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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Effective evolutionary time ： ウィキペディア英語版 Effective evolutionary time The hypothesis of effective evolutionary time〔K. Rohde: Latitudinal gradients in species diversity: the search for the primary cause, Oikos, 65, 514-527,1992.〕 attempts to explain gradients, in particular latitudinal gradients, in species diversity. It was originally named "time hypothesis".〔K. Rohde: Latitudinal gradients in species diversity and their causes. I. A review of the hypotheses explaining the gradients. Biologisches Zentralblatt 97, 393-403, 1978a.〕〔K. Rohde: Latitudinal gradients in species diversity and their causes. II. Marine parasitological evidence for a time hypothesis. Biologisches Zentralblatt 97, 405-418, 1978b.〕 ==Background== Low (warm) latitudes contain significantly more species than high (cold) latitudes. This has been shown for many animal and plant groups, although exceptions exist (see latitudinal gradients in species diversity). An example of an exception is helminths of marine mammals, which have the greatest diversity in northern temperate seas, possibly because of small population densities of hosts in tropical seas that prevented the evolution of a rich helminth fauna, or because they originated in temperate seas and had more time for speciations there. It has become more and more apparent that species diversity is best correlated with environmental temperature and more generally environmental energy. These findings are the basis of the hypothesis of effective evolutionary time. Species have accumulated fastest in areas where temperatures are highest. Mutation rates and speed of selection due to faster physiological rates are highest, and generation times which also determine speed of selection, are smallest at high temperatures. This leads to a faster accumulation of species, which are absorbed into the abundantly available vacant niches, in the tropics. Vacant niches are available at all latitudes, and differences in the number of such niches can therefore not be the limiting factor for species richness. The hypothesis also incorporates a time factor: habitats with a long undisturbed evolutionary history will have greater diversity than habitats exposed to disturbances in evolutionary history. The hypothesis of effective evolutionary time offers a causal explanation of diversity gradients, although it is recognized that many other factors can also contribute to and modulate them. 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「Effective evolutionary time」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.