长江不同江段青虾的遗传多样性

Genetic diversity of Macrobrachium nipponense on a regional scale in the Yangtze River

利用20个微卫星分子标记对长江不同江段共6个青虾群体进行了遗传多样性分析,采样点包括重庆、万州、宜昌、武汉、九江和江阴。结果表明,6个青虾群体平均等位基因数(A)为5.25,平均有效等位基因数(Ne)为3.4622;20个位点平均多态信息含量(PIC)为0.5894;期望杂合度(He)由高到低依次为江阴群体(0.6308)、九江群体(0.6096)、宜昌群体(0.5945)、武汉群体(0.5934)、万州群体(0.5844)、重庆群体(0.5821),平均值为0.6296。分子方差分析(AMOVA)结果表明长江青虾6群体间遗传变异6.92%来自群体间,93.08%来自群体内部,两两群体间FST值在0.0253～0.0838(P<0.05)之间,表明群体间已明显出现分化,但分化程度中等,与湖泊青虾群体相比,长江各群体间遗传分化程度较弱,可能是由于流动的江水增加了群体间的交流。Hardy-Weinberg遗传平衡分析表明,6群体均出现杂合子缺失现象,可能是由于稀有等位基因缺失或无效等位基因造成;6群体间遗传距离为0.0620～0.1809,UPGMA聚类分析表明,江阴群体单独聚为一类,其余5个群体聚为另一类,其中九江和武汉群体最先聚到一起,其次万州、宜昌和重庆群体聚为一类。

Oriental river prawn （Macrobrachium nipponense） is one of the most important freshwater prawns for aquaculture in China. However, M. nipponense farming recently declined due to genetic retrogression. Its genetic diversity of different populations in the Yangtze River with microsatellite markers was investgated in order to give support to conservation and utilization of wild resources of M. nipponense. Twenty polymorphic microsatellite markers were applied to investigate the genetic diversity of 6 M. nipponense populations in the Yangtze River. The sampling sites included Chongqing, Wanzhou, Yichang, Wuhan, Jiujiang and Jiangyin. The average number of alleles （A） and effective numbers of alleles （Ne ） in 6 populations were 5.25 and 3. 462 2 respectively. The mean PIC value of 20 microsatellite loci was 0. 589 4. Expected heterozygosity （ Hc ） of 6 populations was as follows： Jiangyin （0. 630 8 ）, Jiujiang （0. 609 6 ）, Yichang （0.594 5）, Wuhan （0. 593 4）, Wanzhou （0.584 4） and Chongqing （0. 582 1 ）, and their mean value was 0. 629 6. The analysis of molecular variance （AMOVA） indicated that almost majority of the variance in the M. nipponense was within populations （93.08 % ） , and 6.92 % was among populations. The FST values between populations were 0. 025 3 - 0. 083 8 （ P 〈 0. 05 ）, which showed the genetic divergence between populations in the Yangtze River was intermediate but lower than that in the lakes. It was probably because running water promoted the exchanges between populations. Hardy-Weinberg equilibrium analysis indicated that deficiency of heterozygote existed in all of 6 populations, which was probably because of rare allele deficiency or null alleles. The genetic distances among populations ranged from 0. 062 0 to 0. 180 9. The UPGMA tree showed that Jiangyin stock formed an independent clade and resident 5 populations formed another one in which Jiujiang and Wuhan populations clustered at first.