Schierup M H
Department of Ecology and Genetics, Institute of Biology, University of Aarhus, DK-8000 Aarhus C, Denmark.
Genetics. 1998 Jun;149(2):1153-62. doi: 10.1093/genetics/149.2.1153.
The actual and effective number of gametophytic self-incompatibility alleles maintained at mutation-drift-selection equilibrium in a finite population subdivided as in the island model is investigated by stochastic simulations. The existing theory founded by Wright predicts that for a given population size the number of alleles maintained increases monotonically with decreasing migration as is the case for neutral alleles. The simulation results here show that this is not true. At migration rates above Nm = 0.01-0.1, the actual and effective number of alleles is lower than for an undivided population with the same number of individuals, and, contrary to Wright's theoretical expectation, the number of alleles is not much higher than for an undivided population unless Nm < 0.001. The same pattern is observed in a model where the alleles display symmetrical overdominant selection. This broadens the applicability of the results to include proposed models for the major histocompatibility (MHC) loci. For a subdivided population over a large range of migration rates, it appears that the number of self-incompatibility alleles (or MHC-alleles) observed can provide a rough estimate of the total number of individuals in the population but it underestimates the neutral effective size of the subdivided population.
通过随机模拟研究了在岛屿模型中有限群体中，处于突变-漂移-选择平衡状态下维持的配子体自交不亲和等位基因的实际数量和有效数量。赖特创立的现有理论预测，对于给定的种群大小，维持的等位基因数量会随着迁移率的降低而单调增加，就像中性等位基因的情况一样。这里的模拟结果表明并非如此。在迁移率高于Nm = 0.01 - 0.1时，等位基因的实际数量和有效数量低于个体数量相同的未分化群体，并且与赖特的理论预期相反，除非Nm < 0.001，等位基因数量不会比未分化群体高很多。在等位基因表现出对称超显性选择的模型中也观察到了相同的模式。这拓宽了结果的适用性，使其包括了主要组织相容性复合体（MHC）位点的提议模型。对于在大范围迁移率下的细分群体，似乎观察到的自交不亲和等位基因（或MHC等位基因）数量可以提供该群体中个体总数的粗略估计，但它低估了细分群体的中性有效大小。
