On the causes of geographically heterogeneous parallel evolution in sticklebacks
On the causes of geographically heterogeneous parallel evolution in sticklebacks
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DOI：
10.1038/s41559-020-1222-6
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发表时间：
2020-06-22
影响因子：
16.8
通讯作者：
Merila, Juha
中科院分区：
文献类型：
--
作者：
Fang, Bohao;Kemppainen, Petri;Merila, Juha
三棘棘鱼（Gasterosteus aculeatus）是研究野外平行进化的重要模式系统，在整个北半球的海洋中反复定居和适应淡水。以前的研究确定了许多基因组区域，在淡水生态型和海洋生态型之间显示出一致的遗传差异，但这些研究通常具有有限的地理采样，并且主要集中在东太平洋地区。我们分析了全球三刺鱼海洋和淡水生态型样本的种群基因组数据，以检测不同地理尺度上参与平行进化的位点。平行进化的大多数特征是东太平洋独有的，跨洋海洋-淡水分化仅限于有限数量的共享基因组区域，包括三个染色体倒位。在模拟和经验数据的基础上，我们证明了这可能是由于大西洋盆地入侵期间淡水适应等位基因的随机丢失和海洋中淡水适应变异的选择，这两者都可以减少东太平洋地区以外淡水适应的现有遗传变异。此外，东太平洋与海洋-淡水分化相关的联系不平衡加剧与过去冰期海洋和淡水种群之间的二次接触是一致的，这些种群在相互隔离的情况下进化。因此，与早期在东太平洋地区的研究让我们相信的相反，刺鱼的平行海洋-淡水分化在物种全球分布范围的所有其他地区都远没有那么普遍和明显。来自全球三刺鱼数据集的种群基因组数据显示，海洋与淡水分化的平行特征比之前认为的要少。
The three-spined stickleback (Gasterosteus aculeatus) is an important model system for the study of parallel evolution in the wild, having repeatedly colonized and adapted to freshwater from the sea throughout the northern hemisphere. Previous studies identified numerous genomic regions showing consistent genetic differentiation between freshwater and marine ecotypes but these had typically limited geographic sampling and mostly focused on the Eastern Pacific region. We analysed population genomic data from global samples of the three-spined stickleback marine and freshwater ecotypes to detect loci involved in parallel evolution at different geographic scales. Most signatures of parallel evolution were unique to the Eastern Pacific and trans-oceanic marine-freshwater differentiation was restricted to a limited number of shared genomic regions, including three chromosomal inversions. On the basis of simulations and empirical data, we demonstrate that this could result from the stochastic loss of freshwater-adapted alleles during the invasion of the Atlantic basin and selection against freshwater-adapted variants in the sea, both of which can reduce standing genetic variation available for freshwater adaptation outside the Eastern Pacific region. Moreover, the elevated linkage disequilibrium associated with marine-freshwater differentiation in the Eastern Pacific is consistent with secondary contact between marine and freshwater populations that evolved in isolation from each other during past glacial periods. Thus, contrary to what earlier studies from the Eastern Pacific region have led us to believe, parallel marine-freshwater differentiation in sticklebacks is far less prevalent and pronounced in all other parts of the species global distribution range.Population genomic data from a global dataset of three-spined sticklebacks show that parallel signatures of marine to freshwater differentiation are less common than previously thought.