油松遗传结构与地理阻隔因素的相关性

Abstract

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 about200 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 Shanxishaanxi 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.