Island dwarfing

The island gray fox native to the Channel Islands of California as an example of island dwarfing

Fossil skull of Europasaurus holgeri compared to a skull of the related dinosaur Giraffatitan

Island dwarfing is an evolutionary biological phenomenon in which the body size of animal species that live on an island without predators or human interference decreases significantly over generations (" dwarfed ").

The Canadian biologist J. Bristol Foster (* 1932) carried out initial research on island dwarfing . For him, the adaptation mechanisms in the event of overpopulation are the decisive factor as to whether a species tends to dwarf or to island gigantism .

Examples of island dwarfing include:

• Homo floresiensis , anextinct member of the genus Homo discoveredon the island of Flores ,as well as the native inhabitants of anatomically modern humans ( Homo sapiens )living on Flores
• Various, partly extinct dwarf elephant species , including the Borneo Elephant , miniature cultivars of elephant and mammoth on some Mediterranean islands such as the Sicilian dwarf elephant .
• the dwarf mammoth , which was native to the Channel Islands of California and another variety on Wrangel Island .
• Malagasy hippos and hippos on Mediterranean islands.
• the extinct Honshu wolf in Japan .
• the island gray fox in the California Channel Islands . It evolved from the gray fox after specimens of this species came to the northern three Channel Islands. Today this species of real fox is much smaller than the trunk shape, with a body size roughly equivalent to that of a house cat.
• the white-tailed deer .
• Svalbard reindeer on the island of Svalbard are only 65 cm tall, while reindeer on the mainland have an average shoulder height of around 110 cm.
• The phenomenon was also found fossil in the sauropod dinosaur Europaaurus , described in 2006 , which inhabited an island in what is now northern Germany during the late Jurassic period . While closely related forms on the mainland could reach up to 40 meters in length and a weight of 50 to 80 tons , the Europasaurus was already fully grown at about 6.20 meters in length and one ton in weight.

The tendency towards island dwelling can also be seen in raccoons, rabbits, pigs and deer. With a few exceptions, snakes also tend to dwarf islands. Small rodents on islands, on the other hand, tend to be island gigantism. H. Island forms of the animal order tend to develop significantly larger body shapes than on the mainland. The tendency towards gigantic growth can also be observed in iguanas , geckos , skinks and monitor lizards such as the Komodo dragon .

On the Dodecanese island of Tilos , excavations in the Charkadio Cave have uncovered the bones of a dwarf elephant species showing sexual dimorphism . The most recent ¹⁴ C date from the fossil-bearing layer (4390 ± 600 BP uncal) dates between 4340 and 1520 BC. Near. Tilos' pygmy elephant ( Elephas falconeri BUSK ) may not have become extinct until the Bronze Age . Other Neolithic dates come from other Mediterranean islands.

See also

• Deep sea gigantism
• Fouling

literature

• Fr. Bachmayer, Nikolaos K. Symeonidis (1984): The excavations in the dwarf elephant cave on the island of Tilos (Dodecanese, Greece) in 1983. - Session reports of the Academy of Sciences, mathematical and natural science class - 193: 321 - 328.
• J. Bristol Foster: The evolution of mammals on islands. In: Nature . Volume 202, 1964, pp. 234-235.
• Robert H. MacArthur & Edward O. Wilson : The Theory of Island Biogeography. Princeton University Press, Princeton 1967.
• Ted J. Case: A general explanation for insular body size trends in terrestrial vertebrates. In: Ecology. 59, 1978, pp. 1-18.
• Paul AP Durst & V. Louise Roth: Classification tree methods provide a multifactorial approach to predicting insular body size evolution in rodents. In: American Naturalist. Volume 179, No. 4, 2012, pp. 545-553, DOI: 10.1086 / 664611 .
• MR Palombo: Endemic elephants of the Mediterranean Islands: knowledge, problems and perspectives. In: G. Cavarretta (Ed.): La terra degli elefanti. = The world of elephants. Atti del 1. congresso internazionale, Roma, 16–20 October 2001. Consiglio nazionale delle ricerche, Rome 2001, ISBN 88-8080-025-6 , pp. 486–491, online (PDF; 45 kB) .

Web links

Wiktionary: Island dwarfing  - explanations of meanings, word origins, synonyms, translations

• The Observer: Strange world of island species ( Memento from February 10, 2007 in the Internet Archive ) (English, newspaper article about Inselzwergformen, October 31, 2004)

Individual evidence

1. ↑ Serena Tucci et al .: Evolutionary history and adaptation of a human pygmy population of Flores Island, Indonesia. In: Science . Volume 361, No. 6401, 2018, pp. 511–516, doi: 10.1126 / science.aar8486
   Island living can shrink humans. On: sciencemag.org from August 2, 2018
2. ↑ Fr. Bachmayer, N. Symeonidis: The excavations in the dwarf elephant cave on the island of Tilos (Dodecanese, Greece) in 1983 . In: Session reports of the Academy of Sciences, mathematical and scientific class . 193, 1984, pp. 321-328.