John Christopher Willis

[1] 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.

In 1901, botanist Johannes Eugenius Bülow Warming published Willisia, which is a genus of flowering plants from India and Bangladesh belonging to the family Podostemaceae.

[4] 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.

[6] 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.

[7]The Dutch botanist and geneticist Hugo de Vries supported the hypothesis; however, it was criticised by the American palaeontologist Edward W. Berry who wrote it was contradicted by palaeontological evidence.

[18] The American ichthyologist Carl Leavitt Hubbs reviewed the book claiming Willis was advocating a form of orthogenesis: Convinced of the failure of natural selection to explain the facts of evolution, distribution, ecology and economic botany, Willis has turned to a compelling internal force, which, "working upon some definite law that we do not yet comprehend" forces a whole population to vary in the same direction.

[19]The American geneticist Sewall Wright similarly noted that Willis believed evolution was not the result of chance but an orthogenetic drive, and that he was a proponent of saltationism.