New insights into character evolution, hybridization and diversity of Indian Nymphaea (Nymphaeaceae): evidence from molecular and morphological data

A comprehensive reassessment of Indian Nymphaea (Nymphaeaceae) based on morphology, RAPD and nucleotide sequence data of the ITS, trnK intron, matK and rbcL gene was conducted. Although considerable morphological variations have been reported, pollen colour and rhizome shape are two characters which have not been mentioned in previous studies. The transformation from yellow to white coloured pollen may have evolved independently and is probably associated with a strong selective pressure acted upon by the animal pollinators on white pollen of N. pubescens and N. rubra. Rhizome shape could easily discriminate among subgenera; the difference in shape (triangular, globular and cylindrical) probably highlights the success in their distribution. Our studies using RAPD revealed high genetic variability among individuals of N. caerulea. This may be attributed to the breeding system followed, which could be an outcrossing species. But the lack of genetic diversity in N. tetragona is probably due to founder events, whereby a solitary founder individual from China could have resulted in the establishment of this single population of approximate to 2530 individuals with no detectable variations. Molecular cloning of the ITS region of N. rubra, necessitated by the presence of additional signals in the sequencing chromatogram, confirmed the origin of this plant taxon through hybridization involving N. lotus and N. pubescens as the parental species.