Data from: Better stay together: pair bond duration increases individual fitness independent of age-related variation

Prolonged pair bonds have the potential to improve reproductive performance of socially monogamous animals by increasing pair familiarity and enhancing coordination and cooperation between pair members. However, this has proved very difficult to test robustly because of important confounds such as age and reproductive experience. Here, we address limitations of previous studies and provide a rigorous test of the mate familiarity effect in the socially monogamous blue-footed booby, Sula nebouxii, a long-lived marine bird with a high divorce rate. Taking advantage of a natural disassociation between age and pair bond duration in this species, and applying a novel analytical approach to a 24 year database, we found that those pairs which have been together for longer establish their clutches five weeks earlier in the season, hatch more of their eggs and produce 35% more fledglings, regardless of age and reproductive experience. Our results demonstrate that pair bond duration increases individual fitness and further suggest that synergistic effects between a male and female's behaviour are likely to be involved in generating a mate familiarity effect. These findings help to explain the age- and experience-independent benefits of remating and their role in life-history evolution.

持久的配偶纽带可通过提升配偶间熟悉度、强化配对双方的协调与合作，提升社会性一夫一妻制动物的繁殖表现。然而，受限于年龄、繁殖经验等关键混杂因素，该假说的稳健检验长期以来极具挑战。本研究针对既往研究的局限进行改进，以社会性一夫一妻制的蓝脚鲣鸟（Sula nebouxii）——一种长寿且离异率较高的海洋鸟类——为研究对象，对配偶熟悉度效应开展严谨检验。本研究利用该物种中年龄与配偶纽带时长天然解离的特性，并针对24年的长期观测数据库采用新颖的分析方法，结果发现：无论个体年龄与繁殖经验如何，配对时长更长的配偶群均能在繁殖季提早5周完成产卵、孵化更多卵，且成功出飞的幼鸟数量提升35%。本研究结果证实，配偶纽带时长可提升个体适合度，并进一步提示：雌雄个体行为间的协同效应，或是配偶熟悉度效应产生的潜在机制。这些发现有助于阐释重新配对所带来的、不受年龄与繁殖经验影响的繁殖收益，及其在生活史进化中的作用。