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A grizzly–polar bear hybrid (also pizzly bear, polizzly, prizzly bear, nanulak, Polar-Grizz, or grolar bear) is a rare ursid hybrid that has occurred both in captivity and in the wild. In 2006, the occurrence of this hybrid in nature was confirmed by testing the DNA of a strange-looking bear that had been shot near Sachs Harbour, Northwest Territories on Banks Island in the Canadian Arctic. Possible wild-bred polar bear-grizzly bear hybrids have been reported and shot in the past, but DNA tests were not available to verify the bears' ancestry. Analyses of DNA sequences of bears have recovered multiple instances of introgressive hybridization between various bear species,〔Verena E Kutschera, Tobias Bidon, Frank Hailer, Julia L. Rodi, Steven R. Fain, Axel Janke (2014) Bears in a Forest of Gene Trees: Phylogenetic Inference Is Complicated by Incomplete Lineage Sorting and Gene Flow. Molecular Biology and Evolution 31(8): 2004–2017. 〕〔Frank Hailer, Verena E. Kutschera, Björn M. Hallström, Denise Klassert, Steven R. Fain, Jennifer A. Leonard, Ulfur Arnason, Axel Janke (2012): Nuclear Genomic Sequences Reveal that Polar Bears Are an Old and Distinct Bear Lineage. Science Vol. 336 no. 6079: 344-347. 〕〔Miller W, Schuster SC, Welch AJ, Ratan A, Bedoya-Reina OC, Zhao F, Kim HL, Burhans RC, Drautz DI, Wittekindt NE, Tomsho LP, Ibarra-Laclette E, Herrera-Estrella L, Peacock E, Farley S, Sage GK, Rode K, Obbard M, Montiel R, Bachmann L, Ingólfsson O, Aars J, Mailund T, Wiig O, Talbot SL, & Lindqvist C (2012). Polar and brown bear genomes reveal ancient admixture and demographic footprints of past climate change. Proceedings of the National Academy of Sciences of the United States of America, 109(36):E2382–E2390. 〕 including introgression of polar bear DNA into brown bears during the Pleistocene. == Occurrences in the wild == With many suspected sightings and three confirmed cases,〔"Alien Ice Bear" UK Channel 5 TV Documentary〕 theories of how such hybrids might naturally occur have become more than hypothetical. Although these two species are genetically similar and often found in the same territories, they tend to avoid each other in the wild. They also fill different ecological niches. Grizzlies (and also Kodiak bears and "Alaskan brown bears", which are all subspecies of the brown bear, ''Ursus arctos''), tend to live and breed on land. Polar bears prefer the water and ice, usually breeding on the ice. The yellowish-white MacFarlane's bear, a mysterious animal known only from one specimen acquired in 1864, seems to attest that grizzly-polar bear hybrids may have always occurred from time to time. Another theory suggests that the polar bears have been driven southward by the melting of the ice cap, bringing them into closer contact with grizzly bears. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Grizzly–polar bear hybrid」の詳細全文を読む スポンサード リンク
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