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.物种引入被视为通过与本地动物群产生生态相互作用及遗传融合，进而引发生物多样性丧失的主要驱动因素之一。本研究以单一天然湖泊中的两种广为人知的鱼类为研究对象：本土白鲑（Coregonus lavaretus，whitefish）与引入的欧白鲑（C. albula，vendace），同时纳入二者的形态杂交个体，旨在检测野外环境下针对杂交个体及回交个体的选择压力。我们从白鲑属鱼类的总捕捞样本中抽取693尾个体作为代表性随机子样本，占总捕捞量的27.8%。该子样本经筛选后，选取约50尾个体用于遗传分析，其中纯种白鲑52尾、纯种欧白鲑55尾、疑似杂交个体19尾。后续的微卫星（microsatellites）标记与线粒体（mt）DNA分析为杂交现象及基因渐渗提供了确凿证据。在所检测的126尾鱼类中，4尾为F1杂交个体，14尾为回交于白鲑的回交个体，7尾为回交于欧白鲑的回交个体。历史基因流估算结果显示，引入的欧白鲑向本土白鲑的基因交流速率高于反向交流；而当代基因流估算结果则显示二者速率相当。线粒体基因渐渗存在偏倚：18尾回交个体携带欧白鲑的线粒体DNA，仅3尾携带本土白鲑的线粒体DNA。杂交个体与回交个体的形态及生态位利用模式均介于两个亲本物种之间。未检测到针对杂交个体或回交个体的选择淘汰迹象，因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。仅在两个年群中检测到F1杂交个体，这表明欧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主动繁殖，回交个体在连续6个年群中均有检出，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%的白鲑属个体为回交个体。