基于线粒体DNA控制区的新疆北鲵种群遗传多样性分析

Analysis of Population Genetic Diversity of Ranodon sibiricus in China Inferred from Mitochondrial DNA Control Region

以线粒体DNA(mitochondrial DNA,mtDNA)控制区为分子标记,对分布于新疆温泉县6处自然栖息地的新疆北鲵(Ranodon sibiricus)遗传多样性进行研究.共采集新疆北鲵尾端肌肉组织样本60份,通过PCR扩增获得853bp的mtDNA序列,含D-loop序列747bp、tRNA-Pro序列72bp及部分tRNA-Thr和tRNA-Pro之间基因间隔区(ISR)序列34bp,其中D-loop序列中A、T、G和C 4种核苷酸所占百分比分别为31.92%,35.04%,15.02%和18.02%,A+T所占百分比为66.96%.经MEGA软件比对发现,所得60个样品的扩增序列(853bp)完全一致,共享一个单倍型,所有扩增序列仅在控制区的第449位碱基(均为A)与GenBank(AJ419960)中新疆北鲵线粒体该位点碱基(为G)不一致.结果表明,国内现存6处自然栖息地内的新疆北鲵遗传多样性极低,在近缘同属种及脊椎动物中都极为罕见,显示该种近期经历过严重的瓶颈效应,可能由一个单倍型扩散至目前的分布格局.研究结果可为该物种保护提供分子遗传学依据.

The population genetic diversity of Siberian salamander（Ranodon sibiricus）in China was studied using mitochondrial DNA control region.A total of 60 samples were collected fromR.sibiricus tail of six habitats in Wenquan County,the only distribution area of R.sibiricusin China.For each sample,genomic DNA was extracted and the fragment of the mitochondrial DNA controling region（plus upstream proline tRNA,part of intergenic spacer region（ISR）between threonine and proline tRNAs）was amplified via PCR after sequencing,we obtained 853 bp sequences including 34 bp of partial ISR,72 bp tRNA-Pro,and 747 bp mtDNA control region.The average base compositions of the control region were 31.92%,35.04%,15.02%,18.02%for A,T,G,C,respectively.After aligning the 60 sequences in MEGA software,we found that they were all identical and shared one haplotype,differing from the one retrieved from the GenBank（accession number,AJ419960）at the 449 th site of control region,with A in our 60 sequences and G in the retrieved sequence.This result demonstrates that the Siberian salamanders have extremely low levels of genetic diversity.This phenomenon is rare among the closely related species and other vertebrates.It further suggests that R.sibiricus had experienced a serious bottleneck effect in the relatively recent past;and the current distribution pattern might result from the spread of one haplotype.Therefore,the existing R.sibiricus in Xinjiang province of China should be considered as one geographic group for management and protection.