Data from: Strong survival selection on seasonal migration versus residence induced by extreme climatic events

1. Elucidating the full eco-evolutionary consequences of climate change requires quantifying the impact of extreme climatic events (ECEs) on selective landscapes of key phenotypic traits that mediate responses to changing environments. Episodes of strong ECE-induced selection could directly alter population composition, and potentially drive micro-evolution. However, to date, few studies have quantified ECE-induced selection on key traits, meaning that immediate and longer-term eco-evolutionary implications cannot yet be considered. 2. One widely-expressed trait that allows individuals to respond to changing seasonal environments, and directly shapes spatio-seasonal population dynamics, is seasonal migration versus residence. Many populations show considerable among-individual phenotypic variation, resulting in 'partial migration'. However, variation in the magnitude of direct survival selection on migration versus residence has not been rigorously quantified, and empirical evidence of whether seasonal ECEs induce, intensify, weaken or reverse such selection is lacking. 3. We designed full-annual-cycle multi-state capture-recapture models that allow estimation of seasonal survival probabilities of migrants and residents from spatio-temporally heterogeneous individual resightings. We fitted these models to nine years of geographically extensive year-round resighting data from partially migratory European shags (Phalacrocorax aristotelis). We thereby quantified seasonal and annual survival selection on migration versus residence across benign and historically extreme non-breeding season (winter) conditions, and tested whether selection differed between females and males. 4. We show that two of four observed ECEs, defined as severe winter storms causing overall low survival, were associated with very strong seasonal survival selection against residence. These episodes dwarfed the weak selection or neutrality evident otherwise, and hence caused selection through overall annual survival. The ECE that caused highest overall mortality and strongest selection also caused sex-biased mortality, but there was little overall evidence of sex-biased selection on migration versus residence. 5. Our results imply that seasonal ECEs and associated mortality can substantially shape the landscape of survival selection on migration versus residence. Such ECE-induced phenotypic selection will directly alter migrant and resident frequencies, and thereby alter immediate spatio-seasonal population dynamics. Given underlying additive genetic variation, such ECEs could potentially cause micro-evolutionary changes in seasonal migration, and thereby cause complex eco-evolutionary population responses to changing seasonal environments.

1. 阐明气候变化的完整生态进化效应，需量化极端气候事件（extreme climatic events, ECEs）对介导环境变化响应的关键表型性状（phenotypic traits）的选择景观所产生的影响。高强度极端气候事件诱发的选择事件可直接改变种群组成，并有可能推动微进化（micro-evolution）进程。然而，截至目前，鲜有研究针对关键性状量化极端气候事件诱发的选择作用，致使我们尚无法评估其即时与长期的生态进化后果。
2. 允许个体响应季节性环境变化、并直接塑造时空季节性种群动态的一类广泛表达的性状，是季节性迁徙与居留策略。许多种群存在显著的个体间表型变异，进而形成‘部分迁徙（partial migration）’现象。然而，针对迁徙与居留策略的直接生存选择（survival selection）强度的变异尚未得到严格量化，且尚缺乏经验证据表明季节性极端气候事件会诱发、强化、削弱还是逆转这类选择作用。
3. 我们构建了全年度周期多状态标记重捕模型（capture-recapture models），可基于时空异质性的个体重识别数据估算迁徙者与居留者的季节性生存概率。我们将该模型应用于来自部分迁徙性物种欧洲鸬鹚（Phalacrocorax aristotelis）的9年、地理覆盖范围广泛的全年重识别数据集。借此，我们量化了在温和与历史极端非繁殖季（冬季）条件下，迁徙与居留策略所对应的季节性及年度生存选择，并检验了雌雄个体间的选择差异。
4. 研究结果显示，在4次观测到的极端气候事件中，有2次被定义为引发整体低存活率的严重冬季风暴，其与针对居留策略的极强季节性生存选择显著相关。这类事件远超其余场景下的弱选择或中性状态，并通过整体年度存活率产生选择作用。引发最高整体死亡率与最强选择的极端气候事件同时造成了性别偏向性死亡，但几乎没有整体证据表明迁徙与居留策略上存在性别偏向性选择。
5. 我们的研究结果表明，季节性极端气候事件及其伴随的死亡率可显著塑造迁徙与居留策略相关的生存选择景观。这类由极端气候事件诱发的表型选择可直接改变迁徙者与居留者的种群频率，进而改变即时的时空季节性种群动态。考虑到潜在的加性遗传变异，这类极端气候事件有可能引发季节性迁徙的微进化改变，进而导致种群对季节性环境变化产生复杂的生态进化种群响应。