【作者】 沈栋伟；

【导师】 陈小勇；

【作者基本信息】 华东师范大学 ， 生态学， 2007， 硕士

【摘要】 近年来，人们逐渐认识到植物基因型多样性能够控制群落结构和生态系统过程。在类似海草之类物种多样性较低的生态系统内，基因型多样性取代物种多样性发生作用。在崇明东滩，物种组成简单，入侵种互花米草（Spartina alterniflora）是当地的优势种之一，其基因型多样性可能作用于植物的入侵能力。本文以入侵植物互花米草为研究对象，采用分子标记手段和野外控制实验，调查互花米草种群的遗传多样性，分析不同基因型多样性的情况下互花米草的入侵扩散能力，以期揭示基因型多样性与生态系统功能的相互关系，并为互花米草的防治工作提供科学依据。利用6对引物对16个米草种群进行微卫星分析，共获得38个等位基因。种群平均等位基因数为6.333，Shannon遗传多样性指数为0.703，种内遗传多样性指数（Hs）为0.42，种间遗传多样性(D_ST)为0.200，总遗传多样性（H_T）为0.620。说明总体上互花米草种群的变异程度比较高，而且大部分来源于种群内。但种群间也有分化，基因分化指数(G_ST)为0.322，基因流（Nm）为0.49，说明各个种群间存在地理隔离。不同互花米草种群，遗传多样性指数，相差比较大。美国南卡罗来纳州（FB）和崇明（CM）种群遗传多样性最高，罗源（LY）、江苏盐城（SY）和江苏启东（QD）次之，上海金山（JS）、厦门海沧（HC）、潍坊（WF）和日照（RZ）则种群遗传多样性最低。这说明福建罗源和江苏是互花米草进入中国的一个重要站点。种群的遗传距离平均值为0.478，其中距离最大的为广东茂名（GD）和温岭永安（WE）种群（1.462）；最小的是东海农场（DH）和温州永强（LQ）种群（0.031）。同样的，遗传一致度平均为0.653，最大值出现东海农场（DH）和温州永强（LQ）种群（0.969），最小值出现在广东茂名与温岭永安（WL）种群（0.232）。聚类分析得到潍坊小渚河（WF）、日照（RZ）种群与其它14个种群的遗传距离较大，成为一个独立的分支，为大米草。对崇明东滩22丛的基因结构进行研究，发现丛间的遗传多态性为100％，而丛内为0，说明在崇明低潮滩，互花米草丛间大部分都是由不同克隆系分株发展而成，而丛内克隆组成单一，为同一个克隆系分株。利用这一特点，进行控制实验研究不同基因型多样性与物种入侵能力为主要指标的生态系统功能之间的关系。在单种样方中，我们发现不同基因型间可能存在平均单粒重和种子数之间的不同结实策略的选择。对不同基因型多样性进行分析，我们发现在株数、扩散面积和平均单粒重上，基因型多样性有促进互花米草入侵能力的可能。株数和种子平均单粒重中，三基因型处理具有明显的“超产”现象，说明交互作用可能发生在不同基因型之间，但基因型多样性作用的实现则需要过程。更多还原

【Abstract】 Recently, people found that plant genotypic diversity could pedict community structure and govern processes of an ecosystem. It may functionally replace of the roles of species diversity in species-poor ecosystems, such as seagrass. The invasive plant Spartina altermflora is one of dominant species in Dongtan of Chongming, so the its genotypic diversity may have community-or ecosystem-level consequences.We investigated the genetic diversity of the populations of Spartina altermflora, and studied the invasive ability of different genotypic diversity, then revealed the relationship between the genotypic diversity and ecosystem function by SSR and a field experiment.Sixteen populations and 477 individuals were sampled and genotyped to reveal the genetic structure. We detected a total of 38 different SSR alleles by 6 primers. At population level, mean number of alleles per loci was 6.333, Shannon diversity index was 0.703, the genetic diversity within populations （Hs） was 0.420, genetic diversity among populations (D_ST) was 0.200, and total genetic diversity （H_T） 0.620. Most of genetic diversity was within populations. But there is also the differentiation among populations. Nei’s gene diversity coefficient （Gst） was 0.322, with gene flow （Nm） of 0.491, indicating geographical isolation between the populations.Genetic diversity indexes between populations were different largely. South Carolina of USA （FB） and Chongming of Shanghai （CM） had the highest diversity, followed by Luoyuan of Fujian Province （LY）, Yancheng （SY）, and Qidong （QD） of Jiangsu Province. Jinshan of Shanghai （JS）, Haicang of Xiamen （HC）, Weifang（WF）, and Rizhao of Shandong Province （RZ） had the lowest diversity. The results were coincided with the introduction route in which Luoyuan of Fujian Province and Jiangsu Province were locations that S. alterniflora was first introduced. The genetic distance of populations ranged from 0.031 to 1.462, and the average was 0.478. The genetic identity was from 0.232 to 0.969, and the average was 0.653. We concluded the populations of Weifang （WF） and Rizhao （RZ） were Spartina anglica.We studied the 22 clusters of Spartina alterniflora in Chongmin and found there were different clones among clusters, but same within cluster. Using a field experiment, we tested the relationship between the genotypic diversity and plant invasive ability. We found high number of seed output of genotype D, but its single seed weight is much lower than other genotypes. There was a trend that genotypic diversity increased the invasive ability including of the number of root,dispersal area and single seed weight. "Overyielding" occurred in three-genotype treatment. But there were no statistical differences among different treatments. Thus, above results suggested genotypic diversity might enhance the invasive ability of Spartina alternijlora.更多还原