John Christopher Willis

John Christopher Willis FRS (20 February 1868 - 21 March 1958) was an English botanist.

Born in Liverpool, he was educated at University College, Liverpool and Gonville and Caius College, Cambridge. In 1896 he was appointed director of the Royal Botanic Gardens, Peradeniya, Ceylon (now Sri Lanka) until 1912 when he was appointed director of the botanic gardens at Rio de Janeiro. He was elected a Fellow of the Linnean Society in 1897, and a Fellow of the Royal Society in 1919. His notable publications include “A Manual and Dictionary of the Flowering Plants and Ferns” in two volumes and “Age and Area: A Study of Geographical Distribution and Origin of Species”, published in 1922. He returned to Cambridge in 1915, and later went to live in Montreaux, Switzerland. He died in 1958 at the age of 90 and was posthumously awarded the Darwin-Wallace Medal by the Linnean Society.

Age and Area

Willis formed the Age and Area hypothesis during botanical field-work in Ceylon where he studied the distributional patterns of the Ceylonese vascular plants in great detail. According to his hypothesis the extent of range of a species may be used as an indication of the age of that species. He also maintained that the "dying out" of species occurs rarely, and that new forms arise by mutation rather than by local adaptation through natural selection. Willis defined his hypothesis as:

The area occupied at any given time, in any given country, by any group of allied species at least ten in number, depends chiefly, so long as conditions remain reasonably constant, upon the ages of the species of that group in that country, but may be enormously modified by the presence of barriers such as seas, rivers, mountains, changes of climates from one region to the next, or other ecological boundaries, and the like, also by the action of man, and by other causes.

The Dutch botanist and geneticist Hugo de Vries supported the hypothesis, however it was criticized by Edward W. Berry who wrote it was contradicted by paleontological evidence. In a paper on the subject in 1924, Berry wrote:

Willis' ideas, it seems to me, are embalmed in a very complicated style, and he makes a great many assertions which are not and can not be substantiated. He claims that the distribution of any species of plant or animal is due solely to the length of time that the species has been in existence, and is not at all dependent on any advantages which it may possess in such matters as production, viability, or dispersal of seeds. Success in life is not dependent on the character of the roots, the nature of the conducting or storage tissues, the form and character of the leaves, the nature of the flowers, or on any other morphological or physiological structures or functions, but is solely a matter of age. In other words, Willis does not believe in those processes which may be grouped under the term adaptation, and he, of course, has no use for natural selection.

Publications

• Studies in the Morphology and Ecology of the Podostemaceæ of Ceylon and India (1902)
• A Manual and Dictionary of the Flowering Plants and Ferns (1908)
• The Distribution of Species in New Zealand (1916)
• The Relative Age of Endemic Species and Other Controversial Points (1917)
• Age and Area. A Study in Geographical Distribution and Origin of Species (1922)
• The Course of Evolution by Differentiation Or Divergent Mutation Rather Than by Selection (1940)

References

• JSTOR: Biographical Memoirs of Fellows of the Royal Society, Vol. 4 (Nov., 1958 ), pp. 353-359 at www.jstor.org

Further reading

• Arnold Miller. (1997). A New Look at Age and Area: The Geographic and Environmental Expansion of Genera Duringthe Ordovician Radiation. Paleobiology, Vol. 23, No. 4, pp. 410-419.