Data from: Genomic evidence of hybridization between two independent invasions of European green crab (Carcinus maenas) in the Northwest Atlantic

Invasive species have been associated with significant negative impacts in their introduced range often outcompeting native species, yet the long-term evolutionary dynamics of biological invasions are not well understood. Hybridization, either among waves of invasion or between native and introduced populations, could alter the ecological and evolutionary impacts of invasions yet has rarely been studied in marine invasive species. The European green crab (Carcinus maenas) invaded eastern North America twice from northern and southern locations in its native range. Here we examine the frequency of hybridization among these two distinct invasions at locations from New Jersey, USA to Newfoundland, Canada using restriction-site associated DNA sequencing (RAD-seq), microsatellite loci, and COI mtDNA sequences. We used Bayesian clustering and hybrid assignment analyses to investigate hybridization between the northern and southern populations. Of the samples analyzed, six locations contained at least one hybrid individual, while two locations were characterized by extensive hybridization, with 95% of individuals collected from Placentia Bay, Newfoundland being hybrids (mostly F2), and 90% of individuals from Kejimkujik, Nova Scotia being classified as hybrids, mostly backcrosses to the northern ecotype. The presence of both F2 hybrids and backcrossed individuals suggests that these hybrids are viable and introgression is occurring between invasions. Our results provide insight into the demographic and evolutionary consequences of hybridization between independent invasions, and will inform the management of green crabs in eastern North America.

外来入侵物种在其入侵区域内往往会对本地生态系统造成显著负面影响，且常通过竞争排挤本地物种，但目前学界对生物入侵的长期进化动态仍缺乏充分认知。杂交——无论是多波入侵事件间的杂交，还是本地种群与入侵种群间的杂交——可能会改变入侵事件的生态与进化影响，但目前针对海洋入侵物种的相关研究仍较为匮乏。欧洲绿蟹（Carcinus maenas）分别从其自然分布区的北部与南部两个区域，先后两次入侵北美东部海域。本研究以美国新泽西州至加拿大纽芬兰岛的多个采样点为研究区域，利用限制性酶切位点相关DNA测序（restriction-site associated DNA sequencing, RAD-seq）、微卫星位点以及COI线粒体DNA序列，分析这两次独立入侵种群间的杂交发生频率。研究采用贝叶斯聚类分析与杂交个体归属分析方法，探究北部与南部入侵种群间的杂交情况。在本次分析的所有样本中，共有6个采样点至少存在1个杂交个体；另有2个采样点表现出大范围的杂交现象：加拿大纽芬兰岛普拉森舍湾的采样个体中95%为杂交个体（以F2代为主），而新斯科舍省凯吉姆库吉克的采样个体中90%被归类为杂交个体，且多数为与北部生态型的回交个体。F2代杂交个体与回交个体的同时存在，表明这些杂交个体具有生存能力，且两次入侵种群间正在发生基因渐渗。本研究结果揭示了独立入侵种群间杂交的种群动态与进化后果，同时可为北美东部海域欧洲绿蟹的综合治理提供科学参考。