Different waves of postglacial recolonisation and genomic structure of bank vole population in NE Poland

Previous studies indicated that in some species phylogeographic patterns
obtained in analyses of nuclear and mitochondrial DNA (mtDNA) markers can
be different. Such mitonuclear discordance can have important evolutionary
and ecological consequences. In the present study, we aimed to check if
there was any discordance between mitochondrial and nuclear DNA in the
bank vole population in the contact zone of its two mtDNA lineages. We
analysed the population genetic structure of bank voles using genome-wide
genetic data (SNPs) and diversity of sequenced heart transcriptomes
obtained from selected individuals from three populations inhabiting areas
outside the contact zone. The SNP genetic structure of the populations
confirmed the presence of at least two genetic clusters, and such division
was concordant with the patterns obtained in analyses of other genetic
markers and functional genes. However, genome-wide SNP analyses revealed a
more detailed structure of the studied population, consistent with more
than two bank vole recolonisation waves, as previously recognised in the
study area. We did not find any significant differences between
individuals representing two separate mtDNA lineages of the species in
functional genes coding for protein-forming complexes, which are involved
in the process of cell respiration in mitochondria. We concluded that the
contemporary genetic structure of the populations and the width of the
contact zone were shaped by climatic and environmental factors rather than
by genetic barriers. The studied populations were likely isolated in
separate Last Glacial Maximum refugia for an insufficient amount of time
to develop significant genetic differentiation.

既往研究表明，部分物种基于核DNA与线粒体DNA（mtDNA）标记分析得到的系统地理格局可能存在差异。这类线粒体-核基因组不谐和现象可产生重要的进化与生态后果。本研究旨在探究红背䶄（bank vole）在其两种线粒体DNA谱系接触带的种群中，线粒体与核DNA是否存在此类不谐和现象。我们利用全基因组遗传数据（单核苷酸多态性，SNPs）分析了红背䶄的种群遗传结构，并对栖息于接触带外区域的三个种群中的部分个体的心脏测序转录组多样性进行了分析。种群的单核苷酸多态性遗传结构证实至少存在两个遗传聚类，且该分化与其他遗传标记及功能基因分析得到的格局一致。然而，全基因组单核苷酸多态性分析揭示了研究种群更为精细的遗传结构，与该研究区域此前认定的不止两次红背䶄重新定殖浪潮相符。我们未发现该物种两个独立线粒体DNA谱系的个体在编码参与线粒体细胞呼吸过程的蛋白复合物的功能基因中存在显著差异。我们得出结论：种群当前的遗传结构及接触带的宽度主要由气候与环境因素塑造，而非遗传屏障。研究种群极有可能是在末次冰盛期的不同避难所中隔离，尚未经过足够时长以形成显著的遗传分化。