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Fauna of Africa, in its broader sense, is all the animals living in Africa and its surrounding seas and islands. The more characteristic African fauna is found in the Afrotropical ecoregion.〔R.W. Crosskey, G.B. White, The Afrotropical Region. A recommended term in zoogeography, Journal of Natural History, Vol.11, 5 (1977)〕 Lying almost entirely within the tropics, and equally to north and south of the equator creates favourable conditions for rich wildlife. ==Origins of African fauna== Whereas the earliest traces of life in fossil record of Africa date back to the earliest times,〔F. Westall et al., Implications of a 3.472-3.333Gyr-old subaerial microbial mat from the Barberton greenstone belt, South Africa for the UV environmental conditions on the early Earth, Philosophical Transactions of The Royal Society B, Vol.361, No.1474 (2006)〕 the formation of African fauna as we know it today, began with the splitting up of the Gondwana supercontinent in the mid-Mesozoic era. After that, four to six faunal assemblages, the so-called African Faunal Strata (AFSs) can be distinguished. The isolation of Africa was broken intermittently by discontinuous "filter routes" that linked it to some other Gondwanan continents (Madagascar, South America, and perhaps India), but mainly to Laurasia. Interchanges with Gondwana were rare and mainly "out-of-Africa" dispersals, whereas interchanges with Laurasia were numerous and bidirectional, although mainly from Laurasia to Africa. Despite these connections, isolation resulted in remarkable absences, poor diversity, and emergence of endemic taxa in Africa.〔E. Gheerbrant, J.-C. Rage, Paleobiogeography of Africa: How distinct from Gondwana and Laurasia?. Palaeogeography, Palaeoclimatology, Palaeoecology, Vol 241, 9 Nov. 2006〕 Madagascar separated from continental Africa during the break-up of Gondwanaland early in the Cretaceous, but was probably connected to the mainland again in the Eocene.〔R. McCall, Implications of recent geological investigations of the Mozambique Channel for the mammalian colonization of Madagascar, Proc. R. Soc. Lond. B (1997) 264〕 The first Neogene faunal interchange took place in the Middle Miocene (the introduction of Myocricetodontinae, Democricetodontinae, and Dendromurinae).〔A. J. Winkler, Neogene paleobiogeography and East African paleoenvironments: contributions from the Tugen Hills rodents and lagomorphs. Journal of Human Evolution, Vol 42, January 2002〕 A major terrestrial faunal exchange between North Africa and Europe began at about 6.1 Ma, some 0.4 Myr before the beginning of the Messinian salinity crisis〔M. Benammi et al., Magnetostratigraphy and paleontology of Aït Kandoula basin (High Atlas, Morocco) and the African-European late Miocene terrestrial fauna exchanges. Earth and Planetary Science Letters, Vol 145, Dec 1996〕(for example introduction of Murinae, immigrants from southern Asia)〔A. J. Winkler, Neogene paleobiogeography and East African paleoenvironments: contributions from the Tugen Hills rodents and lagomorphs. Journal of Human Evolution, Vol 42, January 2002〕 During the early Tertiary, Africa was covered by a vast evergreen forest inhabited by an endemic forest fauna with many types common to southern Asia. In the Pliocene the climate became dry and most of the forest was destroyed, the forest animals taking refuge in the remaining forest islands. At the same time a broad land-bridge connected Africa with Asia and there was a great invasion of animals of the steppe fauna into Africa. At the beginning of the Pleistocene a moist period set in and much of the forest was renewed while the grassland fauna was divided and isolated, as the forest fauna had previously been. The present forest fauna is therefore of double origin, partly descended of the endemic fauna and partly from steppe forms that adapted themselves to forest life, while the present savanna fauna is similarly explained. The isolation in past times has resulted in the presence of closely related subspecies in widely separated regions〔E. Lönnberg, The Development and Distribution of the African Fauna in Connection with and Depending upon Climatic Changes. Arkiv for Zoologi, Band 21 A. No.4.1929. pp. 1-33.〕〔J. Fjeldsaå and J.C. Lovett, Geographical patterns of old and young species in African forest biota: the significance of specific montane areas as evolutionary centres. Biodiversity and Conservation, Vol 6, No 3 March 1997〕 Africa, where humans originated, shows much less evidence of loss in the Pleistocene megafaunal extinction, perhaps because co-evolution of large animals alongside early humans provided enough time for them to develop effective defenses.〔Owen-Smith,N. Pleistocene extinctions; the pivotal role of megaherbivores. Paleobiology; July 1987; v. 13; no. 3; p. 351-362〕 Its situation in the tropics spared it also from Pleistocene glaciations and the climate has not changed much.〔P. Brinck. The Relations between the South African Fauna and the Terrestrial and Limnic Animal Life of the Southern Cold Temperate Zone.Proc. Royal Soc. of London. Series B, Vol. 152, No. 949 (1960)〕 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「Fauna of Africa」の詳細全文を読む スポンサード リンク
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