祁连山区特有物种黑虎耳草的居群遗传多样性研究

利用叶绿体基因(rbcL和trnS-G)及核糖体DNA内转录间隔区(ITS),对祁连山区狭域分布的特有物种黑虎耳草8个居群(115个个体)进行遗传多样性研究,旨在揭示黑虎耳草的居群遗传结构及其历史进化过程。结果表明:(1)所有取样个体共检测到4个cpDNA单倍型和9个ITS单倍型,其中祁连山东南部的居群固定较多的单倍型和特有单倍型,而西北部居群只固定少数几个广泛分布的单倍型,且遗传多样性普遍较低。(2)基于cpDNA数据和ITS数据的分子变异分析(AMOVA)显示,遗传变异主要来源于居群内。(3)基于cpDNA数据的中性检验表明,Tajima’s D(-1.012 30,P> 0.05)和Fu&Li’s D*(-2.066 77,P> 0.05)均为负值,均不显著;歧点分布分析结果显示,黑虎耳草居群经历过近期的扩张事件。根据物种现有遗传分布格局推测,黑虎耳草在第四纪冰期时退缩到祁连山东南部的边缘避难所,间冰期或冰期后回迁到祁连山西北部地区,在回迁过程中由于奠基者效应导致祁连山西北部的居群仅固定少数广泛分布的单倍型,并呈现出较低的遗传多样性;由于居群较小且相互隔离,该...

Population Genetic Analysis of a Qilian Mountains Endemic Species Saxifraga atrata (Saxifragaceae)

Chloroplast DNA fragments (rbcL, trnS G) and nuclear ribosomal DNA internal transcribed spacer (ITS) were employed for studing population genetic diversity of Saxifraga atrata, which has a narrow distribution range endemic to the Qilian Mountains. The aim was to reveal genetic structure and population historical evolution of S. atrata. The results showed that: (1) four cpDNA and nine ITS haplotypes were isolated among the 115 individuals. Populations from the southeast edge of the Qilian Mountains showed high haplotype richness and uniqueness, whereas northwest populations only harbored a few widespread haplotypes and usually showed low levels of genetic diversity. (2) Analysis of molecular variance (AMOVA) based on both cpDNA and ITS datasets showed that most variations were from within populations. (3) Neutrality tests based on cpDNA dataset exhibited negative values, but not significant. However, mismatch distribution analysis strongly supported a recent expansion of S. atrata. According to extant genetic structure, we speculated that S. atrata retreated to the southeastern refugia of the Qilian Mountains during the Quaternary. The northwest populations were the result of recolonization during inter glacial or post glacial periods. Founder effect associated with recolonization should be responsible for haplotype impoverishment and low levels of genetic diversity of northwest populations. Bottleneck effect and genetic drift might be much severe in this narrow endemic species due to small population size and fragmentation, resulting in extremely low levels of total genetic diversity and average within population diversity compared with other Saxifraga species widespread in the Qinghai Tibet Plateau and Himalayas.