Areas of High Biodiversity Value Evidenced by the Spatial Scaling of Phylogenetic Uniqueness.

Distinct biological communities have high conservation value because they harbour species that cannot be preserved elsewhere. However, community uniqueness is scale-dependent: irreplaceability depends on whether community dissimilarity emerges at small or large spatial scales. To assess conservation value, here we integrate phylogenetic endemism with the spatial scaling of phylogenetic uniqueness in terrestrial vertebrates. We show that phylogenetic endemism is the most efficient single criterion to maximise global phylogenetic diversity within the smallest land area. Moreover, the spatial scaling of phylogenetic uniqueness allows distinguishing globally distinct but regionally less unique sites '(evolutionary hills)', from highly irreplaceable sites even at small scales '(evolutionary islands)', which support lower local diversity but host species that are both evolutionarily unique and threatened. This approach provides a non-heuristic and stable baseline to identify high-value biodiversity areas and offers a powerful tool for prioritising conservation efforts to safeguard evolutionary heritage effectively.