Prioritizing the orchids of a biodiversity hotspot for conservation based on phylogenetic history and extinction risk

With limited resources for curtailing the escalating biodiversity crisis, a rational means of setting priorities among threatened species is of pre-eminent concern. Combining phylogenetic history and conservation status to estimate the evolutionary distinctiveness that would be lost in the event of a given species becoming extinct has gained momentum in analyses of animal taxa, but has not previously been attempted for plants. Focusing on the heavily impacted Indo-Burma Biodiversity Hotspot, we examine the utility of various phylogenetic metrics in prioritizing members of Orchidaceae, the largest family in the eco-region. Reconstructing a time-calibrated phylogenetic tree for 592 of the known 2170 species in the region reveals Thailand, South China and Vietnam as the areas harbouring the highest phylogenetic diversity and Tropidia curculigoides, Thaia saprophytica and Risleya atropurpurea as accounting for disproportionately great evolutionary distinctiveness. Although patchy, integrating global and national Red List data justifies several priorities, particularly in the intensively poached genera Paphiopedilum and Dendrobium. Addressing biases in the phylogenetic and conservation status data sets requires that botanical gardens in the region accession under-represented taxa and that citizen scientists and professional researchers contribute more fully to Red Lists. Governments are urged to step-up protection of habitats highlighted as cradles of exceptional orchid diversity.