Youngia thunbergiana (Crepidinae, Cichorieae, Asteraceae), a Species Overlooked in the North American Flora

Youngia thunbergiana is documented for North America from Alabama, Georgia, Maryland, Virginia, and South Carolina. Lloyd Shinners in 1964 reported this species for the District of Columbia and North Carolina, a fact apparently overlooked by subsequent investigators. When recognized, this taxon was generally treated as Youngia japonica subsp. elstonii, based on specimens from Hawaii, in accordance with the monograph of Youngia by Babcock and Stebbins (1937). Subsequently, when not accorded taxonomic recognition, it has been regarded as a synonym of the Y. japonica polymorphic complex. Shinners presented evidence for recognition at specific rank and, as such, asserted that Y. thunbergiana is its correct name. The present research is in agreement with his findings of Shinners. Youngia pseudosenecio is another name subsequently proposed within the Y. japonica complex that has been synonymized with Y. japonica subsp. elstonii. Nuclear ITS sequence data lend support to Y. pseudosenecio and Y. thunbergiana being the same species and that this entity represents a lineage distinct from Y. japonica.