PDF(Pubmed)
Abstract：
Human transport of species across oceans disrupts natural dispersal barriers and facilitates hybridization between previously allopatric species. The recent introduction of the North Pacific sea squirt, Ciona robusta, into the native range of the North Atlantic sea squirt, Ciona intestinalis, is a good example of this outcome. Recent studies have revealed an adaptive introgression in a single chromosomal region from the introduced into the native species. Here, we monitored this adaptive introgression over time, examining both the frequency of adaptive alleles at the core and the hitchhiking footprint in the shoulders of the introgression island by studying a thousand Ciona spp. individuals collected in 22 ports of the contact zone, 14 of which were sampled 20 generations apart. For that purpose, we developed a KASP multiplex genotyping approach, which proved effective in identifying native, nonindigenous and hybrid individuals and in detecting introgressed haplotypes. We found no early generation hybrids in the entire sample, and field observations suggest a decline in the introduced species. At the core region of the introgression sweep, where the frequency of C. robusta alleles is the highest and local adaptation genes must be, we observed stable frequencies of adaptive alien alleles in both space and time. In contrast, we observed erosion of C. robusta ancestry tracts in flanking chromosomal shoulders on the edges of the core, consistent with the second phase of a local sweep and a purge of hitchhiked incompatible mutations. We hypothesize that adaptive introgression may have modified the competition relationships between the native and invasive species in human-altered environments.
摘要：
人类跨海洋的物种运输破坏了自然的扩散障碍，并促进了以前的异域物种之间的杂交。最近推出的北太平洋海鞘，Cionarobusta,进入北大西洋海鞘的原生范围，小肠，是这个结果的一个很好的例子。最近的研究已经揭示了从引入到本地物种中的单个染色体区域中的适应性渗入。这里,随着时间的推移，我们监测了这种适应性渗入，通过研究一千个Cionaspp，检查核心适应性等位基因的频率和渗入岛肩膀上的搭便车足迹。在接触区的22个端口收集的个人，其中14个样本相隔20代。为此,我们开发了KASP多重基因分型方法，这证明在识别本地人方面是有效的，非土著和杂种个体，以及检测渗入的单倍型。我们在整个样本中没有发现早期杂种，野外观察表明引进物种的减少。在渗入扫描的核心区域，罗布斯塔等位基因的频率最高，局部适应基因必须是，我们观察到适应性外来等位基因在空间和时间上的稳定频率。相比之下,我们观察到C.robusta祖先在核心边缘的侧翼染色体肩部的侵蚀，与局部扫描的第二阶段和搭便车的不相容突变的清除一致。我们假设适应性渗入可能已经改变了人类改变环境中本地物种和入侵物种之间的竞争关系。
