Data from: Genetic signs of multiple colonization events in Baltic ciscoes with radiation into sympatric spring and autumn-spawners confined to early post-glacial arrival

Presence of sympatric populations may reflect local diversification or secondary contact of already distinct forms. The Baltic cisco (Coregonus albula) normally spawns in late autumn, but in a few lakes in Northern Europe sympatric autumn and spring- or winter-spawners have been described. So far, the evolutionary relationships and taxonomic status of these main life history forms have remained largely unclear. With microsatellites and mtDNA sequences, we analyzed extant and extinct spring- and autumn-spawners from a total of 23 Swedish localities, including sympatric populations. Published sequences from Baltic ciscoes in Germany and Finland, and Coregonus sardinella from North America were also included together with novel mtDNA sequences from Siberian C. sardinella. A clear genetic structure within Sweden was found that included two population assemblages markedly differentiated at microsatellites and apparently fixed for mtDNA haplotypes from two distinct clades. All sympatric Swedish populations belonged to the same assemblage, suggesting parallel evolution of spring-spawning rather than secondary contact. The pattern observed further suggests that postglacial immigration to Northern Europe occurred from at least two different refugia. Previous results showing that mtDNA in Baltic cisco is paraphyletic with respect to North American C. sardinella were confirmed. However, the inclusion of Siberian C. sardinella revealed a more complicated pattern, as these novel haplotypes were found within one of the two main C. albula clades and were clearly distinct from those in North American C. sardinella. The evolutionary history of Northern Hemisphere ciscoes thus seems to be more complex than previously recognized.

同域种群（sympatric populations）的存在，可反映类群的本地分化或是已分化类群间的二次接触。波罗的海白鲑（Baltic cisco，Coregonus albula）通常于晚秋产卵，但北欧少数湖泊中已报道存在同域分布的秋季产卵型与春季/冬季产卵型种群。迄今为止，这类主要生活史类型的演化关系与分类地位仍未完全明晰。本研究借助微卫星（microsatellites）与线粒体DNA序列（mtDNA sequences），对瑞典境内23个采样点（涵盖同域种群）的现存与已灭绝的春季、秋季产卵型个体进行了分析。同时纳入了德国、芬兰波罗的海白鲑的已发表序列、北美西鲱白鲑（Coregonus sardinella）的相关序列，并补充了西伯利亚西鲱白鲑的全新线粒体DNA序列。研究在瑞典境内的白鲑种群中发现了清晰的遗传结构：存在两个在微卫星位点上显著分化的种群集群，且二者分别固定携带两个不同演化支（clades）的线粒体DNA单倍型（mtDNA haplotypes）。所有瑞典境内的同域种群均隶属于同一集群，这表明春季产卵型类群的起源更倾向于平行演化，而非二次接触。该观测结果还提示，北欧种群的冰期后迁入至少来自两个不同的避难所（refugia）。本研究证实了此前的结论：波罗的海白鲑的线粒体DNA相较于北美西鲱白鲑属于并系类群（paraphyletic）。但纳入西伯利亚西鲱白鲑序列后，我们发现了更为复杂的演化模式——这些新增的单倍型被归入两个主要C. albula演化支中的一支，且与北美西鲱白鲑的单倍型存在显著差异。综上，北半球白鲑类群的演化历史比此前认知的更为复杂。