Taxonomy of Vincetoxicum s.str. (Asclepiadoideae, Apocynaceae) from southern Asia including three new species and resurrected names

This paper presents a taxonomic study of genus Vincetoxicum s.str. from southern Asia. Eleven regional endemic species are recognized on the basis of herbarium studies and fieldwork. Three new species are described: V. lenifoliumsp. nov. (endemic to Pakistan), V. stewartianumsp. nov. (endemic to India), and V. subcanescenssp. nov. (endemic to Pakistan, Kashmir and Tibet). Three species names, V. cabulicum, V. glaucum and V. kenouriense, previously treated as synonyms of V. glaucum, V. canescens and V. hirundinaria, respectively, are resurrected. A neotype is designated for the Afghani endemic V. cabulicum. A lectotype is chosen from the syntypes of V. glaucum. We resolve the long-standing taxonomic problems in three species complexes: V. arnottianum, V. luridum, V. sakesarense, and V. stocksii; V. glaucum, V. canescens and V. cabulicum; and V. hirundinaria and V. kenouriense. Geo-taxonomic distinctions of southern Asian taxa are highlighted by excluding from henceforth the long misrecognized western Eurasian taxa V. canescens and V. hirundinaria. Furthermore, a detailed account of the genus including illustrations of whole plants, leaves and corona, distribution maps, a taxonomic key, morphological descriptions, synonymy, notes, and information on phenology, distribution and habitats is provided. Finally, provisional conservation assessments are provided, which indicate that V. cardiostephanum and V. sakesarense are critically endangered.