The Meanings of Competition

The various meanings of "competition" in ecology, genetics and evolution are grouped into four main meanings which differ in important respects from each other. They grade from a strict meaning to one so broad as to be synonymous with natural selection. In the strict sense competition between animals occurs when a number of animals (of the same or of different species) utilize common resources the supply of which is short; or if the resources are not in short supply competition occurs when the animals seeking that resource nevertheless harm one or another in the process. Intermediate between the strict and the broad meanings are two others. One includes any interference of one species by another irrespective of whether they use common resources or not, and the other includes predation within the meaning of competition. Each of the four meanings of competition is illustrated with examples. A distinction is made between the influence of one species on the numbers of another and the influence of one genotype on the frequency of another genotype of the same species. In the former case one species can influence the frequency of another by competition only when there is a shortage of some resource. The one exception is some special cases of threat. The conclusion is drawn that if the term competition is retained in biological writings it should be restricted to the one strict meaning defined above. On the other hand this may be an appropriate time for approaching the problems of how one organism influences the numbers of another in a fresh way without recourse to the concept of competition at all.