Phylogenetic diversity (PD, total phylogenetic branch length) encapsulates the evolutionary history of species and is a valuable measure of biodiversity because it not only takes into account species richness but also reflects genetic and functional diversity. Therefore, understanding geographic patterns of potential PD loss is essential for biodiversity conservation. Here, we carried out a global assessment of the expected loss in PD from extinctions of current threatened species and identified localities with risk of higher PD loss than expected under random extinction. We considered a total of 4796 terrestrial species for which we had both phylogenetic and geographic data to estimate likely local impacts of global extinctions across space and compare local losses of PD against a model of random extinction. The spatial analysis was carried out based on 100 km by 100 km equally sized cells of the world’s land surface.
Results/Conclusions
If all threatened mammal species go extinct, 22% cells currently harboring threatened species will lose more PD than predicted by random extinction. We also tested for two patterns that might cause some areas to lose more PD than expected. First, if extinction risk in an area is phylogenetically clustered, more internal branches will be lost due to the loss of all their descendant species. Second, if species on longer terminal branches are at higher risk of extinction, more PD will be lost per-extinction, independent of deeper phylogenetic structure. We distinguished the loss of internal branches from loss of terminal branches in grid cells that showed higher than expected loss of PD, and found significant variation in these two processes across space. Overall, our results show that potential losses of PD caused by global species extinctions are linked to spatial location and highlight the value of fine-scaled spatial analysis in assessing impact of global extinctions on biodiversity.
