Multiple Introductions and Distinct Genetic Groups of Canada Goldenrod (Solidago canadensis) in China Revealed by Genomic Single-Nucleotide Polymorphisms

Despite numerous studies reported in the context of ecology, the introduction history of the infamous invasive plant Canada goldenrod (Solidago canadensis L.) remains elusive. In the present study, we explored the sources and the number of introduction events of this species from its native areas into China. Using the genotyping-by-sequencing approach, we identified 34,035 selectively neutral single-nucleotide polymorphism (SNP) markers to infer the evolutionary trajectories of 77 S. canadensis individuals. Both the principal component analysis and the ADMIXTURE analysis revealed two genetic groups that are sympatric to each other in China and suggested the absence of genetic admixtures. The phylogenetic analysis indicated three feasible introduction routes and multiple introduction events of Canada goldenrod into China. Specifically, the one from the USA directly into China, the other from the USA into China through Japan, and the third from the USA into China through Europe. Based on the site frequency spectrum of these identified SNPs, we inferred strong bottleneck events for both genetic groups, and that the multiple introductions did not rescue the decline of genetic diversity. To conclude, multiple introduction events, genetic bottlenecks, and potential human-mediated spread characterize the introduction history of Canada goldenrod in China. The present study harnesses the power of SNP data in deciphering the evolutionary trajectory of invasive plants and paves the way for future studies concerning the invasion mechanism of Canada goldenrod.