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.

长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，改善社会单配制动物的繁殖表现。然而，由于年龄与繁殖经验等关键混杂因素的存在，对此开展严谨的实证检验一直极具挑战。本研究弥补了既往研究的不足，针对社会单配制的蓝脚鲣鸟（Sula nebouxii）——一种长寿且离异率较高的海洋鸟类——的配偶熟悉度效应开展了严格检验。本研究利用该物种年龄与配偶关系时长间天然的解耦现象，并针对24年的数据库采用全新的分析方法，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体可在繁殖季提前5周启动产卵，卵的孵化率更高，且能多抚育35%的幼鸟成功离巢。本研究结果证实，配偶关系时长可提升个体适合度，并进一步表明，雌雄个体行为间的协同效应或在配偶熟悉度效应的产生中发挥了关键作用。这些发现有助于解释重新配对所带来的、不受年龄与经验影响的繁殖收益，及其在生活史演化中的作用。