【作者】 李朝阳；

【导师】 陈良碧； 李菁；

【作者基本信息】 湖南师范大学 ， 生物化学与分子生物学， 2006， 硕士

【摘要】 尖叶拟船叶藓（Dolichomitriopsis diversiformis（Mitt．）Nog．）是船叶藓科（Lembophyllaceae）拟船叶藓属中的中国唯一一种植物，对研究拟船叶藓属的系统演化与属间亲缘关系有重要的意义。近几十年来，由于环境污染及生态破坏的日趋加剧，该植物所受到的胁迫越来越严重，分布范围也越来越狭窄，分布区域渐成“岛状”，从而成为我国苔藓植物遭受威胁最严重的类群之一。因此，尖叶拟船叶藓濒危机制和保护策略的研究亟待进行。本研究以贵州梵净山为主要研究地，以RAPD为主要分子标记，ITS序列分析和同工酶分析为辅助标记，探讨了拟船叶藓属（Dolichomitriopsis）和猫尾藓属（Isothecium）属间的鉴别和亲缘关系，研究了尖叶拟船叶藓居群间和居群内的遗传多样性及居群的遗传结构，并对尖叶拟船叶藓濒危的机制进行了探讨。初步研究结果如下：1．野外踏查发现，尖叶拟船叶藓的生态环境比较独特单一，呈片段化，绝大部分尖叶拟船叶藓种群都附生于树干上，少见土生或石生。2．拟船叶藓属和猫尾藓属是船叶藓科中亲缘关系较近的两个属，外形上很相似，野外调查易混淆。通过RAPD扩增和ITS测序，以RAPD标记为主，辅以ITS序列分析，能将两个属很好的区分开来，并能准确的鉴别这两个属的物种。同时，RAPD标记也表明尖叶拟船叶藓居群间有较高的遗传多样性，并且这种多样性与其地理位置无明显相关性，可能受其小生境的影响较大。3．RAPD分析表明，尖叶拟船叶藓物种水平的多态性位点百分率（PPB）为87.76％。居群水平的遗传变异程度较低，多态性位点百分率（PPB）为20.52％。每个位点的平均有效等位基因数（A_E）为1.1456。居群水平的基因多样度(H_Epop)为0.0813，物种水平的基因多样度(H_Esp)为0.2223，遗传分化系数(G_st)为0.6329。在总的变异中有63.29％的变异来源于居群间，有36.71％的变异存在于居群内，表明尖叶拟船叶藓居群分化十分明显。数据分析结果说明了尖叶拟船叶藓物种水平的遗传多样性较高，但居群水平的遗传多样性则较低，而且其遗传多样性受小生境的影响较大。其中遗传漂变和环境与基因互作导致的适应性变异可能是影响居群分化的主要原因。4．过氧化物同工酶分析结果表明，尖叶拟船叶藓物种水平有较高的遗传多样性，并且受小生境的影响较大，居群间有明显的分化。5．尖叶拟船叶藓濒危的因素推测有二：一是独特的栖息环境以及生活环境的片段化；二是尖叶拟船叶藓为雌雄异株种，有明显的雌性偏向，有性繁殖率低，孢子数量少，孢子体败育率低，以无性繁殖为主的繁育特性等导致的种群退化和环境适应性减弱。对于尖叶拟船叶藓的保护，应以就地保护为主，保护其赖以栖息的生活环境，特别是贵州的梵净山，使之不致减少以致灭绝，以迁地保护为辅，以扩大其种群分布范围。更多还原

【Abstract】 Dolichomitriopsis diversiformis （Mitt.）Nog. is the unique species of Dolichomitriopsis, Lembophyllaceae in China. It is very important to the systematic evolution and identification of relationships of Dolichomitriopsis. Recently, D. diversiformis occur a much more narrow distribution, and islandization, because of environment pollution and ecology degradation. It is believed that D. diversiformis is one of the endangerous moss species. Base on these, endangerous mechanism and protective strategy of them came into being a serious problem.In our research, the relationship between Dolichomitriopsis and Isothecium, the inter- and inner-population genetic diversity and hereditary architechure and the endangerous mechanism of D. diversiformis was investigated, by using RAPD and major molecular marker, ITS analysis and isoenzymes analysis as auxiliary factors. Preliminary results showed as follows.（1） In ecological investigation, the environment of D. diversiformis occurs phenomenon of fragmentation and specialization. Almost all populations grew on the surface of the tree stems, and land- or rock-attached types did not occur.（2） Polichomitriopsis is near to Isothecium in family of Lembophyllaceae on genetic relationship. Because of similarity on appearance, they are obscure in the field investigation. Based on the RAPD amplification and ITS sequence, the two species in two different genus can be identified. The RAPD results also tell us, inter-population genetic diversity of diversiformis was so high, and the diversity is related to the mini-environment and has litter relationship with geographic site.（3） Polymorphism site percent of D. diversiformis is 87.76%. Variation on population level is very low, the polymorphism site percent of population is 20.52%. Number of average effective alliles （A_E） of each site is 1.1456. Gene diversity (H_Epop) of population level is 0.0813, and it of species is 0.2223, G_st is 0.6329. 63.29% of all the alternations comes from inter-population, others comes from inner-population.（4） Results of isoenzymes also suggested the high genetic diversity and that is effected by the mini-environment. Otherwise, the differentiation of population was developed.（5） Endangerous factors of D. diversfformis should be two. First, habitat distinctivity and fragmentation cause species endanger. Second, the characteristic of asexual reproduction is the prominent result in D. diversiformis population degeneration. Base on these determination, the protective strategy should be mainly protect the living environment of D. diversiformis, especially the Fanjin Mount in GuiZhou Province, and change residence auxiliary to enlarge the distribution.更多还原