Taxonomic Revision of Oxalis subsect. Oxalis (Oxalidaceae)

The classification of Oxalis subsect. Oxalis (Oxalidaceae) is revised based on phylogenetic, cytological and morphological evidence. For the flora of Japan, one new species and one new variety are described, and five new combinations are proposed. The new species, O. nipponica, resembles O. griffithii, but is distinguished by its unique phylogeny, larger genome and distribution. Oxalis nipponica is subdivided into two subspecies, nipponica and kantoensis based on phylogeny and fruit length. Subsp. kantoensis is further divided into two varieties based on ploidy level, length of the fruit and seeds and habitat. While diploids correspond to var. kantoensis, the tetraploids correspond to the newly described var. alpigena. Variety alpigena resembles O. acetosella and has been confused with it. Fourteen taxa, including one hybrid, are recognized in subsect. Oxalis.