Overath R D, Asmussen M A
Department of Genetics, University of Georgia, Athens 30602, USA.
Genetics. 1998 Apr;148(4):2029-39. doi: 10.1093/genetics/148.4.2029.
We extensively analyze the maintenance of genetic variation and deviations from Hardy-Weinberg frequencies at a diallelic locus under mixed mating with apomixis and constant viability selection. Analytical proofs show that: (1) at most one polymorphic equilibrium exists, (2) polymorphism requires overdominant or underdominant selection, and (3) a simple, modified overdominance condition is sufficient to maintain genetic variation. In numerical analyses, only overdominant polymorphic equilibria are stable, and these are stable whenever they exist, which happens for approximately 78% of random fitness and mating parameters. The potential for maintaining both alleles increases with increasing apomixis or outcrossing and decreasing selfing. Simulations also indicate that equilibrium levels of heterozygosity will often be statistically indistinguishable from Hardy-Weinberg frequencies and that adults, not seeds, should usually be censused to maximize detecting deviations. Furthermore, although both censuses more often have an excess rather than a deficit of heterozygotes, analytical sign analyses of the fixation indices prove that, overall, adults are more likely to have an excess and seeds a deficit at equilibrium.
我们广泛分析了在兼性无融合生殖和恒定生存力选择的混合交配情况下，双等位基因位点上遗传变异的维持以及与哈迪-温伯格频率的偏差。分析证明表明：（1）最多存在一个多态平衡；（2）多态性需要超显性或亚显性选择；（3）一个简单的、修正的超显性条件足以维持遗传变异。在数值分析中，只有超显性多态平衡是稳定的，并且只要它们存在就稳定，这种情况大约发生在78%的随机适合度和交配参数中。维持两个等位基因的潜力随着无融合生殖或异交的增加以及自交的减少而增加。模拟还表明，杂合子的平衡水平在统计学上通常与哈迪-温伯格频率没有区别，并且通常应该对成体而不是种子进行普查，以最大限度地检测偏差。此外，虽然两种普查中杂合子通常更多是过剩而不是不足，但固定指数的分析符号分析证明，总体而言，在平衡时成体更有可能出现过剩而种子更有可能出现不足。
