【作者】 毛璐茜；

【导师】 计翔；

【作者基本信息】 南京师范大学 ， 生态学， 2011， 硕士

【摘要】 舟山眼镜蛇分布于我国南部(包括台湾、香港及海南地区)及越南北部地区,30年前它曾是中国最常见的蛇类之一,由于当地居民的过度捕猎现已被列为濒危物种。为了检测舟山眼镜蛇的遗传多样性、种群结构和进化史,本研究在其分布的全境范围内系统采样,分析来自27个种群390条个体的线粒体控制区序列。结果显示,在全长1029 bp中存在40个变异位点,共检测到52个单元型。NJ树显示52个单元型分为两支：来自四川米易、云南河口的H41自成一支；来自除米易之外的其他各种群的其余51个单元型聚为一支。罗霄山脉和南岭山脉是限制舟山眼镜蛇基因交流的重要屏障。以这两个山系为界,把舟山眼镜蛇分为东部、南部和西部三个集合种群。东部种群单元型主要集中在单元型网络图的右侧,其中H1为多个种群所共享,包括南方种群；西部种群主要集中在网络图的左侧,其中H30和H42为多个种群所共享。南部种群主要位于网络图的中间连接位置。AMOVA分析结果显示,32.58%的变异发生在地区之间,地区内种群间变异占43.18%,种群内变异占24.25%。中性检验和歧点分布分析提示东部集合种群显示历史上曾经历种口扩张,τ值为1.992,其种群种口扩张约发生在0.298百万年前。本研究还从舟山眼镜蛇基因库中筛选出13个AC重复类型的多态性微卫星位点。这13个位点从永安和赣州两个种群的48条个体中筛选而来,各位点等位基因数在4-12之间,平均值为7.54,观测杂合度0.213-0.854,平均值为0.459,期望杂合度0.301-0.838,平均值为0.6341,有较高的杂合度,其中四个位点偏离哈温平衡。这些通过微卫星位点显示出来的高水平的多态性将有助于进一步深入研究舟山眼镜蛇的基因流动、种群结构及进化史。更多还原

【Abstract】 The Chinese cobra (Naja atra) is an oviparous elapid snake with a distribution covering southeastern China (including Taiwan, Hongkong and Hainan) and northern Vietnam. The cobra was one of the most commonly found snakes in China some thirty years ago. Largely because the cobra has been over hunted by local people for meat, skin, medicine and handiwork, it is currently regarded as a highly vulnerable species according to a published volume of China Red Data Book of Endangered Animals. To assess the genetic diversity within N. atra, and its population structure and evolutionary history, we sequenced 1029 bp of control region for 390 individuals collected from 27 localities covering almost the whole range of the snake. Forty variable sites were observed, and 52 haplotypes were defined. We identified two genetically distinct clades. one clade including haplotypes from Hekou and Miyi (western China), and the other clade from the whole distributional range except for Miyi.The Luoxiao mountain ranges and Nanling mountain ranges are important barriers limiting gene exchange between populations on the both sides of these two mountain series. Analysis of molecular variance indicated that a significant proportion (32.58%) of the total variation in the mitochondrial DNA data could be attributable to differences among groups:[Eastern China] [Southern China & Vietnam] [Western China]. A significant proportion of variation also occurred among populations within groups (43.18%) and within populations (24.25%). One plausible scenario to explain ourgenetic data is a historically widespread population that has been structured by vicariant factors such as the mountains and sea level fluctuations. Significantly large negative values of Fu’s Fs test reject the null hypothesis of neutral evolution of the control region marker for the population group in Eastern China. This provides an inference for population expansion in Eastern China, which is supported by the mismatch distribution analysis and Rogers test of sudden population expansion. The value ofτfor the population group in Eastern China was 1.992. For the substitution rate for a variety of snakes were about 0.0065 site-1 myr-1, the expansion time was estimated to be 0.298 mya.We characterize thirteen polymorphic microsatellite loci isolated from N. atra genomic libraries, which enriched for AC-motif microsatellites. The thirteen loci were screened on a group of 48 individuals from two populations, one in Yong’an and the other in Ganzhou. These markers revealed a relatively high degree of genetic diversity (4-12 alleles per locus) and heterozygosity (Ho ranged from 0.213-0.854 and He ranged from 0.301-0.838). Four loci deviated from Hardy-Weinberg equilibrium. The high level of polymorphism revealed by these microsatellite markers will be useful for the study of gene flow, population structure and evolutionary history of N. atra.更多还原