Species Absent






FIGURE 1.8 A performance curve for adaptation of a species along an environmental gradient. (From Furley, P. A. and W. W. Newey. 1988. Geography of the Biosphere: An Introduction to the Nature, Distribution and Evolution of the World's Life Zones. Butterworth & Co., London. With permission.)

develop periodic tables of niches, using Dimitri Mendeleev's periodic table of the chemical elements as a model. This creative idea provides a novel approach for dealing with ecological complexity but it has not been developed.

In contrast to the concept of adaptation, preadaptation is a relatively minor concept of evolutionary biology (Futuyma, 1979; Grant, 1991; Shelley, 1999). Wilson and Bossert (1971) describe it in terms of mutations which initially occur at random:

In other words, within a population with a certain genetic constitution, a mutant is no more likely to appear in an environment in which it would be favored than one in which it would be selected against. When a favored mutation appears, we can therefore speak of it as exhibiting true preadaptation to that particular environment. That is, it did not arise as an adaptive response to the environment but rather proves fortuitously to be adapative after it arises. ... Abundant experimental evidence exists to document the preadaptive nature of some mutants.

Preadaptations are then "preexisting features that make organisms suitable for new situations" (Vogel, 1998). E.P. Odum (1971) cited Thienemann (1926) who termed this the "taking-advantage principle," whereby a species in one habitat can take advantage of an adaptation that developed in a different habitat. Gould (1988) has criticized the name preadaptation as "being a dreadful and confusing term" because "it suggested foresight or planning in the evolutionary process" (Brandon, 1990). However, no such foresight or planning is implied and preadaptation is an apparently random phenomenon in nature. Gould suggests the term exaptation in place of preadaptation, but in this book the old term is retained.

Vogel (1998) has noted "preadaptation may be so common in human technology that no one pays it much attention." As an example, he notes that waterwheels in mills used to extract power from streams were preadapted for use as paddle wheels in the first generation of steamboats. Similarly, the use of preadapted species may

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Growing Soilless

Growing Soilless

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