Two new Critically Endangered species of Ditassa (Apocynaceae) from the threatened cangas of the Iron Quadrangle, Minas Gerais, Brazil

Background and aims - Vegetation on ironstone outcrops is highly threatened, particularly due to the impact of mining. In this study, two new species of Ditassa (Metastelmatinae, Asclepiadoideae, Apocynaceae) from the cangas of the Iron Quadrangle (Minas Gerais, Brazil) are described and illustrated, and their conservation status is discussed. Material and methods - Species recognition is based on a morphological and molecular study of recent and historical collections, including a survey of the main herbaria of Brazil, Europe and the United States. Conservation status assessments are based on the evaluation of areas of occupancy and the impact of iron mining in the region. Key results - The two new species are morphologically similar to species in the "Hemipogon from the Espinhaço" clade, which includes Morilloa. Nevertheless, they exhibit flowers with a double corona and are described in Ditassa here, following preliminary phylogenetic analyses with 73 plastid-coding regions. These species are known from only two highly disturbed locations each and are Critically Endangered. A key to identify the 14 species of Metastelmatinae currently recorded in cangas of the Iron Quadrangle is provided. Conclusion - The Critically Endangered Ditassa cangae and D. ferricola are examples of poorly known, nearly extinct species under strong anthropogenic pressure caused by intense mining activities and the lack of adequate legislation for the protection of canga landscapes.