Kilpisjärvi Biological Station, University of Helsinki, Käsivarrentie 14622, FI-99490 Kilpisjärvi, Finland.
Mol Ecol. 2011 Sep;20(18):3838-55. doi: 10.1111/j.1365-294X.2011.05209.x. Epub 2011 Aug 10.
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 (Coregonus 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 c. 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 F(1) , 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 with parental species. No evidence of selection against hybrids or backcrosses was apparent, as both hybrid and backcross growth rates and fecundities were high. Hybrids (F(1) ) were only detected in 2 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 F(2) 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生态相互作用和与当地动物区系的基因混合导致生物多样性丧失的主要驱动因素之一。我们检查了两个公认的鱼类物种，本地白鲑（Coregonus lavaretus）和引入的白鲑（Coregonus albula），以及它们在单个湖泊中的形态杂种，以测试野外对杂种和回交的选择。从总捕捞的核心鱼类中随机抽取了代表随机亚样本 693 个个体（27.8%）。该亚样本被检查，目的是选择约 50 个纯白鲑（n = 52）、纯白鲑（n = 55）和假定杂种（n = 19）个体进行遗传分析。随后的微卫星和线粒体（mt）DNA 分析提供了杂交和基因渗入的有力证据。在所检查的 126 条鱼中，发现了 4 条是 F1，14 条回交至白鲑，7 条回交至白鲑。历史基因流的估计表明，从引入的白鲑到本地白鲑的基因流高于反之亦然，而当代基因流的估计则相等。线粒体基因渗入存在偏倚，有 18 条回交具有白鲑 mtDNA，只有 3 条具有白鲑 mtDNA。杂种和回交的形态和生态位利用处于中间状态，与亲本物种相比。没有明显的选择对杂种或回交的证据，因为杂种和回交的生长率和繁殖力都很高。杂种（F1）仅在 2 个年龄组中检测到，表明白鲑和白鲑之间的交配存在时间变异性。然而，我们的数据表明，杂种达到了性成熟并积极繁殖，记录到 6 个连续的年龄组中有回交，而没有发现 F2 个体。结果表明广泛的基因渗入，估计有 10.8%的核心鱼类是回交。
