Data from: The role of chromosomal rearrangements and geographical barriers in the divergence of lineages in a South American subterranean rodent (Rodentia: Ctenomyidae: Ctenomys minutus)

Identifying factors and the extent of their roles in the differentiation of populations is of great importance for understanding the evolutionary process in which a species is involved. Ctenomys minutus is a highly karyotype- polymorphic subterranean rodent, with diploid numbers ranging from 42 to 50 and autosomal arm numbers ranging from 68 to 80, comprising a total of 45 karyotypes described so far. This species inhabits the southern Brazilian coastal plain, which has a complex geological history, with several potential geographical barriers acting on different time scales. We assessed the geographical genetic structure of C. minutus, examining 340 individuals over the entire distributional range and using information from chromosomal rearrangements, mitochondrial DNA (mtDNA) sequences, and 14 microsatellite loci. The mtDNA results revealed 7 main haplogroups, with the most recent common ancestors dating from the Pleistocene, whereas clustering methods defined 12 populations. Some boundaries of mtDNA haplogroups and population clusters can be associated with potential geographical barriers to gene flow. The isolation by distance pattern also plays an important role in fine-scale genetic differentiation, which is strengthened by the narrowness of the coastal plain and by common features of subterranean rodents (i.e., small fragmented populations and low dispersal rates), which limit gene flow among populations. A step-by-step mechanism of chromosomal evolution can be suggested for this species, mainly associated with the metapopulation structure, genetic drift, and the geographical features of the southern Brazilian coastal plain. However, chromosomal variation plays no or very little role in the diversification of C. minutus populations.

明确种群分化的影响因子及其作用程度，对于理解物种所处的演化进程具有重要意义。小栉鼠（Ctenomys minutus）是一类具有高度核型多态性的地下啮齿类，其二倍体染色体数范围为42至50，常染色体臂数范围为68至80，目前已报道的核型共计45种。该物种栖息于巴西南部沿海平原，该区域地质历史复杂，存在多个不同时间尺度上形成的潜在地理屏障。本研究针对C. minutus的地理遗传结构展开分析：在其完整分布范围内采集了340个个体，并结合染色体重排、线粒体DNA（mtDNA）序列以及14个微卫星位点的遗传信息进行研究。线粒体DNA分析结果显示存在7个主要单倍群，其最近共同祖先可追溯至更新世时期；而聚类分析方法则划分出12个种群。部分线粒体DNA单倍群与种群聚类的分界区域，可对应于阻碍基因交流的潜在地理屏障。距离隔离模式同样对精细尺度的遗传分化具有重要作用，巴西南部沿海平原的狭窄地理特征，以及地下啮齿类固有的种群特征（即种群小型化且呈片段化分布、扩散能力低下）进一步强化了这一效应，进而限制了种群间的基因交流。本研究推测C. minutus的染色体演化遵循逐步演化机制，该机制主要与集合种群结构、遗传漂变以及巴西南部沿海平原的地理特征相关。但染色体变异对C. minutus的种群分化并未起到显著作用，或仅起到极微弱的影响。