Einfeldt Anthony L, Jesson Linley K, Addison Jason A
Department of Biology University of New Brunswick Fredericton NB Canada.
Department of Biology Dalhousie University Halifax NS Canada.
Ecol Evol. 2020 May 24;10(13):6579-6592. doi: 10.1002/ece3.6391. eCollection 2020 Jul.
The same vectors that introduce species to new ranges could move them among native populations, but how human-mediated dispersal impacts native ranges has been difficult to address because human-mediated dispersal and natural dispersal can simultaneously shape patterns of gene flow. Here, we disentangle human-mediated dispersal from natural dispersal by exploiting a system where the primary vector was once extensive but has since ceased. From 10th to 19th Centuries, ships in the North Atlantic exchanged sediments dredged from the intertidal for ballast, which ended when seawater ballast tanks were adopted. We investigate genetic patterns from RADseq-derived SNPs in the amphipod ( = 121; 4,870 SNPs) and the annelid ( = 78; 3,820 SNPs), which were introduced from Europe to North America, have limited natural dispersal capabilities, are abundant in intertidal sediments, but not commonly found in modern water ballast tanks. We detect similar levels of genetic subdivision among introduced North American populations and among native European populations. Phylogenetic networks and clustering analyses reveal population structure between sites, a high degree of phylogenetic reticulation within ranges, and phylogenetic splits between European and North American populations. These patterns are inconsistent with phylogeographic structure expected to arise from natural dispersal alone, suggesting human activity eroded ancestral phylogeographic structure between native populations, but was insufficient to overcome divergent processes between naturalized populations and their sources. Our results suggest human activity may alter species' evolutionary trajectories on a broad geographic scale via regional homogenization and global diversification, in some cases precluding historical inference from genetic data.
将物种引入新分布范围的相同媒介也可能使它们在本地种群之间迁移，但是人类介导的扩散如何影响本地分布范围一直难以解决，因为人类介导的扩散和自然扩散会同时塑造基因流动模式。在这里，我们通过利用一个系统来区分人类介导的扩散和自然扩散，在这个系统中，主要媒介曾经广泛存在，但后来停止了。从10世纪到19世纪，北大西洋的船只用从潮间带挖出的沉积物作为压舱物进行交换，当采用海水压舱水舱时，这种情况就结束了。我们研究了来自欧洲引入到北美的两种生物的RADseq衍生SNP的遗传模式，一种是双足虾（样本量 = 121；4870个SNP），另一种是环节动物（样本量 = 78；3820个SNP），它们自然扩散能力有限，在潮间带沉积物中很丰富，但在现代压舱水舱中不常见。我们在引入的北美种群和欧洲本地种群中检测到了相似程度的遗传细分。系统发育网络和聚类分析揭示了不同地点之间的种群结构、分布范围内高度的系统发育网状结构以及欧洲和北美种群之间的系统发育分歧。这些模式与仅由自然扩散产生的系统地理结构不一致，这表明人类活动侵蚀了本地种群之间的祖先系统地理结构，但不足以克服归化种群与其来源之间的分化过程。我们的结果表明，人类活动可能通过区域同质化和全球多样化在广泛的地理尺度上改变物种的进化轨迹，在某些情况下排除了从遗传数据进行历史推断的可能性。
