【作者】 马佳梅；

【导师】 殷寿华；

【作者基本信息】 中国科学院研究生院（西双版纳热带植物园） ， 植物学， 2008， 硕士

【摘要】 流苏石斛(Dendrobium fimbriatum)属于兰科(Orchidaceae)石斛属(Dendrobium),具有重要的观赏价值和药用价值。由于其自身生物学特性及人为破坏,导致其野外居群大量减少。本文采用ISSR分子标记对西双版纳境内的5个流苏石斛居群进行了遗传多样性和遗传结构分析,为流苏石斛的保护提供科学依据。利用12条引物对5个自然居群的114个个体进行了扩增,共产生出117条条带,其中105条为多态性条带。分析结果表明,流苏石斛居群水平遗传多样性较低。在物种水平上,流苏石斛多态位点百分率PPB为89.74%、Nei’s基因多样性指数H为0.3227,Shannon’s多样性信息指数Hsp为0.4779;在居群水平上,各个居群的多态位点百分率PPB差异较大(6.84-39.32%),平均值为23.93%,Nei’s基因多样性指数H为0.0871,各个居群的Shannon’s多样性信息指数Ho平均为0.1290。AMOVA分析的结果显示,流苏石斛的遗传变异大多数存在于居群间,占总遗传变异的74.79%,而居群内的遗传变异仅占25.21%。基于Nei’s遗传多样性分析得出的居群间遗传分化系数Gst=0.7443;Shannon’s居群分化系数为0.7470;各居群间的Nei’s遗传一致度(I),其范围为0.5882-0.8331。Mantel检测发现,居群间的遗传距离和地理距离之间不存在显著的正相关关系(r = 0.2419,P = 0.2416)。居群间基因流Nm=0.1810,基因流较小,可能跟西双版纳复杂的地形或者传粉昆虫的近距离传播以及种子萌发特性有关。鉴于流苏石斛居群内较低的遗传多样性水平和居群间较高的遗传分化,应该对流苏石斛各居群的所有个体实施及时的就地保护,促进种群自然更新。在建立迁地保护居群时,尽可能从所有居群中,根据自然居群的遗传结构取样,防止栽培种群的遗传均质化,促进基因交流。同时,应及时将迁地保护区的幼苗回归到野外居群中,以补充野外居群。更多还原

【Abstract】 Dendrobium fimbriatum (Orchidaceae) is an endemic and endangered species in China. It can be used as ornamental and medicinal plant.The biological charaters of the species, habitat fragmentation, especially rubber planting, have caused decline of population size of the species. ISSR were used to investigate the genetic diversity and genetic structure of five natural populations (114 individuals) of the species, in order to put forward scientific conservation strategy.For five natural populations, twelve primers of ISSR produced a total of 117 unambiguous and repetitious bands, of which 105 (89.74%) were polymorphic. The results showed that Dendrobium fimbriatum exhibited a comparatively low genetic diversity: at species level, the value of the average percentage of polymorphic bands (PPB) was 89.74%, expected heterozygosity (H) was 0.3227, Shannon’s Information index (Hsp) was 0.4779; at population level, the value of the average percentage of polymorphic bands PPB was 23.93%,expected heterozygosity H was 0.0871,Shannon’s Information index Ho was 0.1290. Most of genetic variation partitioned among populations (74.79%). Genetic differentiation among populations had a high degree: the coefficient of gene differentiation among populations Gst was 0.7443. Pairwise genetic identity (I) values among populations ranged from 0.5882 to 0.8331. No correlation was found between geographical and genetic distance, which indicated gene flow may be influenced by complicated local landform or insect pollination and animal-madiated seed dispersal. On the basis of ISSR marker analyses, recent habitat fragmentation may have led to the loss of genetic diversity or genetic differentiation in the endangered species.Based on the above findings, we propose that conservation management of Dendrobium fimbriatum shoud include protection of natural habitats occupied by all five wild populations and preservation of germplasm in botanical gardens from multiple seed sources. More populations should be selected whenever ex situ or in situ conservation strategies are taken.更多还原