Genetic relationships between sympatric and allopatric Coregonus ciscoes in North and Central Europe

Background
Sympatric speciation along ecological gradients has been studied repeatedly, in particular in freshwater fishes. Rapid post-glacial ecological divergence has resulted in numerous endemic species or ecologically distinct populations in lakes of the temperate zones. Here, we focus on the Baltic cisco (Coregonus albula) complex, to study the genetic similarity among two pairs of sympatric autumn- and spring-spawning populations from post-glacial German Lakes Stechlin and Breiter Luzin. For comparison, we included a similar pair of sympatric populations from the Swedish Lake Fegen. We wanted to explore potential genetic similarities between the three sympatric cisco population pairs in the three lakes, to evaluate whether the pairs may have emerged independently in the three lakes, or whether two different species may have colonized all three lakes independently. Furthermore, we considered allopatric C. albula populations from three Polish, three Finnish, and four Swedish locatio..., The dataset originates from merging previously published data from Swedish populations (Delling B, Palm S, Palkopoulou E, Prestegaard T. Genetic signs of multiple colonization events in Baltic ciscoes with radiation into sympatric spring- and autumn-spawners confined to early postglacial arrival. Ecol Evol 2014; 4(22):4346-4360.) with newly analysed data from German, Polish, Finnish and Russian populations. Because samples were analyzed on different sequencers, eight individuals were analysed on both sequencers. The systematic differences in read lengths per microsatellite between the sequencers were used to align the Swedish data to the new dataset, by adding the difference in read lengths to each sample from the Swedish data.
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研究背景
沿生态梯度的同域物种形成（sympatric speciation）已被广泛研究，尤以淡水鱼类类群为焦点。冰期后快速的生态分化，造就了温带区域湖泊中大量的特有物种与生态分化显著的种群。本研究聚焦波罗的海白鲑（Coregonus albula）复合体，针对德国施特希林湖与布赖特卢津湖这两处冰期后形成的湖泊中的两对同域秋季产卵与春季产卵种群，开展遗传相似性分析。为设置对照，本研究纳入瑞典费根湖中的一对类似同域种群。本研究旨在探索上述三个湖泊中的三对白鲑同域种群类群间的潜在遗传相似性，以评估这些种群类群究竟是在三个湖泊中独立形成，还是由两种不同物种分别独立定植了这三个湖泊。此外，本研究纳入了来自波兰、芬兰、瑞典的异域分布波罗的海白鲑（Coregonus albula）种群，其中波兰3个、芬兰3个、瑞典4个（原文此处未完整）。
本数据集整合了此前已发表的瑞典种群相关数据（Delling B, Palm S, Palkopoulou E, Prestegaard T. 波罗的海白鲑存在多次定植事件的遗传信号，且其辐射演化形成局限于冰期早期定植的同域春、秋季产卵类群. *Ecol Evol* 2014; 4(22):4346-4360.），以及新分析的德国、波兰、芬兰与俄罗斯种群数据。由于样本在不同测序仪上完成测序，其中有8个个体在两台测序仪上均进行了分析。研究人员利用不同测序仪间每个微卫星的读长系统差异，通过为瑞典数据集的每个样本添加读长差值的方式，将瑞典数据集校正后对齐至新数据集。
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