Data from: Understanding the basis of diminished gene flow between hybridizing chromosome races of the house mouse

Speciation may be promoted in hybrid zones if there is an interruption to gene flow between the hybridizing forms. For hybridizing chromosome races of the house mouse in Valtellina (Italy) distinguished by whole-arm chromosomal rearrangements, previous studies have shown that there is greater interruption to gene flow at the centromeres of chromosomes that differ between the races than at distal regions of the same chromosome or at the centromeres of other chromosomes. Here, by increasing the number of markers along race-specific chromosomes, we reveal a decay in between-race genetic differentiation from the centromere to the distal telomere. For the first time, we use simulation models to investigate the possible role of recombination suppression and hybrid breakdown in generating this pattern. We also consider epistasis and selective sweeps as explanations for isolated chromosomal regions away from the centromere showing differentiation between the races. Hybrid breakdown alone is the simplest explanation for the decay in genetic differentiation with distance from the centromere. Robertsonian fusions/whole-arm reciprocal translocations are common chromosomal rearrangements characterizing both closely related species and races within species, and this fine-scale empirical analysis suggests that the unfitness associated with these rearrangements in the heterozygous state may contribute to the speciation process.若杂交类群间的基因流(gene flow)遭到阻断，杂交带(hybrid zones)中的物种形成(speciation)过程或可得到促进。针对意大利瓦尔泰利纳地区以全臂染色体重排(whole-arm chromosomal rearrangements)为特征的小家鼠杂交染色体宗(chromosome races)，既往研究显示，相较于同一染色体的远端区域或其他染色体的着丝粒(centromere)，类群间存在差异的染色体的着丝粒处的基因流受到的阻断更为显著。 本研究通过增加染色体宗特异性染色体上的遗传标记数量，揭示了类群间遗传分化从着丝粒向远端端粒(telomere)逐渐衰减的模式。本研究首次利用模拟模型(simulation models)探究重组抑制(recombination suppression)与杂交衰败(hybrid breakdown)在形成该格局中可能发挥的作用。此外，本研究还将上位性(epistasis)与选择性清除(selective sweeps)作为解释着丝粒以外孤立染色体区域存在类群间分化的潜在机制。仅靠杂交衰败即可最为简洁地解释遗传分化随距着丝粒距离增加而衰减的现象。 罗伯逊融合(Robertsonian fusions)/全臂相互易位(whole-arm reciprocal translocations)是近缘物种及物种类群内常见的染色体重排类型，此项精细尺度实证分析表明，杂合状态(heterozygous state)下与这类重排相关的适合度缺陷，或可推动物种形成过程。