Dataset from: Differential epigenetic regulation underlies evolutionary transition of seasonal migration

Seasonal migratory animals can evolve residency through adaptation. The threshold model of quantitative genetics predicts that residency evolves from migrants when genetic variation for lower liability, or a latent state underlying migratory propensity, is positively selected. However, it is unknown what cellular and molecular regulations underlie this process. The hypothalamus, which regulates physiology and behaviour of vertebrates by integrating internal and environmental conditions, is a strong candidate structure where migratory propensity may be regulated. To understand the hypothalamic molecular regulation underlying the evolutionary change to residency, we use the Eurasian blackcap system comprising ancestral migratory and derived resident populations. By combining a common-garden experiment with single cell epigenetics, we compare genomic regions with open chromatin between migratory and resident populations and seasons. We find that the seasonal change in chromatin accessibility is reduced in residents across major cell types. This suggests that the evolutionary transition to residency involves a reduction in the amplitude of seasonal change in epigenetic states in multiple hypothalamic cell types, which may collectively represent migratory liability. Environmental shifts, such as deglaciation for blackcaps, may play an important role in exposing and selecting variation in the seasonal reaction norm of liability underlying evolution of seasonal plastic traits.季节性迁徙动物可通过适应性演化获得定居习性。数量遗传学（quantitative genetics）阈值模型预测：当降低迁徙易感性（即支撑迁徙倾向的潜在状态）的遗传变异受到正向选择时，迁徙种群可演化出定居习性。但目前尚不明确支撑这一演化过程的细胞与分子调控机制。下丘脑（hypothalamus）作为脊椎动物通过整合内外部环境条件调控生理与行为的中枢脑区，是调控迁徙倾向的关键候选结构。为解析定居性演化过程中下丘脑的分子调控机制，本研究采用兼具祖先迁徙种群与衍生定居种群的欧亚黑顶林莺（Eurasian blackcap）作为研究模型。本研究结合同质饲养实验（common-garden experiment）与单细胞表观遗传学（single cell epigenetics）技术，对比迁徙种群与定居种群在不同季节间的开放染色质（open chromatin）基因组区域差异。研究发现，在主要下丘脑细胞类群中，定居种群的染色质可及性季节性变化幅度显著降低。这表明，向定居性的演化转变涉及多个下丘脑细胞类群中表观遗传状态季节性变化幅度的衰减，该变化或共同构成迁徙易感性的基础。环境变迁（如黑顶林莺所经历的冰期消退）或在暴露并选择季节性可塑性性状演化背后的易感性季节性反应规范变异过程中发挥关键作用。