Abstract Animals inhabiting montane gradients experience varying winter climates that may result in differential selection on survival-related traits. Higher elevations in temperate climates are characterized by harsher winters with greater and longer-lasting snow cover compared to lower elevations, potentially leading to stronger selection for traits that improve fitness under these harsher conditions. For food-caching mountain chickadees, Poecile gambeli , inhabiting harsh high elevation environments, individual variation in spatial cognitive abilities related to cache retrieval is associated with significant differences in overwinter survival. Compared to lower elevations, stronger predicted selection on traits needed for overwinter survival at higher elevations can be expected to result in higher adult annual survival despite harsher environmental conditions, indicating that individuals that survive their first winter are better suited to survive similar subsequent selection events. Here, we used a Bayesian hierarchical Cormack-Jolly-Seber (CJS) model to estimate and compare survival of adult mountain chickadees at higher and lower elevations over 3 years. We showed that adult survival was consistently higher at higher elevations despite much harsher environmental conditions, supporting our hypothesis that selection on overwinter survival-related traits (such as spatial cognition) is stronger at our high elevation study area than at lower elevations. Significance statement Understanding how environmental conditions are associated with different selection strengths on survival-related traits is an important question in behavioral ecology. Directly estimating differences in strength of selection is daunting, but comparing survival between environments may provide an alternative method. We tested for differences in adult survival in a resident food-caching species at higher and lower elevations varying in winter climate severity. These birds rely on food caches for winter survival, and juvenile birds with better spatial cognition (needed for cache retrieval) have higher survival during their first year at higher harsher elevations. Here, we report higher adult survival at higher elevations compared to lower elevations, despite much harsher winter environment. Such findings support our hypothesis for stronger selection in harsher winter conditions because individuals that survive their first year under stronger selection are better suited to survive subsequent selection events.

中文翻译：

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成年食物缓存山雀的年生存率与海拔相关的差异与空间认知的自然选择一致

摘要 栖息在山地梯度的动物会经历不同的冬季气候，这可能会导致对生存相关性状的不同选择。与低海拔地区相比，温带气候中海拔较高的地区冬季更严酷，积雪覆盖更广、持续时间更长，这可能会导致在这些更恶劣的条件下更好地选择能够改善健康状况的性状。对于食物缓存山山雀，Poecile gambeli 居住在恶劣的高海拔环境中，与缓存检索相关的空间认知能力的个体差异与越冬生存的显着差异有关。与低海拔相比，尽管环境条件更严酷，但对在高海拔地区越冬生存所需性状的更强预测选择预计会导致更高的成年年生存率，这表明在第一个冬天幸存下来的个体更适合在类似的后续选择事件中幸存下来。在这里，我们使用贝叶斯分层 Cormack-Jolly-Seber (CJS) 模型来估计和比较 3 年内在高海拔和低海拔地区成年山雀的存活率。我们表明，尽管环境条件更加恶劣，但海拔较高的成虫存活率始终较高，这支持了我们的假设，即在我们的高海拔研究区域，对越冬生存相关性状（例如空间认知）的选择比在低海拔地区更强。意义声明 了解环境条件如何与生存相关性状的不同选择强度相关联是行为生态学中的一个重要问题。直接估计选择强度的差异令人生畏，但比较环境之间的生存可能提供另一种方法。我们测试了在冬季气候严重程度不同的较高和较低海拔的常驻食物缓存物种的成虫存活率差异。这些鸟类依靠食物储藏室过冬，而具有更好空间认知能力（需要检索储藏室）的幼鸟在较高海拔的第一年有更高的存活率。在这里，我们报告了尽管冬季环境更加恶劣，但与低海拔地区相比，高海拔地区的成虫存活率更高。