Papers published in 2007 have shed new light on relationships within the waterlily family. The first two papers are:

Perhaps the most startling discovery suggests that Ondinea is related to Nymphaea subgenus Anecphya. The image below of apetalous Ondinia purpurea subsp. purpurea may LOOK unlikely to be placed within subgenus Ancephya but Ondinea purpurea subsp. petaloidea, with four petals, could be the "missing link".

These chloroplast DNA studies clearly place the enigmatic N. petersiana within the Lotos group. Its leaves certainly look like a night bloomer, but its blue day-opening flowers have placed it in Nymphaea subgenus Brachyceras until now. The morphology might suggest that it could be the result of an ancient hybridization between these two groups and evidence from nuclear DNA could aid in evaluating this hypothesis.

N. petersiana being collected in Malawi >
Chrissie Chawanje Photo

Hybridization between these two subgenera, belonging to different major tropical clades of the waterlily genus (the apocarpous [Brachyceras-Anecphya] and the syncarpous [Hydrocallis-Lotos] clades would be an exceedingly improbable phenomenon in comparison to Brachyceras-Anecphya hybridization, which is far more probable given the close relationship between the two subgenera.

The new studies definitely show N. lotus and N. pubescens as separate species. Some taxonomists have kept them separate "largely for historical reasons" but their independence as species is now confirmed.

Other than the clear relationships between the subgenera of Nymphaea as indicated, and that between Anecphya and Ondinea, there are no other phylogenetic conclusions that can be drawn from these papers, although the relationship between Euryale-Victoria and the Nymphaea subgenera is worthy of further study. So too is the relationship of Nuphar vs. Cabomba-Brasenia to the remaining Nymphaeales.

In another interesting development, Hydatellaceae, a family of small submerged and emergent aquatic plants found in Australia, New Zealand and India, have been moved from the order Poales to Nymphaeales. See these papers: