Abstract
Scirpus hattorianus, a perennial sedge, was initially described as a Japanese species. Although this species has disappeared from Japan, recent works have treated it as conspecific with a common sedge in eastern North America. Herbarium studies and a search of the literature on Japanese S. hattorianus and the taxonomically confused naturalized species, S. georgianus, were performed to identify the origin of the former. Herbarium studies showed that Japanese S. hattorianus had been collected from only one, two, three, or four sites in a small area of Fukushima Prefecture between 1925 and 1939. The literature search revealed that a hydroelectric power plant had been built in the vicinity of the sites from which S. hattorianus had been collected, and that the materials for construction of the power plant had been purchased from a company located within the native distribution range of S. hattorianus in North America. This suggests the possibility that materials from North America were transported to the collection sites of S. hattorianus in Japan at that time, and that the plants may have been introduced accidentally with these imported materials. Accordingly, at present, it is deemed more appropriate to treat the Japanese S. hattorianus as a transiently naturalized sedge from North America rather than a native and extinct sedge.
