Compartmentalization and niche differentiation: causal patterns of competition and coexistence

Abstract

The current major models of coexistence of species on the same resources are briefly summarized. It is then shown that analysis of supposedly competitive systems in terms of the physical four dimensions of phase-space is sufficient to understand the causes for coexistence and for competitive exclusion. Thus, the multiple dimensions of niche theory are reduced to factors which define the magnitudes of the phase-spatial system, in particular the boundaries of population spaces and of periods of activity. Excluding possible cooperative interaction between consumers, it appears that coexistence of species on the same kind of limiting resource is possible only in cases of compartmentalization either in space, or in time, of resource consumption, i.e. if each consumer species disposes of a separate resource supply. Three criteria were found to be decisive for successful compartmentalization (i.e. for coexistence): 1. the vector of the resource flow; 2. relative mobility between consumers and resource units; 3. dependence or independence of resource flow on previous consumption. The traditional terminology of niche theory and of competition theory in general proved to be inadequate for analytical treatment of problems of coexistence. © 1987 Kluwer Academic Publishers.