Pereira Ricardo J, Lima Thiago G, Pierce-Ward N Tessa, Chao Lin, Burton Ronald S
Division of Evolutionary Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, Munich, Germany.
Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA.
Mol Ecol. 2021 Dec;30(23):6403-6416. doi: 10.1111/mec.15985. Epub 2021 Jun 8.
Reproductive isolation is often achieved when genes that are neutral or beneficial in their genomic background become functionally incompatible in a foreign genomic background, causing inviability, sterility or other forms of low fitness in hybrids. Recent studies suggest that mitonuclear interactions are among the initial incompatibilities to evolve at early stages of population divergence across taxa. Yet, the genomic architecture of mitonuclear incompatibilities has rarely been elucidated. We employ an experimental evolution approach starting with low-fitness F interpopulation hybrids of the copepod Tigriopus californicus, in which frequencies of compatible and incompatible nuclear alleles change in response to an alternative mitochondrial background. After about nine generations, we observe a generalized increase in population size and in survivorship, suggesting efficiency of selection against maladaptive phenotypes. Whole genome sequencing of evolved populations showed some consistent allele frequency changes across three replicates of each reciprocal cross, but markedly different patterns between mitochondrial backgrounds. In only a few regions (~6.5% of the genome), the same parental allele was overrepresented irrespective of the mitochondrial background. About 33% of the genome showed allele frequency changes consistent with divergent selection, with the location of these genomic regions strongly differing between mitochondrial backgrounds. In 87% and 89% of these genomic regions, the dominant nuclear allele matched the associated mitochondrial background, consistent with mitonuclear co-adaptation. These results suggest that mitonuclear incompatibilities have a complex polygenic architecture that differs between populations, potentially generating genome-wide barriers to gene flow between closely related taxa.
当在其基因组背景中中性或有益的基因在异源基因组背景中功能不相容时，通常会实现生殖隔离，从而导致杂种出现 inviability、不育或其他形式的低适应性。最近的研究表明，线粒体-核相互作用是不同分类群种群分化早期阶段进化出的初始不相容性之一。然而，线粒体-核不相容性的基因组结构很少被阐明。我们采用实验进化方法，从桡足类加州虎斑猛水蚤的低适应性 F 种群间杂种开始，其中相容和不相容核等位基因的频率会因替代线粒体背景而发生变化。经过大约九代后，我们观察到种群规模和存活率普遍增加，这表明针对适应不良表型的选择是有效的。对进化种群的全基因组测序显示，每个正反交的三个重复样本中存在一些一致的等位基因频率变化，但线粒体背景之间的模式明显不同。在仅少数区域（约占基因组的 6.5%），无论线粒体背景如何，相同的亲本等位基因都过度富集。约 33%的基因组显示等位基因频率变化与分歧选择一致，这些基因组区域的位置在线粒体背景之间有很大差异。在这些基因组区域的 87%和 89%中，显性核等位基因与相关的线粒体背景相匹配，这与线粒体-核共同适应一致。这些结果表明，线粒体-核不相容性具有复杂的多基因结构，不同种群之间存在差异，可能会在密切相关的分类群之间产生全基因组范围的基因流动障碍。
