Biology Department, Fordham University, 441 E. Fordham Road, Bronx, NY, 10458, USA.
Biology Department, Duke University, 130 Science Drive, Durham, NC, 27708, USA.
Am J Bot. 2021 May;108(5):857-868. doi: 10.1002/ajb2.1653. Epub 2021 May 3.
Invasive species are expected to undergo a reduction in genetic diversity due to founder effects, which should limit their ability to adapt to new habitats. Still, many invasive species achieve widespread distributions and dense populations. This paradox of invasions could potentially be overcome through multiple introductions or hybridization, both of which increase genetic diversity. We conducted a population genomics study of Japanese knotweed (Reynoutria japonica), which is a polyploid, clonally reproducing invasive species that has been notoriously successful worldwide despite supposedly low genetic diversity.
We used genotyping by sequencing to collect 12,912 SNP markers from 88 samples collected at 38 locations across North America for the species complex. We used alignment-free k-mer hashing analysis in addition to traditional population genetic analyses to account for the challenges of genotyping polyploids.
Genotypes conformed to three genetic clusters, likely representing Japanese knotweed, giant knotweed, and hybrid bohemian knotweed. We found that, contrary to previous findings, the Japanese knotweed cluster had substantial genetic diversity, though it had no apparent genetic structure across the landscape. In contrast, giant knotweed and hybrids showed distinct population groups. We did not find evidence of isolation by distance in the species complex, likely reflecting the stochastic introduction history of this species complex.
The results indicate that clonal invasive species can show substantial genetic diversity and can be successful at colonizing a variety of habitats without showing evidence of local adaptation or genetic structure.
由于奠基者效应，入侵物种的遗传多样性预计会减少，这应该限制它们适应新栖息地的能力。尽管遗传多样性较低，但许多入侵物种还是实现了广泛的分布和密集的种群。入侵的这种悖论可能会通过多次引入或杂交来克服，这两种方法都可以增加遗传多样性。我们对日本虎杖（Reynoutria japonica）进行了种群基因组学研究，它是一种多倍体、克隆繁殖的入侵物种，尽管据说遗传多样性较低，但在全球范围内却取得了巨大的成功。
我们使用测序基因型分析从北美 38 个地点的 88 个样本中收集了 12912 个 SNP 标记，这些样本来自该物种复合体。我们使用无比对 k-mer 哈希分析来解释多倍体基因分型的挑战，除此之外，还使用了传统的种群遗传分析。
基因型符合三个遗传聚类，可能代表日本虎杖、巨型虎杖和杂种波西米亚虎杖。我们发现，与之前的发现相反，日本虎杖聚类具有大量的遗传多样性，尽管它在整个景观中没有明显的遗传结构。相比之下，巨型虎杖和杂种显示出不同的群体。我们没有发现该物种复合体中存在隔离距离的证据，这可能反映了该物种复合体的随机引入历史。
结果表明，克隆入侵物种可以表现出大量的遗传多样性，并能够成功地在各种生境中定居，而没有表现出局部适应或遗传结构的证据。
