样本容量对养殖群体内主要遗传结构分析参数的影响

Effects of sample size on various genetic structure parameter in cultured population genetic study

用微卫星标记评估养殖群体的遗传结构，设置8个取样量梯度，5个标记量梯度，统计分析了各遗传参数的变化。结果：群体等位基因数（A）随样本量的增加而呈现上升趋势，但上升幅度由0．6667-0．9615（10〈n〈30）下降到0．2308-0．3333（30〈n〈50）；46．15％的位点出现高频率等位基因即等位基因纯合化趋势，这可能与养殖群体长期受选择压力的影响有关。等位基因纯合化使多数位点的有效等位基因数（Ae）、期望杂合度（Ho）及多态信息含量（PIC）在样本量大于40时，在多个标记量梯度其变动范围均变小，并出现平台现象。样本量、微卫星标记的数量和多态性水平对群体遗传结构均有较大的影响，建议在用微卫星进行群体遗传评估时，标记的数量在20个以上，样本容量大小在40-50之间较为适合。

This study examines the effects of sample size on various genetic structure parameters. The population genetic structure of cultured mirror carp （Cyprinus carpio ） was estimated using mierosatellite markers. 8 different sample sizes and 5 marker numbers were set up to analyze most genetic parameters including population alleles distribution, allele numbers （A）, effect allele numbers （Ae）, observed heterozygosity （Ho）, expected heterozygosity （He） and polymorphism information content （PIC）. As a result, population allele numbers rise dramatically along with sample sizes from 10 to 40 and then held a steady increase trends. Meanwhile 46. 15% of loci showed high frequency allele. The results indicate that cultured population show predominant alleles in most loci because of selection pressure. Due to many homozygosity, the change of effect allele numbers, expected heterozygosity and polymorphism information content are little when the sample size is more than 40. In addition, the number of microsatellite markers and polymorphism level also have a little effect on the estimation of population genetic structure. So, we suggested that the numbers of markers is more than 20 and sample size is 40 to 50 when using microsatellite markers to estimate population genetic structure.