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The northern and southern hemispheres of the earth have a dynamic history of advancing and retreating ice sheets. The glacial and interglacial periods are linked to regular eccentricities in the Earth’s orbit and correspond to approximately 100 kyr cycles. The advancing, or glacial periods can cause a massive displacement of flora and fauna as it drives them away from the poles, with the most recent glacial maximum having occurred about 20,000 years ago.,〔Hewitt, Godfrey M. “Some genetic consequences of ice ages, and their role in divergence and speciation.” Biological Journal of the Linnean society. No. 58, 1996. (247-276) 〕〔Ceridwen et al. “Poleward Bound: biological impacts of southern Hemisphere glaciation.” Trends in Ecology and Evolution. Vol. 27, No. 8, August 2012. (462-471) 〕 ==Refugia== While most of the biota were driven away from the poles during the glacial advance, there were still isolated areas of sanctuary. These locations are referred to as refugia. A refugium is defined by Ceridwen et al. as a “geographical area in which populations of glacially impacted organisms persisted during the LGM (Last Glacial Maximum).” Some different types of these areas are coastal, embedded, and periglacial refugia. Coastal refugia are locations of refuge located on uncovered coastal regions or islands. Due to a lower sea level during the last glacial period, it is suspected that the exposed continental shelf played a large role in acting as a refugium to many different organisms as well as potential route for migration.〔Carrara, P.E., et al. “Possible refugia in the Alexander Archipelago of southeastern Alaska during the late Wisconsin glaciation.” Can. J. Earth Sci. 44: 229-244 (2007) 〕 Periglacial refers to refugia located adjacent to a glacier or an ice sheet. Embedded refugia are areas that remained uncovered within the limit of the glacial advance (hot springs or nunataks).〔 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「Examples of refugia」の詳細全文を読む スポンサード リンク
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