PHYLOGENETIC MEASURES OF BIODIVERSITY - A COMPARISON AND CRITIQUE

Several recent authors have proposed quantitative measures of taxonomic diversity that differ from traditional species-richness and abundance indices. These new methods emphasize phylogenetic branching order and levels of character divergence (including genetic variation) among species. In this study, seven phylogenetic diversity measures are compared using a DNA hybridization data set for cranes. The measures agree in identifying the species that contribute the most and the least to group diversity, but disagree on ranks assigned to species at intermediate levels. Evaluation of alternative measures hinges on the relevance conservationists attach to character divergence beyond its use in reconstructing phylogeny. The use of any such measure is complicated by inconsistency between character sets and disagreement over the definitions of species and subspecies. Until some working consensus is reached on these issues, phylogenetic indices are unlikely to supersede more traditional measures of biodiversity. Substantial effort will be required to integrate phylogenetic diversity with other factors in conservation planning.