Data from: The Carpathians hosted extra-Mediterranean refugia-within-refugia during the Pleistocene Ice Age: genomic evidence from two newt genera

Part of Europe’s temperate species survived the Pleistocene glacial cycles in refugia north of the Mediterranean peninsulas. For one such extra-Mediterranean refugia, the Carpathians, an intricate ‘refugia-within-refugia’ scenario has been suggested, involving species surviving in multiple discrete glacial refugia. We test the Carpathian refugia-within-refugia hypothesis, employing genome-wide multilocus data sets for two newt species (Triturus cristatus and Lissotriton montandoni). We first use Bayesian clustering to delineate intraspecific evolutionary lineages. The number of intraspecific lineages identified, and the allocation of localities to these lineages, were used to construct testable hypotheses on the spatial arrangement of glacial refugia in both newt species. Next we employ approximate Bayesian computation to date whether these lineages are of Holocene (< 12 Ka) or Pleistocene (> 12 Ka) origin. We identify three intraspecific evolutionary lineages for T. cristatus and two for L. montandoni. For both newt species, intraspecific divergence is rooted in the Pleistocene, in line with species survival in distinct range fragments during the last glacial period. Hence, our findings firmly support the Carpathian refugia-within-refugia hypothesis. Furthermore, we show that mitochondrial DNA overestimates the age of intraspecific evolutionary lineages and we urge caution in basing refugia-within-refugia scenarios on mitochondrial DNA alone.

欧洲温带物种中有一部分在更新世冰期循环中，于地中海半岛以北的冰期避难所（refugia）中得以存续。针对超地中海冰期避难所之一的喀尔巴阡山脉（Carpathians），此前已有研究提出复杂的“避难所内嵌避难所”（refugia-within-refugia）情景，即物种可在多个离散的冰期避难所中存活。本研究针对喀尔巴阡山脉“避难所内嵌避难所”假说展开验证，采用冠北螈（*Triturus cristatus*）与蒙氏滑螈（*Lissotriton montandoni*）两种蝾螈的全基因组多位点数据集。我们首先通过贝叶斯聚类（Bayesian clustering）方法界定种内进化支系（intraspecific evolutionary lineages），基于鉴定得到的种内进化支系数量，以及各采样点在这些支系中的归属情况，构建可检验的假说以阐释两种蝾螈的冰期避难所空间分布格局。随后采用近似贝叶斯计算（approximate Bayesian computation）方法，估算这些支系的起源时间，判断其属于全新世（Holocene，<12 Ka）还是更新世（Pleistocene，>12 Ka）。本研究在冠北螈中鉴定出3个种内进化支系，在蒙氏滑螈中鉴定出2个种内进化支系。两种蝾螈的种内分化均起源于更新世，与物种在末次冰期于不同分布片段中存续的模式相符。因此，本研究结果为喀尔巴阡山脉“避难所内嵌避难所”假说提供了强有力的支持。此外，我们发现线粒体DNA（mitochondrial DNA, mtDNA）会高估种内进化支系的起源时间，特此呼吁学界在构建“避难所内嵌避难所”情景时，不应仅以线粒体DNA作为唯一依据。