TOWARD A REVISION OF THE GENUS ORTHOSIA (APOCYNACEAE: ASCLEPIADOIDEAE: ASCLEPIADEAE)

This paper summarizes the present knowledge of the genus Orthosia Decne., based on the study of herbarium material, type specimens, digital images, field observations, and Sanger sequencing of 101 accessions for six chloroplast markers. The results of these analyses encourage a rather narrow species circumscription in most cases. A total of 55 species are recognized, nine of which are new to science. Additionally, incomplete material from some remote areas points to the existence of a handful of yet undescribed species. For some species, morphological and molecular results are incongruent, also indicating the need for future studies. All accepted species are described and illustrated, and their distributions are provided. Nine species and two subspecies are newly described, 13 new combinations and two new synonyms are proposed, and 12 names are lectotypified and one is neotypified.