Commelina obliqua Buch. - Ham. ex D. Don (Don 1825

Commelina obliqua Buch.-Ham. ex D.Don Commelina obliqua Buch.-Ham. ex D.Don (Don 1825: 45), nom. illeg., non C. obliqua Vahl. – Heterocarpus obliquus Hassk. (Hasskarl 1870: 7). Syn. nov. Accepted species Commelina paludosa Blume. Remarks Commelina obliqua Buch.-Ham. ex D.Don represents a posterior homonym to C. obliqua Vahl and is thus illegitimate. This name also seems to represent the source of the historical association of C. obliqua Vahl with the taxon correctly named C. robusta. The Palaeotropical C. obliqua Buch.-Ham. ex D.Don (= C. paludosa) is indeed a member of the C. robusta group and very similar to C. scabrata. Alternatively, C. obliqua Vahl actually represents the correct name for the Neotropical taxon that has so far been treated as C. rufipes var. glabrata (see Remarks for C. obliqua Vahl). Regarding the correct author of Heterocarpus obliquus, since C. obliqua Buch.-Ham. ex D.Don is illegitimate, and illegitimate names cannot be combined (Turland et al. 2018: Art. 6.10). Thus, H. obliquus represents a replacement name (i.e., a new name) for this taxon under Heterocarpus, with the correct author citation being “Hassk.”.