Phylogenetic Diversity and Conservation Priorities under Distinct Models of Phenotypic Evolution

Abstract

Abstract: Phylogenetics sometimes plays a major role in conservation planning, although there are still discussions about what to conserve, the evolutionary novelty revealed by adaptive process or the evolutionary potential expressed by neutral genetic divergence. I discuss the relationship between general models of phenotypic evolution and branch‐length transformations used in phylogenetic diversity (PD) indices. Phylogenetic diversity based on molecular phylogenies will be satisfactory under a neutral model of evolution with constant divergence rates. If evolution of phenotypes occurs under stabilizing or directional selection, however, PD will overestimate and underestimate evolutionary diversity, respectively. I took into account phenotypic patterns in quantitative traits by finding ancestral states and, for each ancestral‐descendent pathway, transforming branch length into amounts of phenotypic evolution before calculating PD. As an example, I applied the method in an evaluation of PD in the eight New World biodiversity hotspots. I based the evaluation on the phylogeny of terrestrial Carnivora and transformed and untransformed (time) branch lengths. In all hotspots, time‐only PD values were larger than their respective phenotypic PD estimates, as expected if stabilizing selection drives most of body size evolution. Both PD estimates were highly correlated with species richness across the hotspots, but the priority ranks changed when loss of species restricted to one hotspot was considered. If phenotypic evolution usually occurs under stabilizing selection processes, conservation efforts and resources would be reduced and/or restricted to a few distinct species with high evolutionary rates, reflecting new adaptive peaks. This may be a liberal conservation strategy, however, compared with PD values calculated from time‐calibrate supertrees or molecular phylogenies, and it is still necessary to understand how adaptive processes drive the evolution of complex phenotypes.