朱鹮种群谱系构建及遗传多样性研究

【作者】 石张燕；

【导师】 蒙世杰；

【作者基本信息】 西北大学 ， 动物学， 2003， 硕士

【摘要】 朱鹮(Nipponia nippon)是亚洲东部特有的—种涉禽，由于近代人类经济活动加剧而濒临灭绝。1981年在我国陕西省洋县发现的7只朱鹮是当时已知的世界上仅存的野生朱鹮个体。为保护这—濒危鸟类，我国学者对朱鹮展开了多方位的研究。然而迄今为止，这些研究主要限于生态学、形态学等方面，分子生物学领域则很少涉及。近年来朱鹮种群频繁出现诸如残疾幼鸟增多、成鸟繁殖力下降等问题，已严重影响到种群的生存与发展，因此，从分子水平对朱鹮进行研究，了解其基因信息和遗传多样性，并确定个体之间的亲缘关系，从而制定科学、合理的繁殖计划与保护对策，已成为当务之急。 随机扩增多态性DNA(Random　Amplified　Polymorphic　DNA，RAPD)技术是—种DNA分析的常用方法，其原理是采用一系列碱基顺序随机排列的引物对所研究物种的DNA进行PCR扩增。虽然任何一条引物检测DNA的位点是有限的，但采用大量引物则可使检测区域覆盖整个基因组。由于RAPD技术具有简便、迅速且无须了解研究对象的分子信息等优点，因而广泛应用于系统树构建、遗传多样性研究等众多的领域。 我们采用RAPD技术对来自洋县的32只朱鹮和来自北京动物园的5只朱鹮进行了研究，根据实验数据计算了任意两个个体之间的相似性系数和遗传距离，分别用UPGMA法和简约法构建出其谱系关系，并对种群的遗传多样性作了初步的探讨。我们在对Operon公司OPG系列和OPA系列引物进行优化筛选的基础上，用24条随机引物共扩增出163条谱带，即检测了朱鹮基因组中的163个位点，其中23条引物的扩增结果具有多态性；谱带的多态比率最小为0，最大为85.71％，平均为48.99％；在由37只朱鹮组成的种群中，任意两个个体之间的遗传距离绝大多数在0.1以下。这些结果表明，目前朱鹮个体间的相似程度很高，种群的遗传多样性水平较低。我们认为这一现象是由朱鹮历史上曾经历过瓶颈效应，基因库大大缩小和长期的频繁近交而造成的。一定程度的遗传变异性是维持种群的适应力与进化潜力的必要条件，为使朱鹮免于灭绝的厄运，必须避免其种群遗传多样性的进一步丧失，并尽可能增加个体间的基因交流，最大限度地避免近亲繁殖。由于在朱鹮保护的初期阶段未能对离巢幼鸟进行环志，故现存朱鹮的谱系关系混乱，给人工选种配对带来了困难；我们所构建的谱系图可以在一定程度上应用到西北大学硕士学位论文沐潭鸟保护的实际工作中，为合理地制定繁殖考。根据谱系而在繁殖酉己付时尽可能地避免近交，将增进个体间的基因交流，使种群的遗传多样性得以维持，并有可能提高其生存能力与进化潜力，最终达到更好地保护这一稀世珍禽的目的。更多还原

【Abstract】 Crested ibis(Nipponia Nippori),a kind of peculiar wading bird in east Asians facing its extinction because of humanbeings’ economic activities.Seven crested ibises found at Yong county Shaanxi Province in 1981 were the all wild individuals left in the world then.To protect this rare bird,scholars have carried out a great deal of researches on it in many areas.However,till now, studies is mainly confined to some areas such as ecology and morphology, little was done in the area of molecular biology.Phenomina such as disable individuals increasing and adults’ producing ability decreasing occurred more frequent in recent years.These badly affected the existence and development of this species.So,getting the information about crested ibis’ gene and genetic diversity through studies at molecular level and setting up scientific producing and protecting projections are becoming urgent tasks.Randomly amplified polymorphic DNA(RAPD) is a common method to analyze DNA,and is based on PCR using a series of primers made up of randomly arranged basesAlthough the sites detected by a single primer are limited,the entire genome can be inspected when many primers were used. Because of the method is convenient and fast, and no molecular information about the species to be studied is needed, RAPD is widely used in many areas such as study of phylogenetic tree and genetic diversity.We studied 32 crested ibises from Yong county and 5 crested ibises from Beijing Zoo by RAPD. Similarity coefficient and genetic distances between two arbitrary individuals were caculated according to the data of experiments,the pedigree was constructed by two means(They were UPGMA and parsimony),and genetic diversity was discussedBased on selecting the best conditions of PCR with OPG and OPA primers from Operon company,we obtained 163 bands using 24 random primers.In other words,163 sites in crested ibis’ genome were detected.The bands from 23 primers showed polymorphism.Minimurn of polymorphic ratio was 0,maximum was 85.71%,and average was 48.99%.In the population which was composed by 37 individuals, most of genetic distances between two arbitrary individuals were less than 0.1.The results showed that the degree of similarity among crested ibises was high while genetic diversity in thepopulation was low accordingly. We think this situation should be owed to bottleneck effect and a rather frequency of inbreeding. It is necessary for a species’ adaptation and evolutionary potential to keep genetic variety at a relative level. Genetic diversity in the population must not be lost furthermore and gene exchange among individuals should be enhanced as much as possible to avoid extinction of crested ibis. At the same time,close breeding should be strictly avoided,too. Because callow birds had not be marked with rings in the early period of protection, the pedigree was confused. So,it is very difficult to carry out artificial pairing. For its reference value to set reasonable breeding plan, the pedigree chart constructed by us can be applied in the protection to crested ibis.According to a good breeding project, inbreeding can be avoided and gene exchange can be increased. That means genetic diversity in crested ibises can be sustained, and on the base the populations’ adaptive capacity and evolutionary potential should be promoted. In this way,the rare bird will be protected more successfully.更多还原