Submitted to: Taxon
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/23/2008
Publication Date: 11/26/2008
Citation: Lohne, C., Yoo, M., Borsch, T., Wiersema, J.H., Wilde, V., Bell, C.D., Barthlott, W., Soltis, D.E., Soltis, P.S. 2008. Biogeography of Nymphaeales: Extant patterns and historical events. Taxon 57(4):1123-1146. Interpretive Summary: Water-lilies are among the most beautiful of aquatic plants, usually forming the centerpiece of most aquatic gardens. These plants are also interesting to science in being the living descendents of one of the two most ancient lineages of flowering plants. Studies of these early flowering plants could tell us something about how the flower itself evolved and how environmental changes affected this process. Information from DNA and species ranges was analyzed in this study to predict how water-lilies and their relatives came to exist. Although the water-lily group is thought to have branched from the rest of the flowering plant tree over 130 million years ago, this analysis indicates that present-day water-lilies first appeared only around 60 million years ago, so any earlier ancestors of water-lilies are now all extinct. The oldest surviving groups of water-lilies likely arose in a vast northern super-continent under temperate conditions, but later, when the earth warmed, the younger tropical groups began to appear, spreading southward to other more isolated continents where today they make up the majority of species. This paper’s findings suggest that to study the most primitive flowers we will need to look much earlier than present-day water-lilies, but the information presented will still be helpful to paleontologists in interpreting and dating fossils of early flowering plants. It could also prove useful to scientists studying the impact of global climate change on the adaptive responses of plants.
Technical Abstract: This study is the first, comprehensive 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 Nymphaeales and all subgenera of the genus Nymphaea and sound phylogenetic hypotheses we estimate divergence times in Nymphaeales. Distribution data for all species is 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 analysis of extant biogeography showed that there are several centers of extant 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 super-continent was covered by tropical vegetation. The estimation of divergence times depicted two distinct radiation events, a rapid first differentiation into three major lineages during Palaeocene (Cabombaceae, Nuphar, remaining Nymphaeaceae) and the radiation of core Nymphaeaceae (Victoria, Euryale, Nymphaea incl. Ondinea) from Late Oligocene to Middle Miocene. Also the second radiation probably started in the Northern Hemisphere. Subsequent spatial separation and southward relocation of the descendants lead to the disjunct distribution of extant sister-lineages in core Nymphaeaceae, e.g. Euryale-Victoria or Nymphaea subgg. Hydrocallis-Lotos.