Phylogenetic Endemism and Conservation Priorities

Abstract

Phylogenetic endemism -- the concentration of evolutionarily unique lineages in restricted geographic ranges -- combines the conservation values of endemism (species found nowhere else) and phylogenetic distinctiveness (species with few close relatives, representing disproportionate evolutionary heritage per species) into a single metric that identifies the most irreplaceable components of the tree of life. Conservation planning based on phylogenetic endemism prioritises areas where losing a species would eliminate the maximum phylogenetic branch length from the global tree of life - rather than areas that simply harbour many species, some of which may have widespread close relatives. This study computed phylogenetic endemism (PE; Faith's PD restricted to endemic species; divided by range size to give weighted PE, WPE) for vascular plants, vertebrates, and invertebrates at 42 Mediterranean and Alpine conservation planning units in Italy, Greece, and Croatia (2,840 species-unit records; from national Red Lists + GBIF; phylogenies from TimeTree v5 and PHYLACINE for vertebrates), identifying WPE hotspots and testing whether current protected area networks capture the highest-WPE areas. WPE hotspots were concentrated in four regions: the Sicilian Mountains, the Central Apennines, the Dinaric Karst (Croatia), and the Aegean islands (Greece) -- consistent with their status as Pleistocene refugia with long in situ diversification histories. Only 38.4% of the top-WPE quartile cells were within protected areas, compared to 48.4% of cells selected by species richness alone -- confirming that current PA networks substantially underprotect phylogenetic endemism. A Phylogenetic Endemism Conservation Priority Index (PECPI) combining WPE, threat status, climate vulnerability, and PA gap identified 14 planning units where single PA expansions would capture the most irreplaceable evolutionary heritage per hectare.