Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada.
Department of Environment, Fish and Wildlife Division, Government of Yukon, Whitehorse, Yukon, Canada.
Mol Ecol. 2023 Jun;32(12):3025-3043. doi: 10.1111/mec.16913. Epub 2023 Apr 3.
Polymorphic species are useful models for investigating the evolutionary processes driving diversification. Such processes include colonization history as well as contemporary selection, gene flow, and genetic drift, which can vary between intraspecific morphs as a function of their distinct life histories. The interactive and relative influence of such evolutionary processes on morph differentiation critically informs morph-specific management decisions and our understanding of incipient speciation. We therefore investigated how geographic distance, environmental conditions, and colonization history interacted with morph migratory capacity in the highly polymorphic fish species, Arctic Charr (Salvelinus alpinus). Using an 87 k SNP chip we genetically characterized recently evolved anadromous, resident, and landlocked charr collected from 45 locations across a secondary contact zone of three charr glacial lineages in eastern Canada. A strong pattern of isolation by distance across all populations suggested geographic distance principally shaped genetic structure. Landlocked populations had lower genetic diversities and higher genetic differentiation than anadromous populations. However, effective population size was generally temporally stable in landlocked populations in comparison to anadromous populations. Genetic diversity positively correlated with latitude, potentially indicating southern anadromous populations' vulnerability to climate change and greater introgression between the Arctic and Atlantic glacial lineages in northern Labrador. Local adaptation was suggested by the observation of several environmental variables strongly associating with functionally relevant outlier genes including a region on chromosome AC21 potentially associated with anadromy. Our results demonstrate that gene flow, colonization history, and local adaptation uniquely interact to influence the genetic variation and evolutionary trajectory of populations.
多态种是研究驱动多样化的进化过程的有用模型。这些过程包括殖民历史以及当代选择、基因流和遗传漂变，它们可以因不同生活史的种内形态而有所不同。这些进化过程的相互作用和相对影响对形态分化的形态特异性管理决策和我们对初期物种形成的理解至关重要。因此，我们调查了地理距离、环境条件和殖民历史如何与高度多态的鱼类——北极鳕鱼（Salvelinus alpinus）的形态迁徙能力相互作用。我们使用 87k SNP 芯片对来自加拿大东部三个鳕鱼冰川谱系的二次接触区的 45 个地点采集的最近进化的洄游型、定居型和陆封型鳕鱼进行了遗传特征分析。所有种群的隔离距离强烈模式表明地理距离主要塑造了遗传结构。与洄游型种群相比，陆封型种群的遗传多样性较低，遗传分化程度较高。然而，与洄游型种群相比，陆封型种群的有效种群大小通常在时间上较为稳定。遗传多样性与纬度呈正相关，这可能表明南部洄游种群对气候变化的脆弱性更大，以及在拉布拉多北部的北极和大西洋冰川谱系之间的基因渗入更多。观察到几个环境变量与功能相关的异常基因强烈相关，包括可能与洄游性相关的染色体 AC21 上的一个区域，这表明存在局部适应。我们的研究结果表明，基因流、殖民历史和局部适应独特地相互作用，影响种群的遗传变异和进化轨迹。
