KIB OpenIR  > 昆明植物所硕博研究生毕业学位论文
Thesis Advisor张长芹
Degree Grantor中国科学院研究生院
Degree Discipline植物学
Abstract椴树科(Tliaceae)滇桐(Craigia yunnanensis)是经济价值和系统学意义均较突出的乔木树种。本文对滇桐的居群结构特征和更新方式,传粉生物学特性和繁育系统,不同居群间的种子和幼苗相关性状指标及种子萌发特性,遗传多样性等方面进行了综合研究,旨在探讨滇桐的致濒因子,为滇桐的保护和利用提供依据。主要研究结果如下:通过三年的资源调查,仅在云南东南部文山地区和西南部德宏地区找到六个野生滇桐居群。到2007年,六个居群健存的生殖植株数为584株,另外还有大量的幼苗和萌生枝。径级结构分析表明滇桐具有实生苗更新和萌生更新两种更新方式,从幼苗成长为幼树有障碍。幼龄树和成年树的个体径级结构多为间歇型,这与人为干扰等有关。当前,种植草果对滇桐栖息地的侵占和树木砍伐是两个严重威胁滇桐居群生存的因素。对文山州西畴县法斗分布区片断化生境中的滇桐开花物候、传粉生物学特性观察和繁育系统实验研究表明:滇桐每个花序有2-9朵两性花,单花花期为3-4天;单个花序花期为5-14天;同株异花授粉可以结实,但结实率低;杂交指数(OCI)大于4,花粉-胚珠比(P/O)等于1381;有效传粉昆虫为大头丽蝇(Chrysomyia megacephala),该种的繁育系统属于异交为主,部分自交亲和,传粉过程需要传粉者。在自然条件下滇桐结籽率较小(6.26±0.75%)可能与传粉昆虫少等因素有关。对六个野生滇桐居群的11个适合度相关性状指标比较研究,同时检测了居群大小与这些性状指标的相关性。结果表明:六个研究居群在测量的11个性状指标上存在显著差异(P < 0.05)。相关分析表明,除单个果实中的种子数(P < 0.01)外,其余性状指标的居群均值与居群大小之间均无显著相关性;各项性状指标与地理气候因子之间无显著相关性(P > 0.05),各性状指标之间在进行Bonferroni矫正后也无显著相关性。来自法斗和江东居群的种子,在12小时光照条件下的种子萌发率显著高于连续黑暗条件下的种子萌发率(W-FD: P < 0.01, W-JD: P < 0.05)。采用AFLP分子标记对滇桐六个居群共105个成年个体的遗传多样性检测表明,滇桐在物种水平上的遗传多样性虽然不低(PPL = 69.19%),但居群内的遗传多样性却较低(居群平均:PPL = 26.22%)。文山地区居群的遗传多样性(PPL = 52.43%)高于德宏地区居群(PPL = 34.05%),其遗传分化程度也较大(Nei’s GST = 0.575; FST = 0.655)。UPGMA聚类分析将文山地区的四个居群聚成一支,而德宏地区的两个居群聚成一支。Mantel 检测表明地理距离和遗传距离间有显著相关性(P < 0.05)。相关分析表明,居群隔离指数与居群内的遗传多样性之间均呈显著的负相关关系(P < 0.05)。
Funding ProjectCraigia yunnanensis W. W. Smith & W. E. Evans (Tiliaceae) is an endangered deciduous tree species which has high scientific and economic value. C. yunnanensis is seriously threatened and has been pushed to the verge of extinction due to vegetation destruction in China and consequent contraction of its distribution. Hence, it was listed as a nationally rare and endangered plant in 1999 and has also been proposed as a second-ranked plant for national protection in China and included in IUCN red list. As a scientifically important and valued tree species with endangered status, the wild populations of C. yunnanensis therefore represent is a genetic resource that must be conserved. To provide basic information for its conservation, the population dynamics and population size structures, pollination biology and breeding system, eleven fitness-related characters and the genetic variability based on AFLP were comprehensively studied. The main results are summarized as follows: A total of six wild populations of C. yunnanensis were found in two disjunct regions of Yunnan, i.e. WenShan (SE Yunnan) and DeHong (SW Yunnan), from 2005 to 2007. Additionally, in all but one of the populations we detected, mature trees were felled between 2005 and 2007, so destruction of most of these populations is ongoing. Across the six populations of extant C. yunnanensis found during our study, the total number of mature (reproductive) individuals detected was 584 in 2007,plus larger numbers of seedling and resprouts from cut trunks. The result of surveying Population structure showed that there are two regeneration types which are seedlings and sprouts. Seedlings occurred abundantly in gaps or open areas and the size class frequency distributions were often discontinuous, and the same general pattern occurred in all the investigated populations for juveniles and adults. The numbers of seed-origin individuals did however decline sharply with increasing size, indicating a high mortality rate going from seedling to sapling stage may be a problem for this species. Additionally, the cash crop cultivation and logging seriously threaten the survival of the species. We conducted field observations and artificial pollination experiments on the floral biology, pollination process and breeding system of Craigia yunnanensis in Fadou, Xichou county of Yunnan province. The lifespan of a single hermaphrodite flower is approximately 3-4 days. A cyme has 2-9 flowered. The flowering period of an inflorescence is usually 5-14 days. The flowers of C. yunnanensis were protandrous. The stamens were within petal-like staminodes in the opening flowers until the flower withered. Without touchment, the bractlike staminodes can’t open. Self-pollination was partially avoided by temporal and spatial isolation of male and female organs within the same flower. However, autogamous and geitonogamous pollination is unavoidable because of the large number of flowers on a single tree and the action of pollinators. The values of both OCI (≥4) and P/O (1381) and the results of bagging tests indicated there was no apomixes in C. yunnanensis and the breeding system of the species was outcrossing with partial self-compatibility and the pollinators were required during the pollination process. The most frequent effective floral visitor was only beautiful fly (Chrysomyia megacephala). Fruit set and seed set in natural condition were 56.67±3.85% and 6.26±0.75%, respectively. Therefore, lack of pollinators, low pollination efficiency, unavoidable geitonogamous pollination and partial self-compatibility and inbreeding in small populations may account for the low fruit set, especially seed set.Variations in seed traits, seed germination, and seedling growth characters among six Craigia yunnanensis populations were evaluated. All seed and seedling traits exhibited significant differences among populations (P < 0.05). The fitness of seed as assessed by seed size, seed germination and seedling trait was independent of population size, except for the number of seeds per capsule (r = 0.93,P < 0.01). Correlations between geo-climatic variables of seed origin and seed and seedling related characters were insignificant (P > 0.05). For some populations, germination capacity in 12-h photoperiod was significantly higher than that in completed darkness(W-FD: P < 0.01, W-JD: P < 0.05).Genetic variation within and among six populations was assessed using AFLP markers. Genetic diversity was higher at species level (PPL = 69.19%, HE = 0.221) than at population level (PPL = 26.22%, HE = 0.095, Is =0.140), and populations in southeast Yunnan were strongly differentiated from those in southwest Yunnan (Nei’s GST = 0.575; FST = 0.655). UPGMA analysis demonstrated a clear genetic division between the two populations from DeHong (SW Yunnan; D-JD and D-HG) and the four from WenShan (SE Yunnan; W-FD, W-LH, W-ML, and W-MG). Within-population genetic variation was significantly correlated with population isolation (r(PPL) = -0.94, P = 0.006; r(HE) = -0.85, P = 0.032; r(Is) = -0.87, P = 0.025), but not with population size (r(PPL) = 0.63, P = 0.178; r(HE) = 0.54, P = 0.268; r(Is) = 0.56, P = 0.249).
Document Type学位论文
Recommended Citation
GB/T 7714
高则睿. 濒危植物滇桐的保护生物学研究[D]. 中国科学院研究生院,2010.
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