Division of Biological Sciences, University of Montana, Missoula, Montana 59812.
Department of Biological Sciences, University of Denver, Denver, CO 80210.
Genetics. 2018 Jul;209(3):845-859. doi: 10.1534/genetics.118.300840. Epub 2018 Apr 24.
Resolving the mechanistic and genetic bases of reproductive barriers between species is essential to understanding the evolutionary forces that shape speciation. Intrinsic hybrid incompatibilities are often treated as fixed between species, yet there can be considerable variation in the strength of reproductive isolation between populations. The extent and causes of this variation remain poorly understood in most systems. We investigated the genetic basis of variable hybrid male sterility (HMS) between two recently diverged subspecies of house mice, and We found that polymorphic HMS has a surprisingly complex genetic basis, with contributions from at least five autosomal loci segregating between two closely related wild-derived strains of One of the HMS-linked regions on chromosome 4 also showed extensive introgression among inbred laboratory strains and transmission ratio distortion (TRD) in hybrid crosses. Using additional crosses and whole genome sequencing of sperm pools, we showed that TRD was limited to hybrid crosses and was not due to differences in sperm motility between strains. Based on these results, we argue that TRD likely reflects additional incompatibilities that reduce hybrid embryonic viability. In some common inbred strains of mice, selection against deleterious interactions appears to have unexpectedly driven introgression at loci involved in epistatic hybrid incompatibilities. The highly variable genetic basis to F1 hybrid incompatibilities between closely related mouse lineages argues that a thorough dissection of reproductive isolation will require much more extensive sampling of natural variation than has been commonly utilized in mice and other model systems.
解决物种间生殖障碍的机制和遗传基础对于理解塑造物种形成的进化力量至关重要。内在的杂种不亲和性通常被认为在物种之间是固定的，但在种群之间的生殖隔离强度上可能存在相当大的差异。在大多数系统中，这种变异的程度和原因仍知之甚少。我们研究了两个最近分化的家鼠亚种之间可变杂种雄性不育（HMS）的遗传基础， 和 我们发现，多态性 HMS 具有惊人复杂的遗传基础，至少有五个常染色体基因座在两个密切相关的野生衍生品系之间分离。染色体 4 上的一个 HMS 连锁区域也在近交实验室品系中表现出广泛的基因渗入和杂种杂交中的传递比偏差（TRD）。通过额外的杂交和精子池的全基因组测序，我们表明 TRD 仅限于杂种杂交，而不是由于 品系之间的精子活力差异。基于这些结果，我们认为 TRD 可能反映了降低杂种胚胎活力的额外不兼容性。在一些常见的近交系小鼠中，对有害相互作用的选择似乎出人意料地导致了与上位杂种不兼容性相关的基因座的基因渗入。密切相关的鼠系之间 F1 杂种不兼容性的高度可变遗传基础表明，对生殖隔离的彻底剖析将需要比在小鼠和其他模型系统中通常使用的更广泛的自然变异抽样。
