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Title: Phylogeny and biogeography of North-American wild rice (Zizania L.Poaceae)

item XU, XINWEI - Wuhan University
item Walters, Christina
item ANTOLIN, MICHAEL - Colorado State University
item ALEXANDER, MARA - Us Fish And Wildlife Service
item LUTZ, SUE - Smithsonian Institute
item GE, SONG - Chinese Academy Of Sciences
item WEN, JUN - Smithsonian Institute

Submitted to: Molecular Phylogenetics and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2009
Publication Date: 1/1/2010
Citation: Xu, X., Walters, C.T., Antolin, M.F., Alexander, M.L., Lutz, S., Ge, S., Wen, J. 2010. Phylogeny and biogeography of North-American wild rice (Zizania L.Poaceae). Molecular Phylogenetics and Evolution. 55:1008-1017.

Interpretive Summary: Problem: The evolution of the genus Zizania (North American wildrice) is unknown and this restricts our abilities to sample genetic diversity for germplasm banks. This aquatic/wetland genus is most closely related to Rhynchoryza, Zizaniopsis, and Luziola, which are New World species originating in South America. However, the occurrence of Zizania latifolia in Eastern Asia suggests an intercontinental disjunction in which geneflow typically migrates easterly from Asia to North America, with greater diversity in Asian taxa. Accomplishment: Through a study of polymorphisms in genetic markers, we show that Z. latifolia populations from East Asia have extremely low diversity, while Z. palustris, Z. aquatica and Z. texana populations from North America exhibit greater diversity. Based on this information, we inferred the biogeographic history of Zizania as a taxon that originated in North America and migrated westerly via the Bering land bridge into eastern Asia about 1.3 to 7 million years ago. We estimated the divergence times among the North American species to have occurred about 0.5 to 1.3 million years ago. Impact: Resolution of the evolution and diversification of Zizania within North America suggests that we should look for genetic diversity important for agricultural production (i.e., perennial growth habit) and nutrition (balanced complement of amino acids in grains) within the United States and Canada.

Technical Abstract: The wild-rice genus Zizania includes four species disjunctly distributed in eastern Asia and North America, with three species (Z. aquatica, Z. palustris, and Z. texana) in North America and one (Z. latifolia) in eastern Asia. The phylogeny and biogeography of Zizania were explored using sequences of seven DNA fragments (atpB-rbcL, matK, rps16, trnL-F, trnH-psbA, nad1, and Adh1a) from chloroplast, mitochondrial, and nuclear genomes. Zizania is shown to be monophyletic with two distinct clades each corresponding to eastern Asia and North America, respectively. The divergence between the intercontinental clades was dated to be 3.90 (95% HPD: 1.26-7.01) million years ago (mya) using the Bayesian dating method with the combined matK, trnL and nad1 data. The divergence time in the late Tertiary, together with the results of the dispersal-vicariance analyses and the phylogeographic structure of the eastern Asian Z. latifolia, favors a New World origin of Zizania and its migration into eastern Asia via the Bering land bridge. Among the three North American species, the plastid data and the haplotype network of the nuclear Adh1a gene suggest a close relationship between Z. palustris and the narrowly distributed endangered species Z. texana. Bayesian dating estimated the divergence of Z. aquatica from other North American Zizania to be 0.55 (95% HPD: 0.05-1.27) mya. Incomplete lineage sorting, and low frequent unidirectional introgression of Z. palustris into Z. aquatica best explain the non-monophyly of each of these two species.