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THE OPERATION OF SELECTION IN SITUATIONS OF INTERSPECIFIC COMPETITION

Fundamental to much of community theory is the principle of competitive exclusion which asserts that species overlapping completely in their limiting resource(s) and the manner by which they utilize them cannot co-exist. In the formal theory of interspecific competition upon which this principle is based, little consideration is given to the genetic variability in the competing species. Theories of evolution in situations of species competition also involve primarily ecological considerations and deal with the potential result of this evolution in terms of species similarities rather than with the actual selection process, e.g., MacArthur and Levins (1967). Investigations dealing with selection process often rely on somewhat vague verbal arguments about the nature of the selection mechanism. In a recent investigation dealing with this process, Pimentel et al. (1965) have suggested that through the operation of selection, species completely overlapping in their limiting resource(s) and manner by which they utilize them may co-exist. In this investigation genetic variability is incorporated into the models upon which the principle of competitive exclusion is based. An examination is made of the properties of selection operating on different components of the variability in competitive performance and the effects of this selection on the outcome of interspecific competition. Particular emphasis is given to the conditions under which selection will lead to stable states of co-existence.