油松遗传结构与地理阻隔因素的相关性

油松(Pinus tabulaeformis)是我国特有广布树种。秦岭是我国亚热带和暖温带气候的重要分界线,贺兰山是我国西北干旱区与半干旱区的分界线。旨在以分布于秦岭、贺兰山和晋陕两省的10个天然油松种群为研究对象,通过对其线粒体DNA(nad1和matR内含子)的序列,探讨地理阻隔对油松遗传结构的影响。结果表明,10个天然油松种群的100个个体中共检测到27个单倍型,多态位点172个,简约信息位点35个,单一多态性位点137个。其中1个单倍型为全部种群共有,4个单倍型为2-5个种群共有,其余22个单倍型为各个种群所独有。在这10个种群中,有8个种群分别具有1-4个独有单倍型。尽管秦岭南侧种群和北侧种群分别具有两个和一个独有单倍型; 贺兰山东侧种群和西侧种群均具有3个独有单倍型;但是与晋陕种群(即油松分布区中心种群)相比,其种群独有单倍型平均数目则明显较少。与此同时,不仅秦岭南北两侧或贺兰山东西两侧种群的独有单倍型的进化关系往往较近,而且秦岭北侧或贺兰山东侧种群的独有单倍型与油松分布区中心种群的某些独有单倍型的关系亦较近。从而导致秦岭南北两侧或贺兰山东西两侧种群与油松分布区中心种群之间表现出比较复杂的聚类关系。由此可见,油松的遗传结构与山脉屏障的存在没有明显关系。

Analysis of relationship between genetic structure of Chinese Pine and mountain barriers

Chinese pine (Pinus tabulaeformis), an endemic to China, is the most widely distributed conifer in North China. The Qin Mountains are a major east-west mountain range in central China. This range spans about 1500 km from southern Gansu Province in the west to west Henan Province in the east. The highest peak rises to an elevation of 3,767 m above sea level. This range demarcates subtropical and warm temperate zones in China. The Helan Mountains are a mountain range forming the border of Inner Mongolia's Alxa League and Ningxia. It runs in the north-south direction with a length of about 200 km. The highest peak rises to an elevation of 3556 m above sea level. This range demarcates the arid and semi-arid regions in northwest China. To examine whether the mountain barriers have substantial effects on the genetic structure of Chinese pine, the mitochondrial DNA (nad1 and matR introns) sequence characteristics of 10 natural populations of this species from the Qin Mountains, Helan Mountains, and Shanxi and Shaanxi Provinces were studied. The results showed that a total of 27 haplotypes, 172 polymorphic sites, including 35 parsimony informative sites and 137 singleton variable sites were identified from 100 individuals of all 10 Chinese pine populations based on the sequences of two mitotypes. Of all the haplotypes (from h1 to h27), h1 was shared by all the populations; h3, h6, h9 and h27 were shared by 2-5 populations; and 22 other haplotypes were all unique ones. Eight of the 10 populations had one to four unique haplotypes. Although the populations in the north and south sides of the Qin Mountains (i.e. populations ZZ and NS) had one and two unique haplotypes, respectively; and both the populations in east and west sides of Helan Mountains (i.e. populations HLn and HLi) had three unique haplotypes; the average number of the unique haplotypes for them was smaller than that for the populations GD, LY, TY and HL (i.e. the populations in the central distribution area of Chinese pine). A mixed picture of the evolution relationship of the 27 mtDNA haplotypes was found. A close evolution relationship was detected between the unique haplotypes for the populations in the north and south sides of the Qin Mountains or for the populations in east and west sides of the Helan Mountains. There was a close evolution relationship between the unique haplotypes of the populations in the south side of the Qin Mountains or the east side of the Helan Mountains. Some of the unique haplotypes of the Shanxi-shaanxi populations were also detected. In addition, the results revealed that the genetic diversity in the species level was high, and the haplotype diversity and nucleotide diversity were 0.7120 and 0.0050 respectively. The analysis of molecular variance (AMOVA) showed that the percentage of variation within populations (90.16%) was higher than that among populations (9.84%). The genetic differentiation was significant (Fst = 0.0984, P < 0.01) among populations. Despite the mountainous barriers, the populations in the north and south sides of the Qin Mountains and in the east and west sides of the Helan Mountains showed a complicated classification relationship with the Shanxi-shaanxi populations. Therefore it was concluded that the genetic structure of Chinese pine was hardly associated with the mountainous barriers.