PJB-2017-649
PHYLOGENY OF RHEUM (POLYGONACEAE) BASED ON CPDNA TRNS-G SEQUENCES
Ailan Wang
Abstract
The genus Rheum (polygonaceae) is mainly confined to the Qinghai-Tibetan Plateau (QTP) and adjacent areas. It is a good example of the extensive diversification common to temperate genera of the QTP. To test the monophyly of the genus and evaluate intrageneric relationships, a total of 27 individuals, belonging to seven of eight sections of Rheum L. (only excluding Sect. Orbiccularia), were collected in the QTP and adjacent areas. Molecular phylogenic trees were reconstructed based on cpDNA trnS-G sequences. The total alignment of trnS-G sequences was 953-1041 bp in length, and 1153bp after refinement by hand. Results of phylogeny show that the monophyletic origin of Sect. Rheum is supported, while another six sections (Sections Palmata, Acuminata, Deserticola, Spiciformia, Globulosa and Nobilia) were found to be of paraphyletic origin in the parsimonious trees. Rh. alexandrae and Rh. nobile, the only two species in Sect. Nobilia, were unrelated according to molecular phylogenetic analysis. The phylogenic relationship of the monophyletic species Rh. globulosum of Sect. Globulosa needs further study. The status of Sect. Orbiccularia could not be evaluated. In conclusion, the phylogeny of Rheum based on cpDNA trnS-G sequences may serve as a reference for studying rapid speciation and convergent evolution in arid habitats.
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