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.

阐明合子后生殖隔离（postzygotic reproductive isolation）背后的表型基础，对全面解析物种的演化与维持机制至关重要。此前极少被探究的一类合子后生殖隔离障碍，便是杂交个体的学习与记忆能力。学习与记忆属于重要的适合度相关性状（fitness-related traits），在分散贮食（scatter-hoarding）物种中尤为如此——精准找回贮藏的食物是其越冬存活的关键。本研究以两种分散贮食鸣禽——黑头山雀（Poecile atricapillus）与卡罗莱纳山雀（Poecile carolinensis）及其天然杂交种为研究材料，通过比较三者的学习记忆性状，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。在室外鸟舍环境下的实验结果显示，相较于两个亲本物种，杂交山雀在联想学习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类物种间合子后生殖隔离的促成因素之一。鉴于学习与记忆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发挥了关键却迄今未被关注的作用。