Pontederia cordata L., Sp. Pl. 1: 288. 1753.

Pellegrini, Marco O. O., Horn, Charles N. & Almeida, Rafael F., 2018, Total evidence phylogeny of Pontederiaceae (Commelinales) sheds light on the necessity of its recircumscription and synopsis of Pontederia L., PhytoKeys 108, pp. 25-83 : 25

5.1. Pontederia cordata L., Sp. Pl. 1: 288. 1753.

Unisema cordata (L.) Farw., Pap. Michigan Acad. Sci. 3: 91. 1924.

Narukila cordata (L.) Nieuwl., Amer. Midl. Naturalist 3: 101. 1913. Lectotype (designated by Reveal et al. 1987). UNITED STATES. Virginia and Maryland, fl., fr., s.dat., P. Kalm s.n. (LINN barcode LINN-HL407-4).

Pontederia lancifolia Muhl., Cat. Pl. Amer. Sept.: 34. 1813.

Unisema cordata fo. lancifolia (Muhl.) Farw., Pap. Michigan Acad. Sci. 3: 92. 1924.

Narukila cordata var. lancifolia (Muhl.) Nieuwl., Repert. Spec. Nov. Regni Veg. 12: 101. 1913.

Pontederia cordata var. lancifolia (Muhl.) Torr., Fl. N. Middle United States: 343. 1824. Lectotype (designated by Lowden 1973). UNITED STATES. Carolina, fl., fr., s.dat., G.H.E. Muhlenberg 242 (PH barcode PH00033652!).

Distribution.

Widely distributed in North, Central and South America from Canada to Uruguay and the West Indies.

Taxonomical notes.

Pontederia cordata has always been the origin of much debate and taxonomical confusion in the genus. Most of the species currently accepted by us in Pontederia s.l. have either been confused or compared with P. cordata , at some point. This can be demonstrated by how many of them have been treated either as synonyms or infraspecific taxa by different authors ( Fernald 1950; Lowden 1973; Godfrey & Wooten 1979; Novelo & Lot 1994). Pontederia cordata is morphologically and phylogenetically related to P. lancifolia , with only weak differences related to leaf morphology, thus should not be recognised taxonomically. Otherwise, we believe that, based on the current phylogenetic and morphological data, P. cordata , P. ovalis , P. parviflora and P. sagittata should be treated at the species level, until further studies can properly deal with the problem.