Conservation priorities for Diprotodonts according to evolutionary distinctiveness and extinction risk

Diprotodontia is an order of mammals that has received comparatively less attention in conservation research than others. With more than 75% nationally endemic species, Diprotodontia is threatened to lose, in the near future, a high proportion of its species and more phylogenetic diversity than expected from random extinction. In this study, we prioritized Diprotodontia species with high conservation values by evolutionary distinctiveness and extinction probability, which are two important criteria in the prioritization system. We measured evolutionary distinctiveness first by a widely-used index (named ED) and its recently improved version (ED2) that both exhibited a biased view of evolutionary distinctiveness toward the terminal branch length in a phylogenetic tree. Then we measured it by recently developed parametric indices (named \({}^{\alpha }\Delta {eq}^{*}\) and ^αδ) that offered gradual changes in views from terminal branch length to the global shape of the tree. We also used indices that combine a species’ evolutionary distinctiveness with its extinction probability (the evolutionarily distinct and globally endangered (EDGE) index, its developed form EDGE2, and parametric index \({}^{\alpha }\delta^{\prime}\)). We targeted 24 Diprotodontia species for conservation concern, with Mountain Pygmy Possum Burramys parvus and Koala Phascolarctos cinereus highlighted by all indices. We delimited eight key priority areas containing these target species, five of which were not covered by any protected areas. Further analyses of the potential impact of climate change-induced extreme events, together with stronger regulation of known local threats in light of local socioeconomic aspects seem to be urgent for the fate of evolutionarily distinctive Diprotodonts.