Some Observations on the Use of Taxonomic Similarity in Large-Scale Biogeography

Measurement of taxonomic similarity is common in large-scale biogeography. Of the many indices of similarity, those with a probabilistic basis appear to be superior to others in their ability to recognize high and low levels of relationship. Probabilistic indices often are difficult to apply, however, because they require knowledge of the complete species pool from which taxa came to inhabit the various locations and careful formulation of the hypotheses which are to be tested. It cannot be expected that the results of any similarity analysis, no matter how well conceived, lead directly to a unique biogeographic interpretation.