Data from: Hybrid ‘superswarm’ leads to rapid divergence and establishment of populations during a biological invasion

Understanding the genetic background of invading species can be crucial information clarifying why they become invasive. Intraspecific genetic admixture among lineages separated in the native ranges may promote the rate and extent of an invasion by substantially increasing standing genetic variation. Here, we examined the genetic relationships among threespine stickleback that recently colonized Switzerland. This invasion results from several distinct genetic lineages that colonized multiple locations and have since undergone range expansions, where they coexist and admix in parts of their range. Using 17 microsatellites genotyped for 634 individuals collected from 17 Swiss and two non-Swiss European sites, we reconstruct the invasion of stickleback and investigate the potential and extent of admixture and hybridization among the colonizing lineages from a population genetic perspective. Specifically, we test for an increase in standing genetic variation in populations where multiple lineages coexist. We find strong evidence of massive hybridization early on, followed by what appears to be recent increased genetic isolation and the formation of several new genetically distinguishable populations, consistent with a hybrid ‘superswarm’. This massive hybridization and population formation event(s) occurred over approximately 140 years and likely fuelled the successful invasion of a diverse range of habitats. The implications are that multiple colonizations coupled with hybridization can lead to the formation of new stable genetic populations potentially kick-starting speciation and adaptive radiation over a very short timescale.

解析入侵物种的遗传背景，是阐明其成功入侵机制的核心依据。原生分布区内分化的谱系间发生的种内遗传混合，可通过显著提升种群现存遗传变异水平，加快入侵进程并扩大入侵范围。本研究针对近期定居瑞士的三棘刺鱼（threespine stickleback）的遗传亲缘关系展开分析。本次入侵由多个独立遗传谱系驱动：这些谱系先后定殖于多个区域并发生分布范围扩张，且在部分分布区内彼此共存并发生遗传混合。本研究对采自17个瑞士采样点与2个欧洲非瑞士采样点的634个个体，开展了17个微卫星标记（microsatellites）的基因分型，以此重建三棘刺鱼的入侵历史，并从群体遗传学视角探究定殖谱系间遗传混合与杂交发生的潜力及程度。具体而言，我们检验了多谱系共存种群的现存遗传变异水平是否出现提升。研究结果显示，入侵早期存在大规模杂交的显著证据，后续则出现了遗传隔离加剧的现象，并形成了多个可通过遗传特征区分的新种群，这与杂交‘超级类群’（hybrid superswarm）的特征相符。此次大规模杂交与种群形成过程历时约140年，极有可能助力三棘刺鱼成功入侵多样生境。本研究的启示在于：多次定殖事件与杂交作用相结合，可形成新的稳定遗传种群，甚至可能在极短时间内启动物种形成与适应性辐射过程。