Data from: Species introduction promotes hybridization and introgression in Coregonus: is there sign of selection against hybrids?

Species introductions are considered one of the major drivers of biodiversity loss via ecological interactions and genetic admixture with local fauna. We examined two well-recognized fish species, native whitefish (Coregonus lavaretus) and introduced vendace (C. albula), as well as their morphological hybrids in a single lake to test for selection against hybrids and backcrosses in the wild. A representative random subsample of 693 individuals (27.8%) was taken from the total catch of coregonids. This subsample was examined with the aim to select circa 50 individuals of pure whitefish (n=52), pure vendace (n=55) and putative hybrid (n=19) for genetic analyses. The subsequent microsatellites and mitochondrial (mt) DNA analyses provided compelling evidence of hybridization and introgression. Of the 126 fish examined, four were found to be F1, 14 backcrosses to whitefish, and seven backcrosses to vendace. The estimates of historical gene flow suggested higher rates from introduced vendace into native whitefish than vice versa, whereas estimates of contemporary gene flow were equal. Mitochondrial introgression was skewed, with 18 backcrosses having vendace mtDNA and only three with whitefish mtDNA. Hybrids and backcrosses had intermediate morphology and niche utilization compared to parental species. No evidence of selection against hybrids or backcrosses was apparent, as both hybrid and backcross growth rates and fecundities were high. Hybrids (F1) were only detected in two year-classes, suggesting temporal variability in mating between vendace and whitefish. However, our data show that hybrids reached sexual maturity and reproduced actively, with backcrosses recorded from six consecutive year-classes, whereas no F2 individuals were found. The results indicate widespread introgression, as 10.8% of coregonids were estimated to be backcrosses.

物种引入被认为是通过与本地动物群产生生态相互作用及遗传融合，进而导致生物多样性丧失的主要驱动因素之一。本研究选取单一湖泊中的两种公认鱼类——本土白鲑（whitefish, Coregonus lavaretus）与引入的湖白鲑（vendace, C. albula），以及二者的形态杂交个体，旨在检验野外环境中针对杂交个体与回交个体的选择淘汰作用。我们从白鲑属鱼类的总捕获样品中，随机抽取了具有代表性的693个个体，占总捕获量的27.8%。对该子样本进行筛选后，最终选取约50个纯本土白鲑（n=52）、纯湖白鲑（n=55）以及疑似杂交个体（n=19）用于遗传分析。后续的微卫星标记（microsatellites）与线粒体（mt）DNA分析，为杂交事件与基因渐渗提供了确凿的证据。在检测的126尾鱼类中，共发现4尾F1代杂交个体、14尾回交到本土白鲑的回交个体，以及7尾回交到湖白鲑的回交个体。历史基因流估算结果显示，引入的湖白鲑向本土白鲑的基因流动速率高于反向流动；而当代基因流的估算结果则显示二者速率相等。线粒体基因渐渗存在偏倚：18尾回交个体携带湖白鲑的线粒体DNA，仅3尾回交个体携带本土白鲑的线粒体DNA。与亲本物种相比，杂交个体及回交个体的形态特征与生态位利用均处于中间状态。未发现针对杂交个体或回交个体的选择淘汰迹象，杂交个体与回交个体的生长速率及繁殖力均处于较高水平。F1代杂交个体仅在两个同龄组中被检测到，这表明湖白鲑与本土白鲑的交配存在时间异质性。但本研究数据显示，杂交个体可达到性成熟并积极繁殖：回交个体在连续六个同龄组中均有记录，然而未发现F2代个体。研究结果表明基因渐渗现象广泛存在，据估算有10.8%的白鲑属鱼类个体为回交个体。