Incorporating evolutionary history into conservation assessments of a highly threatened group of species, South African Dioscorea (Dioscoreaceae)

Abstract

In an era of increasing threat most species of plant still lack an assessment of extinction risk or an understanding of priority for conservation. Evolutionary distinctiveness (ED) has been used in conjunction with extinction risk to prioritise species for conservation. We apply this approach to an economically important group of plants in Africa; South African Dioscorea (yams), focusing on the Africa clade that contains species used mainly medicinally with a distinct evolutionary history. The results of IUCN Red List assessments for these species were used in subsequent EDGE (Evolutionary Distinct and Globally Endangered) analysis. Species distribution models were produced for Africa clade species using MaxEnt, which were then combined together with the EDGE scores to produce species richness (SR), extinction risk (ER), ED and EDGE diversity maps. Five out of the 15 South African Dioscorea species (all nested in the Africa clade) were found to be in a Red List threat category, and this category was shown to be the main determinant of its EDGE ranking. The spatial distribution of SR, ER, ED and EDGE were compared, and we use these maps to prioritise important areas for conservation in South Africa with hotspots identified as priorities for future conservation of Africa clade Dioscorea.