Wang Yi-Quan, Zhu Wei-Quan, Wang Chao-Lin
School of Life Science, Xiamen University, Xiamen 361005, China.
Yi Chuan Xue Bao. 2003 May;30(5):425-30.
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 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.
扬子鳄（Alligator sinensis）是中国一种极度濒危的特有物种，受到中国法律的保护。近期调查结果显示，在过去50年里，扬子鳄的数量持续下降，到2000年时，野外存活个体不足150只。为防止该物种灭绝，20世纪80年代初分别在安徽省宣州县和浙江省长兴县建立了两个养殖场。经过20年的繁育努力，圈养个体总数已增至9000多只，形成了两个独立的圈养亚种群，即宣州亚种群（XZSP）和长兴亚种群（CXSP）。由于缺乏圈养种群遗传多样性的相关信息，随机抽取了42只圈养个体进行研究，其中包括来自宣州亚种群的33只和长兴亚种群的9只，以调查其遗传状况，为下一步保护行动提供策略依据。本研究采用PCR方法，使用自行设计的引物扩增线粒体DNA控制区。PCR产物纯化后，所有扩增产物均使用ABI BigDye Terminator Cycle Sequencing Ready Reaction Kit和ABI 310基因分析仪直接测序。结果，从39个样本中获得了长度为462个碱基对的控制区5'端序列。序列比对显示，在所检测的个体中，该控制区此范围内没有任何变异位点，即这些扬子鳄仅共享该区域的一种单倍型。这一结果强烈表明，圈养扬子鳄种群的遗传多样性状况非常差。种群遗传多样性丧失的原因主要是种群衰退以及过去50年个体数量急剧减少。造成这种现象的另一个因素是圈养种群奠基者数量有限。最后，作者针对扬子鳄的遗传保护提出了三条建议。
