Data from: Hybrid chickadees are deficient in learning and memory

Identifying the phenotypes underlying postzygotic reproductive isolation is crucial for fully understanding the evolution and maintenance of species. One potential postzygotic isolating barrier that has rarely been examined is learning and memory ability in hybrids. Learning and memory are important fitness-related traits, especially in scatter-hoarding species, where accurate retrieval of hoarded food is vital for winter survival. Here, we test the hypothesis that learning and memory ability can act as a postzygotic isolating barrier by comparing these traits among two scatter-hoarding songbird species, black-capped (Poecile atricapillus), Carolina chickadees (Poecile carolinensis), and their naturally occurring hybrids. In an outdoor aviary setting, we find that hybrid chickadees perform significantly worse on an associative learning spatial task and are worse at solving a novel problem compared to both parental species. Deficiencies in learning and memory abilities could therefore contribute to postzygotic reproductive isolation between chickadee species. Given the importance of learning and memory for fitness, our results suggest that these traits may play an important, but as yet overlooked, role in postzygotic reproductive isolation.明确合子后生殖隔离（postzygotic reproductive isolation）背后的表型基础，对于全面理解物种的演化与维持至关重要。目前极少被探究的合子后生殖隔离障碍之一，便是杂交个体的学习与记忆能力。学习与记忆是与适合度（fitness）密切相关的重要性状，在分散贮食（scatter-hoarding）物种中尤为关键——这类物种精准取回贮藏食物的能力是其冬季存活的核心保障。本研究以两种分散贮食鸣禽：黑头山雀（Poecile atricapillus）、卡罗莱纳山雀（Poecile carolinensis）及其自然杂交后代为研究对象，通过比较三者的学习与记忆相关性状，验证"学习与记忆能力可作为合子后生殖隔离障碍"这一假说。在室外鸟舍环境中，我们发现相较于两个亲本物种，杂交山雀在联想学习（associative learning）空间任务中的表现显著更差，且解决全新问题的能力也更为薄弱。由此可见，学习与记忆能力的缺陷可能是山雀物种间合子后生殖隔离的重要成因之一。鉴于学习与记忆能力对物种适合度的重要意义，本研究结果表明，这类性状可能在合子后生殖隔离中扮演了长期被忽视的关键角色。