Data from: Polymorphism at the Clock gene predicts phenology of long-distance migration in birds

Dissecting phenotypic variance in life history traits into its genetic and environmental components is at the focus of evolutionary studies and of pivotal importance to identify the mechanisms and predict the consequences of human-driven environmental change. The timing of recurrent life history events (phenology) is under strong selection, but the study of the genes that control potential environmental canalization in phenological traits is at its infancy. Candidate genes for circadian behaviour entrained by photoperiod have been screened as potential controllers of phenological variation of breeding and moult in birds, with inconsistent results. Despite photoperiodic control of migration is well established, no study has reported on migration phenology in relation to polymorphism at candidate genes in birds. We analysed variation in spring migration dates within four trans-Saharan migratory species (Luscinia megarhynchos; Ficedula hypoleuca; Anthus trivialis; Saxicola rubetra) at a Mediterranean island in relation to Clock and Adcyap1 polymorphism. Individuals with larger number of glutamine residues in the poly-Q region of Clock gene migrated significantly later in one or, respectively, two species depending on sex and whether the within-individual mean length or the length of the longer Clock allele was considered. The results hinted at dominance of the longer Clock allele. No significant evidence for migration date to covary with Adcyap1 polymorphism emerged. This is the first evidence that migration phenology is associated with Clock in birds. This finding is important for evolutionary studies of migration and sheds light on the mechanisms that drive bird phenological changes and population trends in response to climate change.

将生活史性状（life history traits）的表型方差（phenotypic variance）分解为遗传与环境组分，是进化生物学研究的核心议题，同时对阐明人类活动驱动的环境变化的作用机制、预测其影响具有关键意义。周期性生活史事件的发生时间即物候（phenology）受到强烈的选择压，但针对物候性状潜在环境缓冲（environmental canalization）调控机制的基因研究尚处于起步阶段。此前针对光周期介导的昼夜节律行为候选基因，已开展了鸟类繁殖与换羽物候变异潜在调控因子的筛选工作，但所得结果并不一致。尽管迁徙的光周期调控机制已得到充分证实，但目前尚无研究探讨鸟类迁徙物候与候选基因多态性之间的关联。我们以地中海一座岛屿为研究地点，对4种跨撒哈拉迁徙鸟类——Luscinia megarhynchos、Ficedula hypoleuca、Anthus trivialis、Saxicola rubetra——的春季迁徙日期变异展开分析，探讨其与Clock基因及Adcyap1基因多态性的关联。研究发现，在Clock基因的多聚谷氨酰胺（poly-Q）区域中，谷氨酰胺残基数量更多的个体，其迁徙时间显著更晚；这一效应在1个物种中单独显现，在另外2个物种中则受性别以及分析时采用个体内平均等位基因长度还是更长等位基因长度的影响而存在差异。研究结果暗示Clock基因的更长等位基因存在显性效应。未发现迁徙日期与Adcyap1基因多态性存在显著协同变异的证据。本研究首次证实鸟类迁徙物候与Clock基因存在关联。这一发现对于迁徙行为的进化生物学研究具有重要价值，同时为阐明气候变化背景下鸟类物候变化及种群动态变化的驱动机制提供了新的见解。