Biodiversity and systematics: the use and misuse of divergence information in assessing taxonomic diversity

Abstract

Limited resources for conservation highlight the need for placing priorities on species or other taxa. While priorities or "weightings" based on taxonomic information are now well-established in principle, there is no agreement on a preferred approach. One set of methods attempts to use phylogenetic branch length or divergence information, when available. The "phylogenetic diversity" measure of Faith (1992) uses sums of branch lengths from phylogenetic estimates in order to predict underlying patterns of feature diversity among taxa. An alternative approach suggested by Altschul and Lipman also uses divergence information and would appear to yield results similar to phylogenetic diversity. However, it is demonstrated here that their method in fact can give results opposite to those required if feature diversity is to be maximized. A simple conservation management example, based on mtDNA variation at the population level, illustrates the relative advantage of using phylogenetic diversity to set conservation priorities.