| Clintonia udensis Trautv. et Mey., a perennial herb, belongs to the genus Clintonia Raf. in the tribe Polygonateae (Liliaceae). Two ploid levels existed in this species (2n =14 and 4n =28), and its tetraploids were a kind of autopolyploidy. The distribution of the diploid C. udensis stretches from Northwest China's Yunnan Province to Russia's Primorskiy Kray, while the tetraploids are distributed in Yunnan, Himalayas, Japan, and a narrow area in Mt. Hualongshan of Southern Shaanxi. Due to the coexistence of two distinct cytotypes and the overlapping of their distribution areas, information on population structure and genetic variability is of great significance to the understanding of the polyploid origin, dispersal and evolution of C. udensis.In this thesis, efforts were made to reveal the evolutionary history of C. udensis and its polyploid origin from the aspects of both genetic diversity and molecular phylogeography. The results will provide supporting evidence for the further investigation into the spatial distribution pattern of C. udensis' genetic variation, its historical causes and dispersal, and references for the explanation of China's geological changes and post-Pleistocene geographical dispersal of plants.In this study, 15 ISSR primers were used to reveal the genetic diversity of 17 C. udensis populations. The results showed that the percentage of polymorphic bands on the populational level ranged from 11.90% to 59.52%, and that on the species level was 98.8%. Shannon's information index (0.6903) and gene differentiation index GST(0.6944) both indicated that there existed more genetic variation among populations than those within populations. AMOVA analysis revealed significant variation among populations (81.47% of the variance) and within populations (18.53% of the variance) (P < 0.003). The genetic distances among populations ranged from 0.0526 to 0.2777, with the average value 0.1220, which was higher than that among intraspecies populations (0.05). This also showed there was a significant genetic differentiation among populations. The gene flow among C. udensis populations (Nm=0.2200) was much lower than that of the cosmopolite species (Nm= 1.881). No significant statistical differences (analysis of molecular variance [AMOVA], P = 0.063) was detected between regions. The Mantel Test revealed no significant correlation between genetic distance and geographical distance (r = 0.299, P = 0.0633). The high level of genetic diversity was probably related with its wide geographical distribution and its evolutionary history;and the biological characteristics of this species, limited gene flow and genetic drift might account for the existence of relatively high inter-populational genetic variation.At the ploidy level, the level of genetic diversity of tetraploid populations approximately equaled that of the diploid populations (P: 32.94% and 24.08%;H: 0.1496 and 0.1161;/: 0.2127 and 0.1664, respectively). No significant differentiation (P — 0.3856) occurred between cytotypes. One possibility was that C. udensis tetraploids were autotetraploids that originated too recently to allow for the accumulation of mutations. A second possibility was that demographic forces associated with polyploid formation offset the forces that led to greater diversity.The atpB-rbcL noncoding spacer on cpDNA was sequenced from 17 C. udensis populations. It showed that the complete sequence of this noncoding spacer was 850bp. Totally, 38 mutational sites, including 10 parsimony informative sites and 28 singleton polymorphic sites, were detected, which accounted for 4.50% of all the analyzed sites. Both transition and transversion occurred in these mutational sites. The average number of nucleotide differences was 6.309. A total of 16 haplotypes were inferred from these polymorphic sites. Relatively high nucleotide diversity (Pi =0.00747) and haplotype diversity (H |
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