Nymphaea nouchali var. caerulea

Nymphaea nouchali var. caerulea, is a water lily in the genus Nymphaea, a botanical variety of Nymphaea nouchali. It is an aquatic plant of freshwater lakes, pools and rivers, naturally found throughout most of the eastern half of Africa, as well as parts of southern Arabia, but has also been spread to other regions as an ornamental plant. It was grown by the Ancient Egyptian civilization, and had significance in their religion. It can tolerate the roots being in anoxic mud in nutritionally poor conditions, and can become a dominant plant in deeper water in such habitats. It is associated with a species of snail, which is one of the main hosts of the pathogen causing human schistosomiasis. The underwater rhizomes are edible. Like other species in the genus, the plant contains the psychoactive alkaloid aporphine (not to be confused with apomorphine, a metabolic product of aporphine). Nymphaea spectabilis, a purple form known from cultivation, and N. capensis, found throughout eastern, central and southern Africa, as well as a number of other named taxa, were synonymised to N. nouchali var. caerulea in the 1989 addition to the Flora of Tropical East Africa (FTEA) series, a position which has generally been accepted, although some of the authorities in Bangladesh and in the United States disagree. In 2012 there was a phylogenetic study where N. caerulea was more related to N. gracilis, an endemic of northern Mexico, than it was to N. nouchali. The evolutionary tree was a consensus of ITS2 and matk. According to this study, N. caerulea should not be considered as a variety of N. nouchali. When genomes from the water lily genus (Nymphaea) were published in the journal Nature in 2020, N. caerulea was cited under that name, not as N. nouchali var. caerulea. Another phylogenetic study from 2021 found N. caerulea (as N. capensis) to be closest related to N. colorata, an east African species. Nymphaea nouchali is itself a taxonomically challenging species, with a distribution that spans Australia, throughout southern Asia, across Africa to the Western Cape.