Flanagan Ben A, Krueger-Hadfield Stacy A, Murren Courtney J, Nice Chris C, Strand Allan E, Sotka Erik E
Department of Biology, College of Charleston, Charleston, SC, USA.
Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA.
Mol Ecol. 2021 May;30(9):1962-1978. doi: 10.1111/mec.15854. Epub 2021 Apr 9.
The genomic variation of an invasive species may be affected by complex demographic histories and evolutionary changes during the invasion. Here, we describe the relative influence of bottlenecks, clonality, and population expansion in determining genomic variability of the widespread red macroalga Agarophyton vermiculophyllum. Its introduction from mainland Japan to the estuaries of North America and Europe coincided with shifts from predominantly sexual to partially clonal reproduction and rapid adaptive evolution. A survey of 62,285 SNPs for 351 individuals from 35 populations, aligned to 24 chromosome-length scaffolds indicate that linkage disequilibrium (LD), observed heterozygosity (H ), Tajima's D, and nucleotide diversity (Pi) were greater among non-native than native populations. Evolutionary simulations indicate LD and Tajima's D were consistent with a severe population bottleneck. Also, the increased rate of clonal reproduction in the non-native range could not have produced the observed patterns by itself but may have magnified the bottleneck effect on LD. Elevated marker diversity in the genetic source populations could have contributed to the increased H and Pi observed in the non-native range. We refined the previous invasion source region to a ~50 km section of northeastern Honshu Island. Outlier detection methods failed to reveal any consistently differentiated loci shared among invaded regions, probably because of the complex A. vermiculophyllum demographic history. Our results reinforce the importance of demographic history, specifically founder effects, in driving genomic variation of invasive populations, even when localized adaptive evolution and reproductive system shifts are observed.
入侵物种的基因组变异可能受到入侵过程中复杂的种群统计学历史和进化变化的影响。在此，我们描述了瓶颈效应、克隆性和种群扩张在决定广泛分布的红色大型海藻——细基江蓠繁枝变种（Agarophyton vermiculophyllum）基因组变异性方面的相对影响。它从日本本土引入到北美和欧洲的河口，这一过程伴随着从主要有性繁殖向部分克隆繁殖的转变以及快速的适应性进化。对来自35个种群的351个个体的62285个单核苷酸多态性（SNP）进行的调查，这些SNP与24个染色体长度的支架比对后表明，非本地种群中的连锁不平衡（LD）、观察到的杂合度（H）、 Tajima's D和核苷酸多样性（Pi）均高于本地种群。进化模拟表明，LD和Tajima's D与严重的种群瓶颈效应一致。此外，非本地范围内克隆繁殖率的增加本身并不能产生观察到的模式，但可能放大了瓶颈效应在LD上的影响。遗传源种群中标记多样性的增加可能导致了在非本地范围内观察到的H和Pi的增加。我们将之前的入侵源区域细化到本州岛东北部约50公里的一段区域。异常值检测方法未能揭示入侵区域之间共享的任何一致分化的位点，这可能是由于细基江蓠繁枝变种复杂的种群统计学历史所致。我们的结果强化了种群统计学历史，特别是奠基者效应，在驱动入侵种群基因组变异中的重要性，即使观察到局部适应性进化和生殖系统转变时也是如此。
