Taxonomic and phylogenetic distinctiveness in regional conservation assessments: a case study based on extant South African Chiroptera and Carnivora

The current study investigates whether a simple measure of taxonomic diversity (Taxonomic Distinctiveness (TD)) can be used as a proxy for different measures of phylogenetic diversity (Phylogenetic Distinctiveness (PD)) in determining species of regional conservation priority, and uses extant South African Chiroptera and Carnivora as a case study. Published phylogenies for the two mammalian Orders allowed the quantification of a node-based measure that was considered to represent phylogenetic diversity (PD(NODE)), as well as a branch length-based measure that was considered to represent the amount of evolutionary change over time (PD(BRANCH)). Both the PD(NODE) and PD(BRANCH), together with TD were included in our regional conservation priority assessment. Although no statistically significant differences were detected between the PD(NODE), PD(BRANCH) and the TD for both the Chiroptera and Carnivora, these measures were also shown to be correlated with each other. More importantly, inclusion of either the PD(NODE), PD(BRANCH), or TD in our analysis did not significantly alter the species that were identified as being of regional conservation priority. Both regional priority scores for the South African Chiroptera and Carnivora and their respective rankings were broadly consistent across the three potential indicators of conservation status utilised. These results suggest that the inclusion of either the PD(NODE) and/or PD(BRANCH) in conservation prioritisation exercises may not add value to that currently provided by the TD. Consequently, this implies that in the absence of relevant PD data, the utilisation of the TD in regional conservation priority settings may provide the appropriate information on evolutionary diversity.