Biogeography of Nymphaeales: extant patterns and historical events

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Abstract
With the present study we attempt to elucidate the history of the order Nymphaeales—water‐lilies and relatives—in time and space. On the basis of a dense taxon sampling that covers all genera of Cabombaceae and Nymphaeaceae and all subgenera of the genus Nymphaea , and on the basis of well‐supported phylogenetic hypotheses, we estimate divergence times in Nymphaeales. Distribution data for all species are used to reconstruct ancestral ranges and to identify possible dispersal events in the biogeographic history of Nymphaeales. Considering the fossil record for the clade as well as geologic history, a plausible historical scenario can be drawn. The assessment of extant biogeography shows that there are several centres of species diversity for Nymphaeales, i.e., northern South America, Central America, the Zambezian region of Africa and northern Australia. However, the diversification of the Nymphaeales started in the Northern Hemisphere when the northern landmasses were covered by tropical vegetation, except for the very high latitudes. The estimation of divergence times depicted two distinct radiation events, a rapid first differentiation into three major lineages during the Paleocene (Cabombaceae, Nuphar , remaining Nymphaeaceae) and the radiation of core Nymphaeaceae ( Victoria , Euryale , Nymphaea incl. Ondinea ) from the Late Oligocene to Middle Miocene. The second radiation probably started in the Northern Hemisphere. We hypothesize that subsequent spatial separation and southward relocation of the descendants led to the disjunct distribution of extant sister lineages in core Nymphaeaceae, e.g., Euryale‐Victoria or Nymphaea subgg. Hydrocallis and Lotos .

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