Abstract
A new index of species abundance ( ISA ) is described that is calculated for individual species and encompasses numerical abundance and spatial distribution. Data for calculating the ISA is arranged in a two-way table with species composing the rows and columns representing collection sites. The data of the index are ranks and the species in each column are ranked by numerical abundance, with average ranks used for tied scores. A value a is obtained by multiplying the number of zero cells in all columns for each row, by c . One is added to the single largest assigned rank in the columns to obtain c . The sum of ranks, Rj is the summation of assigned ranks in all columns for each row. The ISA is calculated with the formula, $\tt ISA = \frac{\text{a}+R_j}{\text{K}}$ A formula is presented for a standardized ISA , giving indices between 0 and 1. An estimator of standard error for the ISA is described along with an analysis of the components of the ISA and a discussion of practical applications.
Published Version
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