2022 Volume 97 Issue 6 Pages 313-322
The taxonomic status of Isachne subglobosa Hatus. & T.Koyama (Poaceae: Micrairoideae), described from the southern Ryukyu Archipelago, is re-examined. This species was originally described as being closely related to I. globosa (Thunb.) Kuntze, which is widely distributed in temperate regions throughout tropical Asia and Australasia, but was often considered a synonym of I. dispar Trin., or has been treated as an insufficiently known taxon. Our field study and re-examination of the type materials revealed I. subglobosa to be distinct from I. dispar (= I. pulchella Roth), but it was difficult to distinguish from I. globosa (spikelet size, leaf width and hairiness were often variable even within the same population at the type locality). Type materials of I. globosa var. effusa (Trimen ex Hook.f.) Senaratna from Sri Lanka, which has morphological characteristics similar to I. subglobosa, were also considered to fall within the variation range of I. globosa. In conclusion, we consider I. subglobosa to be a synonym of the widespread and variable I. globosa, as well as I. globosa var. effusa. The lectotype of I.australis R.Br. var. effusa Trimen ex Hook.f. is designated.
