Wagner, M.

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[Isolation theory]
The idea that geographical isolation plays an important role in speciation can be traced back to C. Darwin and even earlier. However, it was M. Wagner (1868) who proposed the theory of separations, which states that isolation is not only a secondary role in the sense that natural selection due to different factors operates in geographically different populations, but that isolation itself is a necessary condition for speciation. J. T. Gulick (1872) also collected and studied land snails from the Hawaiian archipelago, and found that there was a great deal of variation in the shape, color, and markings of the shells, and that there were different types in each valley, with nearby valleys being similar to each other and the differences becoming greater the further away they were, and he argued that geographical isolation was important in the differentiation of species and genera. …

*Some of the terminology that mentions "Wagner, M." is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

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［隔離説］
　地理的隔離が種分化に重要な役割を演じているという考えは，古くC.ダーウィンやそれ以前までさかのぼることができる。しかし隔離は地理的に異なった集団には異なった要因による自然淘汰が働くという意味での副次的な役割をもつにとどまらず，隔離こそが種分化の必要条件だとする隔離説Separationstheorieを唱えたのはワーグナーM.Wagner(1868)であった。ギューリックJ.T.Gülick(1872)もハワイ群島の陸産巻貝を集めて研究し，貝の形，色，斑紋について変異が多く，谷ごとに種類が異なり，近くの谷は互いに似ており，遠くなるにつれ違いも大きくなることを明らかにし，種，属の分化に地理的な隔離が重要であると主張した。…

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