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Title: Nuclear and plastid DNA sequences reveal complex evolutionary patterns in Australian water-lilies (Nymphaea subgenus Anecphya, Nymphaeaceae)

item Wiersema, John

Submitted to: Australian Systematic Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/2008
Publication Date: 10/22/2008
Citation: Lohne, C., Borsch, T., Jacobs, S.W.L., Hellquist, C.B., Wiersema, J.H. 2008. Nuclear and plastid DNA sequences reveal complex reticulate patterns in Australian water-lilies (Nymphaea subgenus Anecphya, Nymphaeaceae). Australian Systematic Botany. 21(4):229-250.

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. The Australian water-lilies are perhaps the most beautiful of all, but have been little used in horticulture. This study was conducted to improve our understanding of the relationships among the Australian species, thereby permitting ornamental breeders to make better use of them. The results from our DNA studies agree with other observations in dividing them into two principal groups, one with smaller and one with larger seeds, and provide evidence of natural hybridization among them. Remarkably, a rare and unusual submersed aquatic plant found only in the remote Kimberley Region of Australia, which has always been placed in a genus of its own apart from water-lilies, is shown to be a member of the small-seeded group and is likely a highly specialized water-lily. These results will provide a more meaningful view of relationships, enabling water-lily breeders to make more successful crosses between related species.

Technical Abstract: This study represents the first comprehensive analysis of phylogenetic relationships within the Australian water-lilies, Nymphaea subg. Anecphya. Our 52-taxa dataset covers all species of the subgenus except the newly described N. alexii and includes information from the nuclear ITS as well as from the chloroplast trnT-trnF region. The results show that molecular data are consistent with morphology, because the subdivision of subg. Anecphya into two major clades, a large-seeded and a small-seeded group, could be confirmed. Within the large-seeded group, Nymphaea atrans and N. immutabilis seem to form one clade, whereas samples of N. gigantea, N. georginae, N. macrosperma and N. carpentariae form another. Relationships within the small-seeded group, containing all samples of N. violacea, N. elleniae and N. hastifolia, are less clear, since the trees obtained from the chloroplast and the nuclear marker are incongruent. The samples of N. violacea do not form a monophyletic group in each of the trees, but are paraphyletic with respect to those of N. elleniae, N. hastifolia and Ondinea. Polymorphisms among ITS paralogues, i.e. substitutions at single nucleotide positions and length polymorphisms, have been observed in some samples of N. violacea. This fact as well as the incongruent phylogenetic signal obtained from the chloroplast and the nuclear genomes point to recent hybridisation or introgression in this group. Remarkably, Ondinea purpurea is resolved within the small-seeded group by both markers and seems to have a close relationship to Nymphaea hastifolia.