Some Comments on the Measurement of Niche Metrics

Abstract

The problem of weighting resource states to make them equally distinct from each other, and thereby improving measures of niche width and overlap, is discussed on the basis of the Colwell—Futuyma (1971) weighting factors. A drawback of their approach appears to be that the distinctness of resource states is not separated from their production in the physical environment. Therefore, a new factor D/P is suggested instead of D, where D stands for the (Colwell—Futuyma) distinctness and P for the production of a resource state. The P value may be approximated by the total number of individuals associated with the resource state, assuming that resources are utilized proportionally to their availability. Information gathered in a study of the community of dung—inhabiting beetles is used in an evaluation of the "summation"and "product" approaches to the estimation of multidimensional niche metrics from unidimensional data. Niche width was measured with the Shannon—Wiener measure, niche overlap with the index of percentage similarity. The multidimensional niche width was well approximated by the summation measure, but the product measure yielded a much better estimate of the multidimensional niche overlap.