Conservation evaluation and phylogenetic diversity

Protecting biological diversity with limited resources may require placing conservation priorities on different taxa. A system of priorities that reflects the value of taxonomic diversity can be achieved by setting priorities such that the subset of taxa that is protected has maximum underlying feature diversity. Such feature diversity of taxon subsets is difficult to estimate directly, but can be predicted by the cladistic/phylogenetic relationships among the taxa. In this study, a simple measure of phylogenetic diversity is defined based on cladistic information. The measure of phylogenetic diversity, PD, is contrasted with a measure of taxic diversity recently developed by Vane-Wright et al. (Biol. Conserv., 55, 1991). In re-examining reserve-selection scenarios based on a phylogeny of bumble bees (Apidae), PD produces quite different priorities for species conservation, relative to taxic diversity. The potential application of PD at levels below that of the species is then illustrated using a mtDNA phylogeny for populations of crested newts Triturus cristatus. Calculation of PD for different population subsets shows that protection of populations at either of two extremes of the geographic range of the group can significantly increase the phylogenetic diversity that is protected.