No evidence for local adaptation and an epigenetic underpinning in native and non-native ruderal plant species in Germany

1. Many invasive species have rapidly adapted to different environments in their new ranges. This is surprising, as colonisation is usually associated with reduced genetic variation. Heritable phenotypic variation with an epigenetic basis may explain this paradox.
2. Here, we assessed the contribution of DNA methylation to local adaptation in native and naturalized non-native ruderal plant species in Germany. We reciprocally transplanted offspring from natural populations of seven native and five non-native plant species between the Konstanz region in the south and the Potsdam region in the north of Germany. Before the transplant, half of the seeds were treated with the demethylation agent zebularine. We recorded survival, flowering probability and biomass production as fitness estimates. 3. Contrary to our expectations, we found little evidence for local adaptation, both among the native and among the non-native plant species. Zebularine treatment had mostly negative effects on overall plant performance, regardless of whether plants were local or not, and regardless of whether they were native or non-native. 4. Synthesis. We conclude that local adaptation, at least at the scale of our study, plays no major role in the success of non-native and native ruderal plants. Consequently, we found no evidence yet for an epigenetic basis of local adaptation.

1. 诸多入侵物种已在其新生境中快速适应了多样的环境条件。这一现象颇为反常，因为物种定植通常伴随着遗传变异（genetic variation）水平的降低。而具备表观遗传（epigenetic）基础的可遗传表型变异，或可解释这一悖论。
2. 本研究以德国本土与归化外来杂草类植物为研究对象，评估了DNA甲基化（DNA methylation）在本地适应过程中的作用。我们将7个本土植物物种种群、5个非本土植物物种种群的子代，在德国南部康斯坦茨（Konstanz）地区与北部波茨坦（Potsdam）地区之间开展了交互移植实验。实验前，我们将半数种子用脱甲基试剂泽布拉林（zebularine）进行处理。我们记录了植株存活率、开花概率与生物量产出，以此作为适合度的评估指标。
3. 与我们的预期相悖的是，无论是本土植物还是非本土植物类群，我们均未发现本地适应的显著证据。无论植株是否为本地种群、无论其属于本土还是非本土物种，泽布拉林处理大多会对植株整体生长表现产生负面影响。
4. 综合结论：我们认为，至少在本研究的尺度范围内，本地适应并非本土与非本土杂草类植物成功定植的主要驱动因素。因此，目前我们尚未发现本地适应具备表观遗传基础的相关证据。