PHYLOGENETIC MEASURES OF BIODIVERSITY - A COMPARISON AND CRITIQUE

Several recent authors have proposed quantitative measures of taxonomi c diversity that differ from traditional species-richness and abundanc e indices. These new methods emphasize phylogenetic branching order an d levels of character divergence (including genetic variation) among s pecies. In this study, seven phylogenetic diversity measures are compa red using a DNA hybridization data set for cranes. The measures agree in identifying the species that contribute the most and the least to g roup diversity, but disagree on ranks assigned to species at intermedi ate levels. Evaluation of alternative measures hinges on the relevance conservationists attach to character divergence beyond its use in rec onstructing phylogeny. The use of any such measure is complicated by i nconsistency between character sets and disagreement over the definiti ons 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 requi red to integrate phylogenetic diversity with other factors in conserva tion planning.