XVI International Botanical Congess

A well-corroborated phylogeny of water lily genera recently has been achieved based on agreement between non-molecular data and DNA sequences obtained from both organellar and nuclear genomes. These data sets clarify the limits of the order Nymphaeales to comprise two clades, the Nymphaeaceae (Barclaya, Euryale, Nuphar, Nymphaea, Ondinea, Victoria) and Cabombaceae (Cabomba and Brasenia), the latter monophyletic family representing the closest known sister group to the extant water lilies. When floral fetures were evaluated the pleiomerous condition often cited as an example of the unspecialized (primitive) angiosperm condition revealed several instances of secondary increases (e.g. Victoria). It remains uncertain whether the Cabombaceae, having few perianth and essential parts, are reduced from a more complex pleiomerous flower or that all nymphaeaceous flowers acquired their pleiomery by secondary increases. Findings from a comparative study of floral ontogeny in Nymphaeales and Nelumbonales are presented that expand our perspective of evolutionary trends in these taxa.