日本鳗鲡(Anguilla japonica)和欧洲鳗鲡(A. anguilla)的微卫星差异

MICROSATELLITE VARIATION OF JAPANESE EEL (ANGUILLA JAPONICA) AND EUROPEAN EEL (A. ANGUILLA)

采用PCR扩增单位点微卫星的方法研究了日本鳗鲡 (Anguillajaponica)和欧洲鳗鲡(A anguilla)的遗传差异。结果表明 ,微卫星等位基因数目分布范围为 8— 2 6,35组被试 ( 5个分类单元各 7个位点 )的显著性检验的结果表明其杂合性显著缺乏 (P <0 0 1 ) ,日本鳗鲡的 4个亚种群的所有微卫星位点均偏离哈 温平衡 ,对日本鳗鲡种群分化进行的正合检验结果也否定了种内个体随机分布的假设。FST值为 0 0 0 98(P =0 0 0 0 4 8)揭示了日本鳗鲡亚种群内存在较弱但显著的遗传分化。各分类单元间的FST及RST逐一对应矩阵显示了日本鳗鲡与欧洲鳗鲡两个远缘种之间存在显著差异。计算Goldstein的遗传距离并由此推算出两个种的分化时间约为 2 0 0多万年。

The migratory behavior in life cycles of eel is still a mystery. In this article we applied microsatellite markers to investigate the genetic structure of Anguilla japonica and verify the panmixia hypothesis of eel in western Pacific Ocean. Furthermore we also tried to explore the evolutionary history of freshwater eels (A. japonica and A. anguilla). Allelic variation at a total of 7 microsatellites was examined among elvers of freshwater eels. The number of alleles at these loci ranged from 8 to 26. Thirty-five performed tests revealed significant deficits of heterozygotes (P<0.01). Significant departure from expectations of Hardy-Weinberg equilibrium (HWE) was found for all loci within four subpopulations of A. japonica,which rejected the panmixia hypothesis (Schmidt,1925). Also exact tests of population differentiation based on allelic frequency distribution refuted the hypothesis of random distribution of individuals among populations. Population structure in four subpopulations of A. japonica was recognized by a weak but significant global genetic differentiation (F ST) value of 0.0098 (P=0.00048;10000 iteration). Pairwise matrixes of F STand R STshowed the significant difference between two distant related species——A. japonica and A. anguilla. Results from Mantel test show that Pearson's correlation (r) of two matrices (genetic distance matrix of 4 A. japonica subpopulations to geographic distance matrix) is 0.2498 (1000 permutations). Obviously the geographic isolation of habitat may play an important role in shaping the genetic structure but the intrinsic reason may due to the hatchery variations. The divergent time of these two species calculated by Goldstein distance method is over 2 million years. The results may challenge the former theory about the distribution of freshwater eels. We can infer that eel may involve in the trans-Arctic exchange in its evolutionary history. Actually further evidences are required to prove our assumption about the distribution of freshwater eels.