Identifier: ageareastudyinge00will_0 (find matches)
Title: Age and area; a study in geographical distribution and origin of species
Year: 1922 (1920s)
Authors: Willis, J. C. (John Christopher), 1868-1958
Subjects: Biogeography Evolution
Publisher: Cambridge (Eng.) The University press
Contributing Library: Wellesley College Library
Digitizing Sponsor: Boston Library Consortium Member Libraries

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other places. In Brazil it has many endemic species inMinas, the next state to Rio, but on the other and drier sideof the mountains that fringe the coast. This general type of distribution shows very clearly in thecase of very many genera, whether they be endemic genera withall their species in a confined area, like Doona in Ceylon, orwhether they be genera of wide distribution that have developedmany endemic species within a certain small area, like Ranun-culus in New Zealand. In such cases they do not seem as yet tohave encountered any barriers of a very serious kind. But onemay also find a great number of genera, or sections of genera, inwhich the same thing is displayed over a very much larger areathan what would entitle the contained species to be consideredendemic. In Callitris, for example, C. glauca occupies the wholerange of the genus over Australia and Tasmania (130); twoothers range from New South Wales to Tasmania and to West 158 ENDEMISM AND DISTRIBUTION: SPECIES (pt. ii
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ch. xv) ENDEMISM AND DISTRIBUTION: SPECIES 159 Australia, while the remaining 15 species of the genus coversmaller ranges. In Dillenia, D. indica covers practically therange of the genus throughout Indo-Malaya, while there aremany other species covering smaller and smaller ranges withinthis. In Gymnema, G. sylvestre covers almost the whole range ofthe genus from West Africa to Australia, whilst in Cissampelos,C. Pareira is found from tropical America through Africa andAsia to the Philippines, almost covering the whole range of thiscosmotropical genus. In Najas, finally, N. marina is cosmo-politan, while five other species occupy very large areas, nineoccupy areas of moderate size, and seventeen areas of small size. Another very frequent case in endemic genera of small area,or in genera with a number of endemic species within a smallarea, is to have one species occupying a circle of some size,and another a (usually) smaller circle touching, or near to, thefirst, thus giving the impress

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