Cariou M, Duret L, Charlat S
Université de Lyon, Université Lyon 1, CNRS, UMR 5558, Laboratoire de Biométrie et Biologie Evolutive, Villeurbanne, France.
J Evol Biol. 2017 Dec;30(12):2204-2210. doi: 10.1111/jeb.13186. Epub 2017 Oct 23.
The spread of maternally inherited microorganisms, such as Wolbachia bacteria, can induce indirect selective sweeps on host mitochondria, to which they are linked within the cytoplasm. The resulting reduction in effective population size might lead to smaller mitochondrial diversity and reduced efficiency of natural selection. While documented in several host species, it is currently unclear if such a scenario is common enough to globally impact the diversity and evolution of mitochondria in Wolbachia-infected lineages. Here, we address this question using a mapping of Wolbachia acquisition/extinction events on a large mitochondrial DNA tree, including over 1000 species. Our analyses indicate that on a large phylogenetic scale, other sources of variation, such as mutation rates, tend to hide the effects of Wolbachia. However, paired comparisons between closely related infected and uninfected taxa reveal that Wolbachia is associated with a twofold reduction in silent mitochondrial polymorphism, and a 13% increase in nonsynonymous substitution rates. These findings validate the conjecture that the widespread distribution of Wolbachia infections throughout arthropods impacts the effective population size of mitochondria. These effects might in part explain the disconnection between genetic diversity and demographic population size in mitochondria, and also fuel red-queen-like cytonuclear co-evolution through the fixation of deleterious mitochondrial alleles.
母系遗传微生物（如沃尔巴克氏体细菌）的传播可诱导对宿主线粒体的间接选择性清除，它们在细胞质中与线粒体相连。有效种群大小的降低可能导致线粒体多样性减小以及自然选择效率降低。虽然在几种宿主物种中已有记载，但目前尚不清楚这种情况是否普遍到足以在全球范围内影响感染沃尔巴克氏体的谱系中线粒体的多样性和进化。在此，我们通过在一个包含1000多个物种的大型线粒体DNA树上绘制沃尔巴克氏体的获得/灭绝事件来解决这个问题。我们的分析表明，在大的系统发育尺度上，其他变异来源（如突变率）往往会掩盖沃尔巴克氏体的影响。然而，对密切相关的感染和未感染分类群进行配对比较发现，沃尔巴克氏体与线粒体沉默多态性降低两倍以及非同义替换率增加13%有关。这些发现证实了这样的推测，即沃尔巴克氏体感染在节肢动物中的广泛分布会影响线粒体的有效种群大小。这些影响可能部分解释了线粒体中遗传多样性与种群数量之间的脱节，并且还通过有害线粒体等位基因的固定推动类似红皇后效应的细胞核-细胞质共同进化。
