Data from: Massive invasion of exotic Barbus barbus and introgressive hybridisation with endemic B. plebejus in Northern Italy: where, how and why?

Biological invasions and introgressive hybridisation are major drivers for the decline of native freshwater fish. However, the magnitude of the problem across a native species range, the mechanisms shaping introgression as well as invader’s dispersal and the relative role of biological invasions in the light of multiple environmental stressors are rarely described. Here, we report extensive (N=665) mtDNA sequence and (N=692) microsatellite genotypic data of 32 Northern Adriatic sites aimed to unravel the invasion of the European Barbus barbus in Italy, and the hybridisation and decline of the endemic B. plebejus. We highlight an exceptionally fast breakthrough of B. barbus within the Po River Basin, leading to widespread introgressive hybridisation with the endemic B. plebejus within few generations. In contrast, adjacent drainage systems are still unaffected from B. barbus invasion. We show that barriers to migration are inefficient to halt the invasion process and that propagule pressure, and not environmental quality, is the major driver responsible for B. barbus success. Both introgressive hybridisation and invader’s dispersal are facilitated by ongoing fisheries management practices. Therefore, immediate changes in fisheries management (i.e. stocking and translocation measures) and a detailed conservation plan, focussed on remnant purebred B. plebejus populations, are urgently needed.

生物入侵与渐渗杂交是导致本土淡水鱼类种群衰退的关键驱动因素。然而，目前鲜有研究系统阐明该问题在本土物种分布范围内的危害程度、调控渐渗过程与入侵物种扩散的潜在机制，以及多重环境胁迫背景下生物入侵的相对作用。本研究报道了北亚得里亚海沿岸32个采样点的大规模分子数据：共获取665条线粒体DNA（mtDNA）序列，以及692份微卫星（microsatellite）基因型数据，旨在解析欧洲鲃（Barbus barbus）在意大利境内的入侵过程，以及地方性特有物种B. plebejus的杂交与种群衰退机制。研究结果显示，欧洲鲃在波河流域的入侵扩散速度极快，仅历经数代便与地方性特有物种B. plebejus发生了广泛的渐渗杂交。与之形成鲜明对比的是，邻近的水系尚未受到欧洲鲃入侵的波及。本研究证实，迁移障碍无法有效阻断欧洲鲃的入侵进程，而推动其入侵成功的核心因素为繁殖体压力（propagule pressure），而非环境质量。当前的渔业管理实践同时促进了渐渗杂交与入侵物种的扩散。因此，亟需立即调整渔业管理措施（即增殖放流与物种迁移方案），并针对残存的纯种B. plebejus种群制定详尽的保护计划。