Chromosomal evolution is widely considered to be an important driver of speciation, as karyotypic reorganization can bring about the establishment of reproductive barriers between incipient species. One textbook example for genetic mechanisms of speciation are large-scale chromosomal rearrangements such as Robertsonian (Rb) fusions, a common class of structural variants that can drastically change the recombination landscape by suppressing crossing-over and influence gene expression by altering regulatory networks. Here, we explore the population structure and demographic patterns of a well-known house mouse Rb system in the Aeolian archipelago in Southern Italy using genome-wide data. By analyzing chromosomal regions characterized by different levels of recombination, we trace the evolutionary history of a set of Rb chromosomes occurring in different geographical locations and test whether chromosomal fusions have a single shared origin or occurred multiple times. Using a combination of phylogenetic and population genetic approaches, we find support for multiple, independent origins of three focal Rb chromosomes. The elucidation of the demographic patterns of the mouse populations within the Aeolian archipelago shows that an interplay between fixation of newly formed Rb chromosomes and hybridization events has contributed to shaping their current karyotypic distribution. Overall, our results illustrate that chromosome structure is much more dynamic than anticipated and emphasize the importance of large-scale chromosomal translocations in speciation.

中文翻译：

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重建岛屿上染色体小种的进化历史：天然家鼠种群的全基因组分析。

染色体进化被广泛认为是物种形成的重要驱动力，因为核型重组可以在初期物种之间建立生殖屏障。关于物种形成的遗传机制的一个教科书示例是大规模染色体重排，例如罗伯逊（Rb）融合，这是一类常见的结构变异，可以通过抑制交叉并通过改变调控网络来影响基因表达，从而极大地改变重组格局。在这里，我们使用全基因组数据，研究了意大利南部风沙群岛中一个著名的家鼠Rb系统的种群结构和人口统计学模式。通过分析以不同重组水平为特征的染色体区域，我们追踪出现在不同地理位置的一组Rb染色体的进化历史，并测试染色体融合是否具有单一的共同起源或发生多次。使用系统发育和种群遗传学方法的组合，我们发现支持三个焦点Rb染色体的多个独立来源。对风沙群岛内的小鼠种群的人口统计模式的阐明表明，新形成的Rb染色体的固定与杂交事件之间的相互作用有助于塑造其当前的核型分布。总的来说，我们的结果表明，染色体结构比预期的要动态得多，并强调了大规模染色体易位在物种形成中的重要性。