A Table for Calculating the `Equitability' Component of Species Diversity

Abstract

We recognize two distinct components of species diversity: the number of species and the "equitability" with which the individuals are apportioned among the species. A quantitative expression for "equitability" per se is derived from the Shannon-Wiener function of information theory, using MacArthur''s "broken-stick" model as a yardstick, and a table is provided which greatly reduces the necessary calculations. The appropriate use of this formula, and the sampling problems, depend very much on whether one is trying to describe the local conditions of association under which the animals are living or whether one is interested in characterizing the fauna of a large area as a whole.