Nadachowska Krystyna, Babik Wieslaw
Jagiellonian University, Institute of Environmental Sciences, Kraków, Poland.
Mol Biol Evol. 2009 Apr;26(4):829-41. doi: 10.1093/molbev/msp004. Epub 2009 Jan 8.
Understanding the process of divergence requires the quantitative characterization of patterns of gene flow between diverging taxa. New and powerful coalescent-based methods give insight into these processes in unprecedented details by enabling the reconstruction of the temporal distribution of past gene flow. Here, we use sequence variation at eight nuclear markers and mitochondrial DNA (mtDNA) in multiple populations to study diversity, divergence, and gene flow between two subspecies of a salamander, the smooth newt (Lissotriton vulgaris kosswigi and Lissotriton vulgaris vulgaris) in Turkey. The ranges of both subspecies encompass mainly the areas of this important glacial refugial area. Populations in refugia where species have been present for a long time and differentiated in situ should better preserve the record of past gene flow than young populations in postglacial expansion areas. Sequence diversity in both subspecies was substantial (nuclear pi(sil) = 0.69% and 1.31%). We detected long-term demographic stability in these refugial populations with large effective population sizes (N(e)) of the order of 1.5-3 x 10(5) individuals. Gene trees and the isolation with migration (IM) analysis complemented by tests of nested IM models showed that despite deep, pre-Pleistocene divergence of the studied newts, asymmetric introgression from vulgaris to kosswigi has occurred, with signatures of recent gene flow in mtDNA and an anonymous nuclear marker, and evidence for more ancient introgression in nuclear introns. The distribution of migration times raises the intriguing possibility that even the initial divergence may have occurred in the face of gene flow.
了解分化过程需要对分化类群之间的基因流动模式进行定量表征。新的强大的基于溯祖理论的方法通过重建过去基因流动的时间分布，以前所未有的细节深入了解这些过程。在这里，我们利用多个种群中八个核标记和线粒体DNA（mtDNA）的序列变异，研究土耳其光滑蝾螈（Lissotriton vulgaris kosswigi和Lissotriton vulgaris vulgaris）两个亚种之间的多样性、分化和基因流动。两个亚种的分布范围主要涵盖这个重要的冰川避难区。长期存在并在原地分化的避难所种群应该比冰期后扩张地区的年轻种群更好地保存过去基因流动的记录。两个亚种的序列多样性都很高（核π(sil)=0.69%和1.31%）。我们在这些避难所种群中检测到长期的种群动态稳定性，有效种群大小（N(e)）约为1.5 - 3×10(5)个个体。基因树以及通过嵌套IM模型测试补充的隔离与迁移（IM）分析表明，尽管所研究的蝾螈在更新世前就已深度分化，但从普通蝾螈到科斯维吉蝾螈发生了不对称的基因渗入，线粒体DNA和一个匿名核标记中有近期基因流动的特征，并且核内含子中有更古老基因渗入的证据。迁移时间的分布引发了一个有趣的可能性，即甚至初始分化可能也是在基因流动的情况下发生的。
