D-loop Sequence Variation of Mitochondrial DNA in Captive Chinese Alligator

扬子鳄 (Alligatorsinensis)是中国特有的珍稀爬行动物 ,至 2 0 0 0年 ,野生扬子鳄的个体数已不足 15 0条 ,作为保护这一物种的措施之一 ,先后于 80年代初建起了 2个养殖场 ,现人工繁殖的扬子鳄总数已达 90 0 0余条。为揭示扬子鳄种群遗传多样性 ,从两个饲养种群中采集了 42个个体的样品 ,其中宣州样品 33个 (XZSP) ,长兴样品 9个(CXSP) ,用PCR方法扩增mtDNA控制区 ,扩增产物纯化后直接用ABI 310全自动遗传分析仪荧光标记测序 ,得到其中 39个个体的mtDNA控制区 5′端 46 2bp的序列。经比对发现 ,39个个体间的 5′端mtDNA控制区没有任何变异位点 ,共享一种单元型 ,提示扬子鳄饲养种群的遗传多样性非常贫乏 ,造成这一结果的主要原因是近 5 0年来 ,扬子鳄种群衰退和数量迅速减少导致的遗传多样性丢失 ,其次是人工繁殖的群体同时受到始创者数量较少产生的瓶颈效应影响。针对扬子鳄遗传多样性的现状 ,作者最后就这一濒危动物遗传多样性的保护对策提出 3点建议。Chinese alligator,Alligator sinensis,is a critically endangered endemic species under legislative protection in China.Result of recent investigations revealed that number of the alligators was continuously declining in the past 50 years and less than 150 individuals were surviving in the wild until 2000 years.In order to prevent the extinguishing of this species,two breeding farms were set up in early 1980s at Xuanzhou county,Anhui Province and Changxing County, Zhejiang Province respectively.After twenty years of breeding efforts,the number of captive individuals has been brought up to more than 9 000 in total, forming two separate captive subpopulations,Xuanzhou subpopulation (XZSP) and Changxing subpopulation (CXSP).Because of lack of the information regarding genetic diversity of the captive populations, 42 captive individuals including 33 individuals from XZSP and 9 from CXSP were sampled randomly to investigate their genetic status for the strategy in the next protection action.PCR method was adopted for amplification of mitochodrial DNA control region using primers designed in this research.After purification of PCR products,all of amplicons were sequenced directly with ABI BigDye TM Terminator Cycle Sequencing Ready Reaction Kit and ABI 310 genetic analyzer.Consequently, 5′end of control region with length of 462 base pair was obtained from 39 samples.Sequence alignment shows there is no any variation site in this range of control region among the individuals assayed here, namely only one haplotype of the region shared by these alligators.This result strongly indicates that the population of captive Chinese alligator is in very poor genetic diversity status.Reasons for the losing of genetic diversity in the population are mainly attributed to population depression and number of individual decreasing sharply in the past 50 years.Another factor accounting for the phenomena is the limit of founder number of captive population.Finally,authors proposed three pieces of advice for the genetic conservation of Chinese alligator.教育部骨干教师资助计划项目 (GG -180 - 2 10 0 2 40 3 -1740 );; 江苏省“333工程”人才培养基金资助~