Abstract
The scale of the ongoing biodiversity crisis requires both effective conservation prioritisation and urgent action. As extinction is non-random across the tree of life, it is important to prioritise threatened species which represent large amounts of evolutionary history. The EDGE metric prioritises species based on their Evolutionary Distinctiveness (ED), which measures the relative contribution of a species to the total evolutionary history of their taxonomic group, and Global Endangerment (GE), or extinction risk. EDGE prioritisations rely on adequate phylogenetic and extinction risk data to generate meaningful priorities for conservation. However, comprehensive phylogenetic trees of large taxonomic groups are extremely rare and, even when available, become quickly out-of-date due to the rapid rate of species descriptions and taxonomic revisions. Thus, it is important that conservationists can use the available data to incorporate evolutionary history into conservation prioritisation. We compared published and new methods to estimate missing ED scores for species absent from a phylogenetic tree whilst simultaneously correcting the ED scores of their close taxonomic relatives. We found that following artificial removal of species from a phylogenetic tree, the new method provided the closest estimates of their “true” ED score, differing from the true ED score by an average of less than 1%, compared to the 31% and 38% difference of the previous methods. The previous methods also substantially under- and over-estimated scores as more species were artificially removed from a phylogenetic tree. We therefore used the new method to estimate ED scores for all tetrapods. From these scores we updated EDGE prioritisation rankings for all tetrapod species with IUCN Red List assessments, including the first EDGE prioritisation for reptiles. Further, we identified criteria to identify robust priority species in an effort to further inform conservation action whilst limiting uncertainty and anticipating future phylogenetic advances.
Highlights
We are currently in a period of unprecedented human-mediated biodiversity loss, often termed the ‘sixth mass extinction’ [1]
Where these species are threatened with extinction, they often represent a significant amount of important functional trait diversity that could soon be lost [18,19].The conservation of functional trait diversity is important to maintain ecosystem functioning, the services provided by which—such as food production [20]—are vital to human survival [21,22,23,24].current conservation prioritisation approaches that do not take Phylogenetic Diversity (PD) into consideration may fail to prevent the loss of large amounts of both phylogenetic and functional trait diversity [13,19,25,26,27]
For all three imputation methods (‘original’, ‘simple’ and ‘new’), imputed Evolutionary Distinctiveness (ED) scores of species removed from phylogenies were significantly correlated with the reference ED scores when imputing at a genus level and family level for all three phylogenies
Summary
We are currently in a period of unprecedented human-mediated biodiversity loss, often termed the ‘sixth mass extinction’ [1]. Species with relatively few extant close relatives represent a disproportionate amount of the total PD of their clade [17] Where these species are threatened with extinction, they often represent a significant amount of important functional trait diversity that could soon be lost [18,19].The conservation of functional trait diversity is important to maintain ecosystem functioning, the services provided by which—such as food production [20]—are vital to human survival [21,22,23,24].current conservation prioritisation approaches that do not take PD into consideration may fail to prevent the loss of large amounts of both phylogenetic and functional trait diversity [13,19,25,26,27]. Several metrics have been proposed to integrate PD into the prioritisation of species and regions [12,17,28,29,30,31]
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