Asmussen M A, Arnold J
Department of Genetics, University of Georgia, Athens 30602.
Theor Popul Biol. 1991 Jun;39(3):273-300. doi: 10.1016/0040-5809(91)90024-a.
We examine the generation of cytonuclear disequilibria by admixture and continued gene flow. General formulas analogous to the nuclear case are first derived showing that the allelic and genotypic disequilibria from admixture or population subdivision equal their expected value across the contributing (sub) populations plus the covariance across these sources between the cytoplasmic gene frequency and the relevant nuclear frequency. A detailed study is then presented of the cytonuclear dynamics, in a random-mating population under two different migration scenarios. In both cases closed-form solutions are given for all variables as a function of the initial conditions and relevant migration parameters. The dynamics of the gene frequencies and allelic disequilibria, which dominate each system, are the same as those involving two unlinked nuclear loci, while the dynamics of the genotypic disequilibria and cytonuclear frequencies have no nuclear counterpart. The continent-island formulation focuses on a population receiving continued immigration from a large source of constant composition. A major discovery is that cytonuclear disequilibria can transiently build up on the "island" to levels far exceeding those found at equilibrium. In contrast, the admixture formulation focuses on the dynamics within two populations undergoing continued intermigration. Although in this case all cytonuclear associations must ultimately decay to zero, long-term transient disequilibria can develop which are many times their initial admixture values. For both migration scenarios it is shown that the time of population censusing relative to migration and reproduction dramatically affects both the amount and pattern of the nonrandom associations produced. The empirical relevance of these models is discussed in light of nuclear-mitochondrial data from a hybrid zone between European and North American eels and from a zone of racial admixture in humans.
我们研究了混合和持续基因流导致的细胞核质不平衡的产生。首先推导了与核情况类似的通用公式，表明混合或种群细分产生的等位基因和基因型不平衡等于其在各贡献（亚）种群中的期望值加上细胞质基因频率与相关核频率在这些来源之间的协方差。然后详细研究了在两种不同迁移情景下随机交配种群中的细胞核质动态。在这两种情况下，都给出了所有变量作为初始条件和相关迁移参数函数的闭式解。主导每个系统的基因频率和等位基因不平衡的动态与涉及两个不连锁核基因座的动态相同，而基因型不平衡和细胞核质频率的动态则没有核对应物。大陆 - 岛屿模型关注的是一个持续接收来自组成恒定的大来源移民的种群。一个主要发现是，细胞核质不平衡可以在“岛屿”上短暂积累到远远超过平衡时发现的水平。相比之下，混合模型关注的是两个持续进行相互迁移的种群内部的动态。虽然在这种情况下所有细胞核质关联最终都必须衰减到零，但可以发展出长期的短暂不平衡，其值是初始混合值的许多倍。对于这两种迁移情景，都表明相对于迁移和繁殖的种群普查时间会显著影响所产生的非随机关联的数量和模式。根据欧洲和北美鳗鱼杂交区以及人类种族混合区的核 - 线粒体数据讨论了这些模型的实证相关性。
