Département de biologie, Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, G1V 0A6 Québec, Canada.
Evolution. 2018 Jun;72(6):1261-1277. doi: 10.1111/evo.13486.
Understanding the dual roles of demographic and selective processes in the buildup of population divergence is one of the most challenging tasks in evolutionary biology. Here, we investigated the demographic history of Atlantic salmon across the entire species range using 2035 anadromous individuals from North America and Eurasia. By combining results from admixture graphs, geo-genetic maps, and an Approximate Bayesian Computation (ABC) framework, we validated previous hypotheses pertaining to secondary contact between European and Northern American populations, but also identified secondary contacts in European populations from different glacial refugia. We further identified the major sources of admixture from the southern range of North America into more northern populations along with a strong signal of secondary gene flow between genetic regional groups. We hypothesize that these patterns reflect the spatial redistribution of ancestral variation across the entire North American range. Results also support a role for linked selection and differential introgression that likely played an underappreciated role in shaping the genomic landscape of species in the Northern hemisphere. We conclude that studies between partially isolated populations should systematically include heterogeneity in selective and introgressive effects among loci to perform more rigorous demographic inferences of the divergence process.
理解人口和选择过程在种群分歧形成中的双重作用是进化生物学中最具挑战性的任务之一。在这里，我们利用来自北美洲和欧亚大陆的 2035 个洄游个体，研究了大西洋鲑在整个物种范围内的种群历史。通过结合混合图、地理遗传图谱和近似贝叶斯计算（ABC）框架的结果，我们验证了先前关于欧洲和北美种群之间二次接触的假设，但也在来自不同冰川避难所的欧洲种群中发现了二次接触。我们进一步确定了从北美南部到更北部种群的混合的主要来源，以及遗传区域群体之间强烈的次级基因流信号。我们假设这些模式反映了祖先变异在整个北美范围内的空间再分配。研究结果还支持连锁选择和差异渐渗的作用，这可能在塑造北半球物种的基因组景观方面发挥了被低估的作用。我们得出结论，在部分隔离的种群之间进行的研究应系统地包括各基因座选择和渐渗作用的异质性，以对分歧过程进行更严格的人口推断。
