest ecoregion includes western Madagascar and northern tip of the island. Two xeric shrublands regions cover the southwest and south of the island; the dry forests transition to theMadagascar succulent woodlands in the southwest, and the drierMadagascar spiny thickets occupies the southernmost region of the island.Endemism and extinction
Eight
flowering plant families are endemic to Madagascar:Asteropeiaceae ,Didymelaceae ,Didiereaceae ,Kaliphoraceae ,Melanophyllaceae ,Physenaceae ,Sarcolaenaceae , andSphaerosepalaceae . The Seychelles have one endemic plant family,Mesdusagynaceae , and familyPsiloxylaceae is endemic to the Macarene Islands.Before the arrival of humans, Madagascar was home to six lineages of mammals:
lemur s, endemic carnivores, a pygmyhippopotamus , tenrecs,rodents , andbat s. Thelemur s are thought to be descended from a common ancestor, which crossed to Madagascar over 62 million years ago. Bones ofextinct giant lemurs, as large as agorilla , 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)", andMalagasy 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 theelephant bird , an enormous flightless bird related to theostrich , 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 ofMauritius , 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 theAldabra Giant Tortoise still survives.Ecoregions of Madagascar and the Indian Ocean islands
Terrestrial
*
Madagascar lowland forests (Madagascar )
*Madagascar subhumid forests (Madagascar )
*Madagascar dry deciduous forests (Madagascar )
*Madagascar ericoid thickets (Madagascar )
*Madagascar spiny thickets (Madagascar )
*Madagascar succulent woodlands (Madagascar )
*Madagascar mangroves (Madagascar )
*Aldabra Island xeric scrub (Seychelles )
*Comoros forests (Comoros )
*Granitic Seychelles forests (Seychelles )
*Mascarene forests (Mauritius ,Réunion )Freshwater
*
Comoros
*Madagascar Eastern Lowlands
*Madagascar Eastern Highlands
*Madagascar Northwestern Basins
*Madagascar Southern Basins
*Madagascar Western Basins
*Mascarenes
*Coralline Seychelles
*Granitic Seychelles ee also
*
Malagasy fauna
**Endemic birds of Madagascar and western Indian Ocean islands
**List of spiders of Madagascar
*Shifting cultivation
*National parks of Madagascar References
Yoder, A. D.; Burns, M. M.; Zehr, S.; Delefosse, T.; Veron, G.; Goodman, S. M.; Flynn, J. J. 2003. Single origin of Malagasy Carnivora from an African ancestor. "Nature", no. 6924, pp. 734-736.
External links
* [http://www.biodiversityhotspots.org/xp/Hotspots/madagascar/?showpage=Biodiversity Madagascar and the Indian Ocean Islands biodiversity hotspot (Conservation International)]
* [http://www.pbs.org/edens/madagascar/index.htm Madagascar, A World Apart (Public Broadcasting System)]
* [http://www.wildmadagascar.org/ The biological and cultural richness of Madagascar (WildMadagascar.org)]
* [http://www.mobot.org/mobot/madagascar/ Madagascar: Biodiversity and Conservation (Missouri Botanic Garden)]
* [http://www.parcs-madagascar.com Madagascar National Parks] Official site (french only)
Wikimedia Foundation. 2010.