蜡梅科中国特有群的遗传多样性及分子系统学

Calycanthaceae is a family of typical East Asia-North American.disjunctive distribution. In this family, Chimonanthus Lindl is an ancient endemic.genus in China. In Calycanthus, Calycanthus chinensis Cheng et S. Y. Chang is a.tertiary relic species in China and scatters in Zhejiang province. Calycanthus floridus.and Calycanthus occidentalis, the other two species in Calycanthus, distribute in the.east and west America, respectively. All the species are bushes and the most were.widely planted in garden and made into miniascapes as ornamental plant. Besides the.pharmaceutical value of plants in Chimonanthus was found in China 1000 years ago.and used extensively now. Because Calycanthaceae is a typical family of East.Asia-North American disjunctive distribution, the systematic and evolution problems.of the family were concerned by many scientists. In the Chimonanthus of the family.existed many natural populations in China and each species occupies special.distributing area itself respectively. Since the first species of the genus was published.in 1762, many species had been described. In 1965, three species were recognized in.this genus based on morphological and cytological characteristics: C. praecox (L.).Link, C. nitens Oliv, C. salicifolius S Y Hu., and some confusion was clarified (Nicely,.1965). During the 1980’s, many new species were published, including C..zhejiangensis M. C. Liu, C. grammatus M. C. Liu (Liu, 1984), C. campanulatus R. H..Chang et C. S. Ding and C. campanulatus var. guizhouensis R. H. Chang (Chang,.1980 and 1995) etc. The new species described since 1980 have stirred debate about.the taxonomy of this genus. Besides with man-made destruction recently, natural.range of Calycanthaceae was significantly reduced, and even the plant of Calycanthus.chinensis had become rare and endangered plants of second order by China. In order.to analysis the possible reasons that caused Calycanthus chinensis endangered and.propose genetic and evolutionary conservation strategies, and clear up the systematic.confusion of the family, this project was carried..In this project, the seeds and plantlets from the 20 natural populations were.collected, which were sowed and planted in a nursery of Huazhong Agricultural.University. Most of them grew very good..Leaf samples of 106 individuals from 11 populations were gathered and DNAs.were extracted from the leaf samples. Then the DNA samples were randomly.amplified with 25 arbitrary primers (RAPD) and 323 genetic loci were produced..Then the dendrograms were constructed from the standard genetic distances among.all the pairs of populations based on the unweighted pair-group average cluster of.STAT. The diagram tree suggested that the genus was identified as four species, viz..Ch. praecox, Ch. campanulatus, Ch. salicifolius and Ch.nitens, which was the same as.that from morphological analysis(see Ph. D. dissertation, topic: Biosystematics of.Chimonanthus, Ph D student: Chen Longqing, supervised by professor Chen Junyu)..Moreover the genetic relationship between Ch. praecox and Ch. campanulatus was.nearer, and that between Ch. salicifolius and Ch.nitens was nearer too. Besides, with.analysis of gene heterozygosity, proportion of polymorphic loci and genetic distance.within and among populations, the following conclusions were thus obtained: great.genetic variation from infra-population and the least variation from inter-populations.existed in Ch. praecox. Tendencies in Ch. salicifolius were similar to those in Ch..praecox, but slightly larger parts coming from inter-populations. In Ch. campanulatus,.the genetic variation of infra-population was the lowest, but that of inter-populations.was placed in the middle. That of Ch. nitens was the greatest both inter-populations.and infra-population. These results are meaningful for the effective conservation and.exploitation of these genetic resources. The geographic distribution areas of the 4.species were presented, and the speciation and evolutionary rel

收集蜡梅科中国特有类群的野生种质资源，利用RAPD分子标记技术，