Similarity measure bias in river benthic Aufwuchs community analysis

An extensive assessment was made of nine common similarity measures on the basis of their discriminative ability and bias in weighting of different types of variation in species abundance between samples, by using sets of river macroinvertebrate samples. Seven ag glomerative hierarchical clustering methods were applied to these measures. Successful site discrimination is defined as grouping of all replicate samples from a particular site. Major differences existed in the discriminative ability between the similarity measures. The measures overweight some types of variation and underweight the others to varying extents, which is closely related to their discriminative ability. A new dissimilarity-similarity measure was devised to respond to all types of variation with minimum bias. This measure yielded a higher percentage of correct site discrimination than the others tested. Use of an extra data set confirmed the superior performance of the new measure and also indicated that it could discriminate between sites of different water quality.