Neoendemism

Neoendemism is one of two sub-categories of endemism, the ecological state of a species being unique to a defined geographic location. Specifically, neoendemic species are those that have recently arisen, through divergence and reproductive isolation or through hybridization and polyploidy in plants. Paleoendemism, the other sub-category, refers to species that were formerly widespread but are now restricted to a smaller area.

Examples

Darwin's finches.jpeg
Four of the 14 finch species found on the Galápagos Archipelago

"Darwin's finches", residents of the Galápagos Islands, have been used since the 19th century as an example of how the descendants of one ancestor can evolve through adaptive radiation into several species as they adapt to different conditions on various islands. Charles Darwin wrote:

...one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends."[1][2]

The Galápagos archipelago is also the home of paleoendemic species.[3]

See also

Notes

  1. ^ Darwin 1845, pp. 379–380
  2. ^ Darwin 1887
  3. ^ Waller, Thomas. "The evolutionary and biogeographic origins of the endemic Pectinidae (Mollusca: Bivalvia) of the Galápagos Islands (abstract)". Journal of Paleontology. 81: 929–950. doi:10.1666/pleo05-145.1.

References

  • Darwin, Charles (1845), Journal of researches into the natural history and geology of the countries visited during the voyage of H.M.S. Beagle round the world, under the Command of Capt. Fitz Roy, R.N (2nd. ed.), London: John Murray
  • Darwin, Francis (1887), "Chapter 1, The Foundations of the 'Origin of Species'", in Darwin, Francis (ed.), The life and letters of Charles Darwin, including an autobiographical chapter, 2, London: John Murray, PMC 2604052
Endemism

Endemism is the ecological state of a species being unique to a defined geographic location, such as an island, nation, country 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. The extreme opposite of endemism is cosmopolitan distribution. An alternative term for a species that is endemic is precinctive, which applies to species (and subspecific categories) that are restricted to a defined geographical area.

Flora of Madagascar

The flora of Madagascar consists of more than 12,000 species of vascular and non-vascular plants. Although fungus, lichens and algae are no longer included in the Plant Kingdom, they are discussed here as well. Around 83% of Madagascar's vascular plants are found only on the island. These endemics include five plant families, 85% of the over 900 orchid species, around 200 species of palms, and such emblematic species as the traveller's tree, six species of baobab and the Madagascar periwinkle. The high degree of endemism is due to Madagascar's long isolation following its separation from the African and Indian landmasses in the Mesozoic, 150–160 and 84–91 million years ago, respectively. However, few plant lineages remain from the ancient Gondwanan flora; most extant plant groups immigrated via across-ocean dispersal well after continental break-up.

After its continental separation, Madagascar probably experienced a dry period, and tropical rainforest expanded only later in the Oligocene to Miocene when rainfall increased. Today, humid forests, including the lowland forests, are mainly found on the eastern plateau where abundant rainfall from the Indian Ocean is captured by an escarpment. A large part of the central highlands, in the sub-humid forests ecoregion, is today dominated by grasslands. They are widely seen as result of human landscape transformation but some may be more ancient. Grassland occurs in a mosaic with woodland and bushland, including tapia forest, and hard-leaved thickets on the high mountains. Dry forest and succulent woodland are found in the drier western part and grade into the unique spiny thicket in the southwest, where rainfall is lowest and the wet season shortest. Mangroves occur on the west coast, and a variety of wetland habitats with an adapted flora are found across the island.

The first human presence in Madagascar dates only 2000–4000 years back, and settlement in the interior occurred centuries later. The Malagasy people have used the native flora for various purposes, including food, construction, and medicine. Exotic plants were introduced by early settlers, later traders and French colonialists, and many have become important to agriculture. Among them are rice, the staple dish of Malagasy cuisine grown in terraced fields in the highlands, and greater yam, taro, cowpea, and plantain. Plantation crops include litchi, cloves, coffee, and vanilla, the latter one of the country's main export produce today. More than 1,300 introduced plants are known, of which around 600 have become naturalised, and some invasive.

Human population growth and economic activity have put pressure on natural vegetation in the region, especially through massive deforestation. Madagascar's high endemism and species richness coupled with a sharp decrease in primary vegetation make the island a global biodiversity hotspot. To preserve natural habitats, around 10% of the land surface is protected, including the World Heritage sites Tsingy de Bemaraha and the Rainforests of the Atsinanana. While historically mainly French naturalists described Madagascar's flora, today a number of national and international herbaria, botanical gardens and universities document plant diversity and engage in its conservation.

Paleoendemism

Paleoendemism along with neoendemism is one of two sub-categories of endemism. Paleoendemism refers to species that were formerly widespread but are now restricted to a smaller area.

Neoendemism refers to species that have recently arisen, such as through divergence and reproductive isolation or through hybridization and polyploidy in plants.

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