2010年7月3日星期六

Quagga






The quagga (Equus quagga quagga) is an extinct subspecies of the Plains zebra,which was once found in great numbers in South Africa's Cape Province and the southern part of the Orange Free State. It was distinguished from other zebras by having the usual vivid marks on the front part of the body only. In the mid-section, the stripes faded and the dark, inter-stripe spaces became wider, and the rear parts were a plain brown. The name comes from a Khoikhoi word for zebra and is onomatopoeic, being said to resemble the quagga's call. The only quagga to have been photographed alive was a mare at the Zoological Society of London's Zoo in Regent's Park in 1870.

The quagga lived in the drier parts of South Africa, on grassland. The northern limit seems to have been the Orange River in the west and the Vaal River in the east; the south-eastern border may have been the Great Kei River. It was hunted for its meat and hide, and is one of the many victims of modern mass extinction.

The quagga was originally classified as an individual species, Equus quagga, in 1778. Over the next 50 years or so, many other zebras were described by naturalists and explorers. Because of the great variation in coat patterns (no two zebras are alike), taxonomists were left with a great number of described "species", and no easy way to tell which of these were true species, which were subspecies, and which were simply natural variants.

Long before this confusion was sorted out, the quagga had been hunted to extinction for meat, hides, and to preserve feed for domesticated stock. The last wild quagga was probably shot in the late 1870s, and the last specimen in captivity, a mare, died on August 12, 1883 at the Artis Magistra zoo in Amsterdam. Because of the confusion between different zebra species, particularly among the general public, the quagga had become extinct before it was realized that it appeared to be a separate species.

The quagga was the first extinct creature to have its DNA studied. Recent genetic research at the Smithsonian Institution has demonstrated that the quagga was in fact not a separate species at all, but diverged from the extremely variable plains zebra, Equus burchelli, between 120,000 and 290,000 years ago, and suggests that it should be named Equus burchelli quagga. However, according to the rules of biological nomenclature, where there are two or more alternative names for a single species, the name first used takes priority. As the quagga was described about thirty years earlier than the plains zebra, it appears that the correct terms are E. quagga quagga for the quagga and E. quagga burchelli for the plains zebra, unless "Equus burchelli" is officially declared to be a nomen conservandum.

After the very close relationship between the quagga and surviving zebras was discovered, the Quagga Project was started by Reinhold Rau in South Africa to recreate the quagga by selective breeding from plains zebra stock, with the eventual aim of reintroducing them to the wild. This type of breeding is also called breeding back. In early 2006, it was reported that the third and fourth generations of the project have produced animals which look very much like the depictions and preserved specimens of the quagga, though whether looks alone are enough to declare that this project has produced a true "re-creation" of the original quagga is controversial.

DNA from mounted specimens was successfully extracted in 1984, but the technology to use recovered DNA for breeding does not yet exist. In addition to skins such as the one held by the Natural History Museum in London, there are 23 known stuffed and mounted quagga throughout the world. A twenty-fourth specimen was destroyed in Königsberg, Germany (now Kaliningrad), during World War II.

没有评论:

发表评论