Data from: The epigenetic footprint of poleward range-expanding plants in apomictic dandelions

Epigenetic modifications, such as DNA methylation variation, can generate heritable phenotypic variation independent of the underlying genetic code. However, epigenetic variation in natural plant populations is poorly documented and little understood. Here, we test if northward range expansion of obligate apomicts of the common dandelion (Taraxacum officinale) is associated with DNA methylation variation. We characterized and compared patterns of genetic and DNA-methylation variation in greenhouse-reared offspring of T. officinale that were collected along a latitudinal transect of northward range expansion in Europe. Genetic AFLP and epigenetic MS-AFLP markers revealed high levels of local diversity and modest but significant heritable differentiation between sampling locations and between the Southern, Central and Northern regions of the transect. Patterns of genetic and epigenetic variation were significantly correlated, reflecting the genetic control over epigenetic variation and/or the accumulation of lineage-specific spontaneous epimutations, which may be selectively neutral. In addition, we identified a small component of DNA methylation differentiation along the transect that is independent of genetic variation. This epigenetic differentiation might reflect environment-specific induction or, in case the DNA methylation variation affects relevant traits and fitness, selection of heritable DNA methylation variants. Such generated epigenetic variants might contribute to the adaptive capacity of individual asexual lineages under changing environments. Our results highlight the potential of heritable DNA methylation variation to contribute to population differentiation along ecological gradients. Further studies are needed using higher-resolution methods to understand the functional significance of such natural occurring epigenetic differentiation.表观遗传修饰（epigenetic modifications），例如DNA甲基化变异，能够在不依赖于基础遗传编码的前提下产生可遗传的表型变异。然而，当前学界对自然植物种群中的表观遗传变异的记载与认知均较为匮乏。本研究以普通蒲公英（Taraxacum officinale）的专性无融合生殖种群为对象，探究其向北分布范围扩张过程是否与DNA甲基化变异存在关联。我们对沿欧洲向北扩散的纬度样带采集的普通蒲公英温室繁育后代的遗传与DNA甲基化变异模式进行了表征与比较。通过遗传扩增片段长度多态性（AFLP）标记与表观遗传甲基化敏感扩增多态性（MS-AFLP）标记分析，结果显示采样点之间以及样带的南部、中部与北部区域之间存在高水平的局域多样性，同时存在程度适中但显著的可遗传分化。遗传变异与表观遗传变异的模式呈现显著相关性，这一方面反映了表观遗传变异受到遗传调控，另一方面也可能源于谱系特异性自发表观突变的积累——这类突变通常呈选择中性。此外，我们还在样带中发现了一小部分与遗传变异无关的DNA甲基化分化。这类表观遗传分化可能源自环境特异性诱导；若DNA甲基化变异影响相关性状与适合度，则也可能是对可遗传DNA甲基化变异的定向选择。此类产生的表观遗传变异，或可帮助无性繁殖谱系在环境变化中提升适应能力。本研究结果凸显了可遗传DNA甲基化变异在推动沿生态梯度的种群分化方面的潜力。未来需采用更高分辨率的研究方法，以阐明这类自然发生的表观遗传分化的功能意义。