Data from: Secondary contact and changes in coastal hydrology influence the nonequilibrium population structure of a salmonid (Oncorhynchus keta)

Numerous empirical studies have reported lack of migration–drift equilibrium in wild populations. Determining the causes of nonequilibrium population structure is challenging because different evolutionary processes acting at a variety of spatiotemporal scales can produce similar patterns. Studies of contemporary populations in northern latitudes suggest that nonequilibrium population structure is probably caused by recent colonization of the region after the last Pleistocene ice age ended ~13 000 years ago. The chum salmon's (Oncorhynchus keta) range was fragmented by dramatic environmental changes during the Pleistocene. We investigated the population structure of chum salmon on the North Alaska Peninsula (NAP) and, using both empirical data and simulations, evaluated the effects of colonization timing and founder population heterogeneity on patterns of genetic differentiation. We screened 161 single nucleotide polymorphisms and found evidence of nonequilibrium population structure when the slope of the isolation-by-distance relationship was examined at incremental spatial scales. In addition, simulations suggested that this pattern closely matched models of recent colonization of the NAP by secondary contact. Our results agree with geological and archaeological data indicating that the NAP was a dynamic landscape that may have been more recently colonized than during the last deglaciation because of dramatic changes in coastal hydrology over the last several thousand years.

多项实证研究均证实，野生种群普遍存在迁移-漂变平衡（migration–drift equilibrium）缺失的现象。解析种群结构非平衡状态的成因极具挑战性，因为不同时空尺度下的多种进化过程均可产生相似的种群格局。针对高纬度地区现存种群的研究显示，这类非平衡种群结构大概率源于末次冰期（约1.3万年前结束）后该区域的新近定居事件。大麻哈鱼（Oncorhynchus keta）的分布范围在更新世时期因剧烈的环境变化而发生破碎化。本研究以阿拉斯加北半岛（North Alaska Peninsula, NAP）的大麻哈鱼种群为研究对象，对其种群结构展开探究，并结合实证数据与模拟实验，评估了定居时间与奠基种群异质性对遗传分化格局的影响。本研究筛选得到161个单核苷酸多态性（single nucleotide polymorphisms, SNP）位点，当在递进空间尺度下分析距离隔离（isolation-by-distance）关系的斜率时，发现了非平衡种群结构的相关证据。此外，模拟实验结果表明，该种群格局与通过二次接触新近定居阿拉斯加北半岛的模型高度吻合。本研究结果与地质学及考古学数据相一致：相关数据表明，阿拉斯加北半岛曾是动态变化的景观，由于近数千年来沿海水文的剧烈变化，该区域的定居时间可能晚于末次冰消期。