Isoëtes L. is a cosmopolitan genus comprising about 200 species, almost half of them being allo- or autopolyploids. We investigated the origin of decaploid I. lacustris using next generation sequencing (NGS). We sequenced the second intron of LEAFY (LFYint2) and analysed the morphology of seven samples of I. lacustris from five localities from East Europe and West Siberia. We have shown that I. lacustris is an allopolyploid having in its genome the subgenomes of the North American diploid I. prototypus, tetraploid I. tuckermanii (which contains subgenomes of diploid I. viridimontana and unknown species), and one more unknown diploid progenitor. NGS showed high reproducibility, demonstrating the same sets of LFYint2 copies in all the samples. The potential fifth subgenome has not been found, most likely due to a loss of the LEAFY gene as a result of subgenome reduction, as is characteristic of polyploids. These data imply that the ancestor of I. lacustris most likely originated in the north-east of North America (New England and Acadian region) where I. prototypus, I. tuckermanii and I. viridimontana co-occur, and that I. lacustris then spread to Eurasia via the North Atlantic Land Bridge. NGS-based amplicon sequencing has the potential to evaluate the ratio of frequency of different copies and to distinguish allopolyploidy and autopolyploidy (if the PCR efficiency of each of the copies is taken into account). This is especially useful, given that both play a prominent role in Isoëtes evolution. We also demonstrate that widely adopted cloning of LFYint2 in Isoëtes leads to biased results due to the amplification errors.

伊索埃特斯（IsoëtesL .）是世界性大类，约有200种，其中几乎一半是同种或同种多倍体。我们调查了十倍体I的起源。使用下一代测序（NGS）的湖相湖。我们对LEAFY的第二个内含子（LFYint2）进行了测序，并分析了7个I样品的形态。来自东欧和西西伯利亚五个地区的湖相湖。我们证明了我。lacustris是一种异源多倍体，在其基因组中具有北美二倍体I的亚基因组。prototypus四倍体我。tuckermanii（包含二倍体的亚基因组我。viridimontana和未知物种），以及另外一个未知的二倍体祖细胞。NGS显示出高重现性，在所有样品中均显示出相同的LFYint2拷贝。尚未发现潜在的第五个亚基因组，这很可能是由于亚基因组减少而导致的LEAFY基因缺失，这是多倍体的特征。这些数据暗示的祖先一湖生最有可能起源于东北北美（新英格兰和阿卡迪亚区），其中的我。prototypus，我。塔克曼尼和我。viridimontana并发，而我。湖泊然后通过北大西洋陆地桥梁传播到欧亚大陆。基于NGS的扩增子测序可以评估不同拷贝的频率比率，并区分同种多倍体和自体多倍体（如果考虑到每个拷贝的PCR效率）。鉴于两者在Isoëtes进化中都扮演着重要角色，因此这特别有用。我们还证明，由于扩增错误，在isotes中广泛采用的LFYint2克隆会导致结果有偏差。