长江口江豚的遗传多样性现状及种群动态

Analysis of genetic diversity and population dynamics of the narrow-ridged finless porpoise in the Yangtze River Estuary

长江口地处长江与东海、黄海的交汇处,是窄脊江豚东亚亚种和长江亚种的重叠分布区和死亡率高发区。筛选出16个多态性微卫星位点,对采自长江口的36头窄脊江豚东亚亚种样本作了遗传多样性和种群动态分析。结果显示,除了2个微卫星位点显著偏离了Hardy-Weinberg平衡外,其他14个位点均未偏离Hardy-Weinberg平衡。16个微卫星位点共获得了129个等位基因,平均等位基因数达8. 1个。计算获得的平均观察杂合度(Ho)为0. 733,平均期望杂合度(He)为0. 758,多态性信息含量(PIC)均在0. 5以上。其遗传多样性水平与印度洋江豚和海豹等海洋哺乳动物相近,但明显高于大熊猫、东北虎等陆生珍稀哺乳动物。杂合度检验和Mode-shift模型分析显示,该种群未经历过近期的遗传瓶颈效应。Msvar软件的4次模拟均未发现该种群在历史上发生过明显的有效数量波动,估算的当前有效种群大小约为5 623头。研究显示,在长江口发现的窄脊江豚东亚亚种个体,属于一个大而稳定的种群。

Located at the confluence of the East China Sea and the Yellow Sea,the Yangtze River Estuary is the area of overlapping distribution for two subspecies of the narrow-ridged finless porpoise（Neophocaena asiaeorientalis）.In recent years,finless porpoise deaths occur frequently in this area,which has aroused widespread concern of the public.In this study,the genetic diversity and population dynamics were investigated using 16 polymorphic microsatellite loci in 36 samples of the East Asian finless porpoise（N.asiaeorientalis sunameri）from the Yangtze River Estuary.The results showed that 14 microsatellite loci did not deviate from Hardy-Weinberg equilibrium except for 2 loci.A total of 129 alleles were obtained in all of16 loci with an average number 8.1.The average of observed heterozygosity（Ho）was 0.733;the average of expected heterozygosity（He）was 0.758,and the value of the polymorphism information content（PIC）was above 0.5.The level of genetic diversity is similar to marine mammals such as the Indian-Pacific finless porpoise（N.phocaenoides）and the seal（Phoca largha）,but significantly higher than valuable terrestrial mammals such as the giant panda（Ailuropoda melanoleuca）and the Amur tiger（Panthera tigris altaica）.In addition,the heterozygosity excess test and Mode-shift analysis showed that the population has not experienced genetic bottleneck effects during the recent historical period.Meanwhile,4 simulations on Msvar software exhibited virtually no detectable effective population size change in their recent past,and estimated the recent effective population size about 5 623 individuals,which revealed that the population of N.asiaeorientalis sunameri is large and stable in the Yangtze River Estuary.