Division of Biology, Kansas State University, Manhattan, KS 66506, USA.
Integr Comp Biol. 2019 Oct 1;59(4):900-911. doi: 10.1093/icb/icz025.
Mitochondria have been known to be involved in speciation through the generation of Dobzhansky-Muller incompatibilities, where functionally neutral co-evolution between mitochondrial and nuclear genomes can cause dysfunction when alleles are recombined in hybrids. We propose that adaptive mitochondrial divergence between populations can not only produce intrinsic (Dobzhansky-Muller) incompatibilities, but could also contribute to reproductive isolation through natural and sexual selection against migrants, post-mating prezygotic isolation, as well as by causing extrinsic reductions in hybrid fitness. We describe how these reproductive isolating barriers can potentially arise through adaptive divergence of mitochondrial function in the absence of mito-nuclear coevolution, a departure from more established views. While a role for mitochondria in the speciation process appears promising, we also highlight critical gaps of knowledge: (1) many systems with a potential for mitochondrially-mediated reproductive isolation lack crucial evidence directly linking reproductive isolation and mitochondrial function; (2) it often remains to be seen if mitochondrial barriers are a driver or a consequence of reproductive isolation; (3) the presence of substantial gene flow in the presence of mito-nuclear incompatibilities raises questions whether such incompatibilities are strong enough to drive speciation to completion; and (4) it remains to be tested how mitochondrial effects on reproductive isolation compare when multiple mechanisms of reproductive isolation coincide. We hope this perspective and the proposed research plans help to inform future studies of mitochondrial adaptation in a manner that links genotypic changes to phenotypic adaptations, fitness, and reproductive isolation in natural systems, helping to clarify the importance of mitochondria in the formation and maintenance of biological diversity.
线粒体一直被认为通过产生多布赞斯基-穆勒不相容性参与物种形成，其中线粒体和核基因组之间功能上的中性协同进化会导致等位基因在杂种中重组时出现功能障碍。我们提出，种群之间适应性的线粒体分歧不仅可以产生内在的（多布赞斯基-穆勒）不相容性，还可以通过自然选择和性选择对移民、合子前减数分裂隔离以及导致杂种适合度降低的外在因素来促进生殖隔离。我们描述了这些生殖隔离屏障如何通过线粒体功能的适应性分歧而潜在地产生，而这种分歧不需要线粒体-核协同进化，这与更确立的观点有所偏离。虽然线粒体在物种形成过程中的作用似乎很有前景，但我们也强调了知识的关键差距：（1）许多具有潜在线粒体介导生殖隔离的系统缺乏直接将生殖隔离与线粒体功能联系起来的关键证据；（2）线粒体屏障是否是生殖隔离的驱动因素或后果仍然有待观察；（3）在存在线粒体-核不相容性的情况下存在大量基因流，这引发了一个问题，即这种不相容性是否足够强大，足以驱动物种形成完成；（4）线粒体对生殖隔离的影响与多种生殖隔离机制同时存在时如何进行比较，这仍然需要进行测试。我们希望这种观点和提出的研究计划有助于以一种将基因型变化与自然系统中的表型适应性、适合度和生殖隔离联系起来的方式来告知未来对线粒体适应的研究，有助于澄清线粒体在生物多样性的形成和维持中的重要性。
