A Partial Analysis of the Niche

A method is suggested by which the niche hypervolume concept may be used to construct a model useful in the analysis of ecological processes. If a series of separate habitats, in which there is inter-habitat heterogeneity, is examined, the frequency of occurrence of sufficiently or equally vagile species will tend to be correlated with two characteristics: (1) the size of the species' niche hypervolume and, (2) the degree to which hypervolume shape tends to be cubical (spherical). Two methods of computation of versatility indices which provide estimates of relative hypervolumes are used. Both are based on versatility coefficients such that each coefficient represents the (relative) dimension of one of the factors which makes up a species' niche hypervolume. One is based on a ranking procedure and the other on the fraction of the "range of life" of each factor which is included within the toleration limits of the species. Rank difference correlation coefficients comparing the frequency of occurrence of 20 species of common protozoa with their versatility coefficients were positive and significant. Similar comparisons between the coefficient of variation of the versatility coefficients and the frequency of occurrence of the protozoa were negative and significant. These tests suggest that the frequency of occurrence of the most common protozoa species tends to be highest for those species which have largest niche hypervolumes and also tends to be highest for those species which tend to have relatively cubical hypervolumes. The consistency of these observations with theoretical expectation suggests that the proposed indices of versatility and their use in ecological analysis are valid and appropriate. Extension and amplification of analysis of the niche hyperspace model should provide new insights into the ecology and evolution of species.