File:Age and area; a study in geographical distribution and origin of species (1922) (14591994339).jpg

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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tus, and Ochnarufescens; on Ritigala (p. 14) three species, on Hinidun-kanda(another somewhat isolated mountain) three, on Adams Peakten, one of which extends into a valley 2000 feet below; and soon. Evidently the investigation of areas occupied bid fair tofurnish interesting information, and I devoted much attentionto it. A careful study of the remaining three-quarters of the 56 AGE AND AREA (pt. endemics showed that they were found upon areas of varioussizes up to the full extent of the dry or the wet zone of Ceylon,or more rarely of both, but that the numbers grew smaller asone went up the scale toward the larger areas. Trimen in hisFlora had rendered yeoman service to the student of areas, byattaching to every species a note to the effect that it was VeryCommon (VC), Common (C), Rather Common (RC), RatherRare (RR), Rare (R), or Very Rare (VR). A study of thelocalities in which species had been found showed that as a rule,though with a good many exceptions, a VR species occurred in
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>iitloonies one place only, or two close together, R in an area about 10-30miles across, RR in one 30-60 miles across, and RC and C inareas larger yet, while VC referred rather to unusual common-ness on areas represented by C. The three diagrams here reproduced give the ranges of anumber of the earlier endemic species in Trimens Flora ofCeylon, belonging to the classes VR, R, and RR. The VR speciesare, it will be seen, usually well localised, though a few (5 in thediagram) have been recorded from two widely separated localities,joined by a wavy line. The R and the RR species, however,cover areas that overlap one another in every possible way, andlook something like the rings in a shirt of chain mail. Nowheredo the areas occupied by two endemic species coincide, except CH. Vl) AGE AND AREA 57 (approximately) in the case of a few VR species, which occurtogether on the same mountain-top. The VR species that occurin the large forests have each their own location. Now a littleconsiderat

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