Insular dwarfism 5485600 225173831 2008-07-12T07:58:05Z Jonathan Cardy 4071608 disambig Buffalo [[Image:Cretanelephant-petermaas.jpg|thumb|right|250px|The skeleton of a [[dwarf elephant]] from the island of [[Crete]].]]'''Insular dwarfism''' is the process and condition of the reduction in size of large animals – almost always [[mammal]]s – when their gene pool is limited to a very small environment, primarily islands. This effect has manifested itself many times throughout natural history, including with [[dinosaur]]s and modern animals such as [[elephants]] and [[human being]]s. There are several proposed explanations for the mechanism which produces such dwarfism, which are often considered likely to be co-contributing factors, including an evolved gene-encoded response to environmental stress, as well as a selective process where only the smaller of the animals trapped on the island survive, as food declines to a borderline level. The smaller animals need fewer resources, and so are more likely to get past the break-point where population decline allows food sources to replenish enough for the survivors to flourish. ==Examples== Among the most famous examples of insular dwarfism are: * The [[Channel Islands Mammoth]] which lived on the prehistoric island of [[Santa Rosae]] in the [[California Channel Islands]], and the small [[woolly mammoth]]s of [[Saint Paul Island (Alaska)|Saint Paul Island]] off [[Alaska]], and [[Wrangel Island]] north of [[Siberia]]. * [[Dwarf elephant]]s in the recent natural history of [[Malta]], [[Crete]], [[Cyprus]], and [[Sicily]]. * Dwarf [[stegodon]]s (elephant relatives) from the recent natural history of [[Flores]], [[Sulawesi]], [[Sumba]] and [[Timor]]. * A (disputed) species of [[hominin]] called ''[[Homo floresiensis]]'', from fossils found on [[Flores Island]], [[Indonesia]]. * Small-Bodied [[Human]]s from [[Palau]], [[Micronesia]], similar in size to the Flores hominins.<ref>[http://www.independent.co.uk/news/science/skull-may-identify-tiny-islanders-who-shrank-to-survive-794487.html Skull may identify tiny islanders who shrank to survive], The Independent</ref> * [[Dinosaur]]s, including the recently validated ''[[Europasaurus]]'', on [[Mesozoic]] islands such as [[Haţeg Island]]. There are also proposed instances of this process occurring among plant life, the appearance of dwarf [[sequoia]] / redwood trees being one such proposal.{{Fact|date=June 2007}} This process, and other "[[island genetics]]" artifacts, can occur not only on islands, but also in other situations where an ecosystem is isolated from external resources and breeding. This can include [[caves]], desert [[oases]], and isolated valleys. An example of this is the "[[pygmy]]" people of Africa, such as the [[Mbuti]], who evolved a small size while in genetic and ecological isolation in a dense jungle region.{{Fact|date=May 2008}} There is an inverse form of this process, [[island gigantism]], wherein small animals, lacking the predators of their normal homes, may become "gigantic" when breeding in isolation. An excellent example is the [[dodo]], the ancestors of which were normal-sized [[pigeon]]s. == Additional examples== [[Carnivora]] *[[Channel Island fox]] in [[California]], [[United States]], and the enigmatic, nearly extinct [[Cozumel fox]] *[[Honshū Wolf]] in [[Japan]] *[[Bali Tiger]] *[[Cozumel Island Raccoon]] *[[Sardinian Dhole]] *[[Sardinian Lynx]] [[Ungulate]]s *The strange, tiny [[Balearic Islands]] Cave Goat (''[[Myotragus balearicus]]'') in [[Majorca]] and [[Minorca]] and its close relative ''[[Nesogoral]]'', from [[Sardinia]] which became extinct after human settlement *Philippine [[Bubalus|water buffalo]], [[Tamaraw]], [[Anoa]], the extinct [[Bubalus cebuensis]] and other dwarf [[bovid]]s from South East Asia *Several prehistoric species of [[hippopotamus]] from the Pleistocene of [[Mediterranean]] islands (such as ''[[Phanourios minutis]]'') and [[Madagascar]] *Dwarf [[deer]] species on the Philippines ([[Philippine Sambar]], extant), and Crete (''[[Candiacervus]] ropalophorus''), and Ryukyu Islands of Japan (''Cervus astylodon'') (all extinct) *[[Key Deer]] Other * The tiny flightless [[Inaccessible Island Rail|Inaccessible Island]] and [[Laysan Rail]]s *The dwarf [[nodosaurus|nodosaurid]] ''[[Struthiosaurus]]'' from [[Europe]], and the dwarf [[allosaur]] from South [[Australia]] ==See also== {{wikinews|Bones of "small-bodied humans" found in cave}} *[[Island gigantism]] *[[Foster's rule]] *[[Deep-sea gigantism]] *Baron [[Franz Nopcsa]] ==References== {{reflist}} ==External links== *[http://www.guardian.co.uk/life/science/story/0,12996,1340300,00.html Strange world of island species October 31, 2004 The Observer ] [[Category:Zoology]] [[Category:Paleontology]] [[Category:Ecology]] [[Category:Evolutionary biology]] [[de:Inselverzwergung]] [[es:Enanismo insular]] [[fr:Évolution insulaire]] [[ko:섬의 왜소 발육화]] [[it:Nanismo insulare]] [[tr:Ada cüceleşmesi]] [[uk:Острівна карликовість]]