提出问题：Relative contributions of pre-existing vs de novo genomic variation to adaptation are poorly understood, especially in polyploid organisms. 

主要研究：We assess this in high resolution using autotetraploid Arabidopsis arenosa, which repeatedly adapted to toxic serpentine soils that exhibit skewed elemental profiles. 

结果1-平行选择：Leveraging a fivefold replicated serpentine invasion, we assess selection on SNPs and structural variants (TEs) in 78 resequenced individuals and discover significant parallelism in candidate genes involved in ion homeostasis. 

结果2-建模：We further model parallel selection and infer repeated sweeps on a shared pool of variants in nearly all these loci, supporting theoretical expectations.

结果3-例外：A single striking exception is represented by TWO PORE CHANNEL 1, which exhibits convergent evolution from independent de novo mutations at an identical, otherwise conserved site at the calcium channel selectivity gate. 

结论：Taken together, this suggests that polyploid populations can rapidly adapt to environmental extremes, calling on both pre-existing variation and novel polymorphisms.

 摘 要 

先前已存在的或者从头新的基因组变异对于植物适应性的贡献大小并不清楚，尤其是在多倍体植物中。本文中，作者在同源四倍体植物Arabidopsis arenosa中评估了这两种基因组变异对于植物适应性的影响，该物种反复适应有毒的蛇纹岩土（元素不平衡，富含镁、镍、钴元素）。基于A. arenosa五个生存在蛇纹岩土的群体，作者评估了78个重测序个体中对于SNP和结构变体（TE）的选择，发现参与离子稳态的候选基因具有显著的平行选择。作者进一步对平行选择进行建模，推断几乎所有这些基因座发生了类似的选择清除，结果支持理论预期。其中，存在一个明显的例外，即TPC1基因在钙离子通道选择门的一个相同或保守的位点上，表现出独立从头突变的趋同演化。综上所述，本文的研究结果表明多倍体种群能够快速适应极端环境，既需要先前已存在的变异，也需要新的多态性。