Zhou Shu-Rong, Pannell John R
Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX13RB, UK.
Genet Res (Camb). 2010 Apr;92(2):127-40. doi: 10.1017/S0016672310000133.
Inbreeding depression has important implications for a wide range of biological phenomena, such as inbreeding avoidance, the evolution and maintenance of sexual systems and extinction rates of small populations. Previous investigations have asked how inbreeding depression evolves in single and subdivided populations through the fixation of deleterious mutations as a result of drift, as well as through the expression of deleterious mutations segregating in a population. These studies have focused on the effects of mutation and selection at single loci, or at unlinked loci. Here, we used simulations to investigate the evolution of genetic load and inbreeding depression due to multiple partially linked loci in metapopulations. Our results indicate that the effect of linkage depends largely on the kinds of deleterious alleles involved. For weakly deleterious and partially recessive mutations, the speed of mutation accumulation at segregating loci in a random-mating subdivided population of a given structure tends to be retarded by increased recombination between adjacent loci - although the highest numbers of fixation of slightly recessive mutant alleles were for low but finite recombination rates. Although linkage had a relatively minor effect on the evolution of metapopulations unless very low values of recombination were assumed, close linkage between adjacent loci tended to enhance population structure and population turnover. Finally, within-deme inbreeding depression, between-deme inbreeding depression and heterosis generally increased with decreased recombination rates. Moreover, increased selfing reduced the effective amount of recombination, and hence the effects of tight linkage on metapopulation genetic structure were decreased with increasing selfing. In contrast, linkage had little effect on the fate of lethal and highly recessive alleles. We compare our simulation results with predictions made by models that ignore the complexities of recombination.
近亲繁殖衰退对广泛的生物学现象具有重要影响，例如近亲繁殖回避、性系统的进化与维持以及小种群的灭绝率。先前的研究探讨了近亲繁殖衰退如何在单一和细分种群中通过漂变导致有害突变的固定，以及通过种群中分离的有害突变的表达而进化。这些研究聚焦于单个位点或不连锁位点的突变和选择效应。在此，我们使用模拟来研究集合种群中多个部分连锁位点导致的遗传负荷和近亲繁殖衰退的进化。我们的结果表明，连锁效应在很大程度上取决于所涉及的有害等位基因的种类。对于弱有害和部分隐性突变，在给定结构的随机交配细分种群中，分离位点处突变积累的速度往往会因相邻位点间重组增加而减缓——尽管轻微隐性突变等位基因固定数量最多的情况出现在低但有限的重组率下。尽管除非假设重组值非常低，连锁对集合种群的进化影响相对较小，但相邻位点间的紧密连锁往往会增强种群结构和种群更替。最后，种群内近亲繁殖衰退、种群间近亲繁殖衰退和杂种优势通常会随着重组率降低而增加。此外，自交增加会降低重组的有效量，因此随着自交增加，紧密连锁对集合种群遗传结构的影响会减小。相比之下，连锁对致死和高度隐性等位基因的命运影响较小。我们将模拟结果与忽略重组复杂性的模型所做的预测进行了比较。
