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资助项目
GST, P < 0.05) were exhibited by this species. The SAMOVA revealed seven diverging groups of related chlorotypes, six of them had distinct nonoverlapping geographical ranges: one in the northeast comprising 10 populations, a second with a southeast distribution comprising 22 populations, and the remaning four groups comprising 15 populations located in the west part of the species’ range along different river valleys. The genetic clustering of populations into three regions was also supported by analysis of molecular variance, which showed that most genetic variation (82.43%) was found among these three regions. Two clusters were distinguished by both phylogenetic analysis and genealogical analysis of chlorotypes, one consisting of chlorotypes from the western region and the second consisting of those from the eastern region. Significant genetic differences between the two regions might be attributed to vicariance and restricted gene flow, and this vicariance could be explained by the physical environmental heterogeneity on each side of the Tanaka-Kaiyong Line. Following the uplift of the Tibetan Plateau, the reorganization of the major river drainages was primarily caused by river separation and capture events. These historical events could change the distribution of S. davidii from fragmented to continuous (Upper/Lower Jinshajiang and Yalongjiang/Daduhe), and from continuous to fragmented (Nujiang and Jinshajiang/Honghe). However, spatial and temporal patterns of phylogeographic divergence are strongly associated with historical disjunction rather than modern drainage connections. Moreover, the following north-south split in the eastern region and effective isolation with their genetic diversity were essentially modelled by genetic drift. The higher chlorotype richness and genetic divergence for populations in western region compared with other two regions suggests that there were multipe refugia or in situ survival of S. davidii in the Himalayan-Hengduan Mountain region. Fixation of chlorotypes in the northeastern region and near fixation in the southeastern region suggest a recent colonization of these areas. We further found that this species underwent past range expansion around 37-303 thousand years ago (kya). The southeastern populations likely experienced a demographic expansion via unidirectional gene flow along rivers, while northeastern populations underwent a more northward expansion, both from initial populations (s) (21, 22, 23) preserved on eastern refugia (Jinshajiang). This process might have been accompanied with a series of founder effects or bottlenecks making populations genetically impoverished. 3. Phylogeographic analysisbased on nuclear sequence，We sequenced the nuclear (ncpGS) region in all populations sampled, recovering 23 nuclear haplotypes. Compared to cpDNA, both NST (0.470) and GST (0.338) were relatively lower, but NST was also significantly larger than GST. 37.10% of the total variation was distributed among regions which was much lower than that shown by chlorotypes. Thus, more extensive distribution of nuclear haplotypes was exhibited across the geographical range instead of the strong population subdivision observed in chlorotypes. Similarly to the chloroplast data, we found that genetic differentiation of nDNA was positively correlated with the geographical distance, but the increase in the geographical distance between populations did not increase the genetic differentiation of nDNA as rapidly as that of cpDNA. These contrasting levels between the chloroplast and nuclear genomes of S. davidii are likely due to limited gene flow of cpDNA by seeds vs. the extensive gene flow of nDNA by wind-mediated pollen in the population history. We also determined from nuclear markers that haplotype diversity was reduced in the southeastern and northeastern regions due to the loss of rare haplotypes in western region. This reduction of gene diversity is also a signature of founder events or recent bottleneck during post-glacial colonization. However, nuclear diversity within populations remains high. This provides evidence that regionally pollen flow might be sufficiently high to blur the genetic identity of founder populations over a reasonably large spatial scale.3. Relationships among three varieties，The phylogenetic analysis identified two phylogroups of chlorotypes, corresponding to S. davidii var. davidii and var. chuansinesis. The former was distinguished by the abscence of predonminant nuclear haplotype H1 of the latter. The monophyletic group of chlorotypes in var. davidii and var. liangshanesis showed their relatively close relationship. And their genetic divergence from the third variety appears to be relative to their slight morphological difference in leaf size and the divergent environmental niche spaces they occupy. Thus, the observed differences in morphological characters between var. chuansinesis and other two varieties can be explained by the seed dispersal limitation illustrated above (as inferred by geographical separation) and by environmental heterogeneity (as inferred by precipitation or elevation) or by a combination of both. After all, the geological changes, drainage reorganization, and floristic differences following the Himalayan uplift have been suggested to affect the genetic structure of S. davidii. These results provide new insights into the phylogeographic pattern of plants in China. In addition, the unique population genetic structure found in S. davidii has provided important insights into the evolutionary history of this species. The genetic profile uncovered in this study is also critical for its conservation management. Our study has uncovered the existence of at least two ‘evolutionary significant units’ independent units within S. davidii, corresponding to var. davidii from eastern region and var. chuansinensis from western region. The conservation efforts should first focus on most western populations and on the southeastern ones exhibiting high levels of genetic diversity, while the genetically homogeneous northeastern populations located in the degraded Loess Plateau should require much greater conservation 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pingbianensis J. L. Huang & X. Z. Liu, is a newly described perennial herb narrowly distributed in South-east Yunnan, China. It belongs to genera Tupistra Ker Gawler(Liliaceae). It usually occurs on outcrops of bare rock, or occasionally as an epiphyte on tree trunks covered with humus and moss. T. pingbianensis is unusual in that it exhibits rarity according to three different ways of measuring rarity, i.e. it has a small geographical range, is a habitat specialist, and always has low abundance where it occurs. Because of this, T. pingbianensis has been listed as an endangered species and catalogued in the Chinese Species Red List. In order to discuss the causes of rarity of T. pingbianensis, the multidisciplinary investigations of the seed and seedling establishment, cytology, breeding system, and population genetic structure of the endangered T. pingbianensis were performed in this thesis. Besides, the corresponding conservation strategies were also proposed according to the above-mentioned. The main results are summarized as follows:1. Biological traits of T. pingbianensis,T. pingbianensis is a perennial herbaceous with a creeping rhizome, thick basal leaves, and an inflorescence that is a terminal spike. Florescence is from November to December, while fruiting occurs between November and December in the next year. Reproduction and spread also occurs clonally via rhizomes, most seeds simply fall from the mother plant and germinate where they land. It occurs on outcrops of bare rock, or occasionally as an epiphyte on tree trunks covered with humus and moss, which are naturally rare habitat. Throughout its small geographical range, T. pingbianensis occurs as discrete, small populations size. 2. Seed germination traits of T. pingbianensis,Seed morphology was observed and effects of substrates soil types, light, sowing depth on germination percentage of the species T. pingbianensis were investigated primarily. The results showed that the average seed size was (1.17±0.02) cm × (0.79±0.01) cm × (0.77±0.01) cm (length × width × thickness), per-hundred-seed-weight was about 35.03±0.12g. Among the three different substrates soil types and sowing depths, seeds of T. pingbianensis germinate best in alkalescence soil and shallow sowing depth (2cm). It could germinate in the both light and dark, but the germination rate can be accelerated by light obviously. Its seed has high germination rate not just in greenhouse, but also in the field. We considered that this is a good strategy to expand its population in the special habit.3. Karyotype evolution status of T. pingbianensis,The karyotype of total eight species in Campylandra, Tupistra and Aspidistra from China were reported. Considering Tupistra has the similar morphological character with Campylandra but resemble Aspidistra in karyotype. The results support the earlier study that Tupistra is a transition between Compylandra and Aspidistra. Besides, our results also showes that the T. pingbianensis and T. fungilliformis has higher karyotype asymmetry than other species in this genera, which means these species have higher karyotype evolution status. 4. Reproduction ecology of T. pingbianensis, The flower phenology, pollinators of T. pingbianensis were documented herein. We also examined the breeding system of T. pingbianensis and seed fitness traits to determine what forms of pollination and mating occur in this naturally rare species, and is there evidence of inbreeding depression in its populations. The results shows that the flowers opened 10-15 days, which suggest stigma and pollen can keep high vitality for a long time (10-15 days). The only pollinators observed on T. pingbianensis flowers were ants (Aphaenogaster smythiesii Forel,Formicidea), springtail (Hypogastrura sp., Hypogastruridae, Collembola) and one species of beetles (Anomala corpulenta Motsch, Rutelidae). These pollinators generally have restricted movement capacities and hence promote geitonogamy or mating between individuals in close proximity within populations. The results of out crossing index (OCI) pollination experiments in our study suggest that T. pingbianensis has an animal-pollinated, mixed selfing and outcrossing breeding systems. However, a pollination experiment also fail to detect significant inbreeding depression upon F1 fruit set, seed weight and germinate rate fitness-traits. Since naturally rare species T. pingbianensis is not seriously genetically impoverished and likely to have adapted to tolerating a high level of inbreeding early in its history. 5. Conservation genetic of T. pingbianensis, The levels and partitioning of genetic diversity were investigated in Tupistra pingbianensis. Here genetic diversity and patterns of genetic variation within and among 11 populations were analyzed using AFLP markers with 97 individuals across its whole geographical range. High levels of genetic variation were revealed both at the species level (P99 = 96.012%; Ht = 0.302) and at the population level (P99 = 51.41%; Hs = 0.224). Strong genetic differentiation among populations was also detected (FST = 0.2961; ⍬Ⅱ= 0.281), which corresponded to results reported for typical animal-pollinated, mixed selfing and outcrossing plant species. Special habitat and its life history traits may play an important role in shaping the genetic diversity and the genetic structure of this species. Based on the special habitat in T. pingbianensis, the most suitable strategy for its conservation is the protection of its habitat. Moreover, given the observed strong genetic differentiation among populations of T. pingbianensis, the preservation of genetic diversity in this species will require the protection of many populations as possible to maintain the current levels of genetic 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