A new endemic species of Sesuvium (Aizoaceae: Sesuvioideae) from the Caribbean Basin, with further notes on the genus composition in the West Indies

A distinctive new species, Sesuvium curassavicum Sukhor. (Aizoaceae: Sesuvioideae), restricted to the Caribbean Basin (Kingdom of the Netherlands: Curaçao and Bonaire Islands, North Colombia: La Guajira Department, and North Venezuela: Falcón State), is described and illustrated. It differs from all other perennial species growing in the West Indies by its papillate stems and wrinkled seeds. Based on the molecular phylogenetic analysis of nrDNA (ITS) and three plastid regions (rps16 gene intron, atpB-rbcL and trnL-trnF intergenic spacers), S. curassavicum is included in the ‘American’ clade, but its relationships are not fully resolved. The samples of the plants known as S. microphyllum fall within the ‘Sesuvium portulacastrum’ clade, and for that reason this species is considered here as a synonym of S. portulacastrum being an ecological form of the latter species. Sesuvium revolutifolium, S. ortegae and S. revolutum, described from cultivated plants are established as earlier synonyms of S. verrucosum, for which S. revolutifolium has priority and is proposed here as the correct name. These three species names seem to share the same provenance which cannot be Cuba, as stated in the protologue for S. revolutifolium, but rather Mexico. The name Sesuvium sessile is discussed and merged with S. portulacastrum. A new diagnostic key to the Sesuvium species in the West Indies is provided. In total, we accept for the West Indies the following species: S. curassavicum, S. humifusum, S. maritimum, S. portulacastrum and S. rubriflorum. The origins of collections of the neotype of Radiana petiolata and the holotypes of Sesuvium microphyllum and S. spathulatum are clarified.