Independent origins of Spiranthes ×kapnosperia (Orchidaceae) and their nomenclatural implications

Spiranthes Rich. (Orchidaceae) is a commonly encountered but systematically and nomenclaturally challenging component of the North American orchid flora. Here, the evolutionary history and hybrid origin of the recently described S. sheviakii Hough and Young are critically examined. The available molecular data unambiguously support a hybrid origin of S. cernua (L.) Rich. × S. ochroleuca (Rydb.) Rydb. for S. sheviakii, the same parentage as the priority name S. × kapnosperia M.C. Pace. As hybrid formulas can have only one correct name, S. sheviakii is a synonym of S. × kapnosperia. It is likely that S. × kapnosperia evolved independently at least twice in at least two widely disjunct locations.