Estimating the Frequencies of Genetically Distinct Classes of Individuals in Hybridized Populations
Estimating the Frequencies of Genetically Distinct Classes of Individuals in Hybridized Populations
复制标题
估计杂交群体中遗传上不同的个体类别的频率
DOI：
10.1093/oxfordjournals.jhered.a111268
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发表时间：
1993
影响因子：
3.1
通讯作者：
N. Ellstrand
中科院分区：
文献类型：
--
作者：
J. Nason;N. Ellstrand
杂交和种间重组导致分子标记的新形态和关联的形成。因此，在过去，通过鉴定表现出一些确定的杂交或回交表型或基因型的个体来推断杂交和基因渗入的存在。这种方法可能不可靠，因为它可能低估或高估杂交群体中不同类别个体的频率。此外，该方法没有提供正式的框架来测试特定类别的杂种或渐渗体的频率等于零的无效假设。提出了一种模型，该模型使用最大似然法和分离亲本物种特定等位基因的共显性分子标记来估计杂交群体中可能出现的六类个体的频率。如果满足模型假设，则对亲本物种、杂种和渗入个体的频率的估计是无偏的。如果违反模型假设，则渗入频率的估计是保守的。蒙特卡罗计算机模拟用于检查模型估计的偏差和方差，并评估不同采样策略的效果，因为具有独特等位基因的基因座数量、这些等位基因的频率以及采样的假定杂交个体的数量各不相同。还使用模拟来检查 delta 和 bootstrap 方法获得模型估计的真实方差的准确性。这种方法为进化遗传学家提供了一种简单的方法来量化自然群体中杂交和基因渗入的发生和程度。
Hybridization and interspecific recombination result in the formation of novel morphologies and associations of molecular markers. Thus, in the past, the existence of hybridization and introgression has been inferred by identifying individuals exhibiting some defined hybrid or backcross phenotypes or genotypes. This approach can be unreliable because it may under- or overestimate the frequency of different classes of individuals in a hybridized population. Also, this method provides no formal framework for testing a null hypothesis that the frequency of a particular class of hybrids or introgressants is equal to zero.A model is presented which uses the method of maximum likelihood and codominant molecular markers segregating for parental species specific alleles to estimate the frequencies of six classes of individuals that may occur in a hybridized population. Estimates of the frequency of parental species, hybrid, and introgressed individuals are unbiased if model assumptions are met. If model assumptions are violated, estimates of the frequency of introgression are conservative. Monte Carlo computer simulations are used to examine the bias and variance of the model estimates and to evaluate the effects of different sampling strategies as the number of loci with unique alleles, the frequencies of these alleles, and the number of putative hybrid individuals sampled are varied. Simulations were also used to examine the accuracy of delta and bootstrap methods of obtaining true variances of the model estimates. This approach provides evolutionary geneticists with a simple method to quantify the occurrence and extent of hybridization and introgression in natural populations.