Two new species of Parnassia (Celastraceae) from karst cave and Danxia landform in Southwest China

Two new species of Parnassia found in mountainous areas of Chongqing City, Southwest China, are described and illustrated: P. zhengyuanum M.X. Ren & J. Zhang and P. simianshanensis M.X. Ren, J. Zhang & Z.Y. Liu respectively. Parnassia zhengyuanum is found in a limestone cave near Mt. Jinfo, Nanchuan District, Chongqing City. This tiny plant has special spoon-shaped leaves and undivided staminodes with green apices. Parnassia simianshanensis was discovered in Mt. Simian, Jiangjin County, Chongqing City. This species grows along streams on red sandstones, i.e. in Danxia landform. It can be easily distinguished by its unique rhombic leaves and the five- or four-branched staminodes. The conservation status of P. zhengyuanum and P. simianshanensis are assessed respectively as ‘Critically Endangered’ (CR) and ‘VU’ (Vulnerable) according to IUCN criteria. The roles of karst and Danxia landforms in the speciation process are discussed.