Data from: Morph-specific patterns of reproductive senescence: connections to discrete reproductive strategies

How reproductive strategies contribute to patterns of senescence in natural populations remains contentious. We studied reproductive senescence in the dimorphic white-throated sparrow, an excellent species for exploring this issue. Within both sexes the morphs use distinct reproductive strategies, and disassortative pairing by morph results in pair types with distinct parental systems. White morph birds are more colorful and aggressive than tan counterparts, and white males compete for extra-pair matings whereas tan males are more parental. Tan males and white females share parental care equally, whereas white males provide little parental support to tan females. We found morph-specific patterns of reproductive senescence in both sexes. White males exhibited greater reproductive senescence than tan males. This result likely reflects the difficulty of sustaining a highly competitive reproductive strategy as aging progresses, rather than high physiological costs of competitiveness, since white males were also long-lived. Moreover, morph was not consistently related to reproductive senescence across the sexes, arguing against especially high costs of the traits associated with white morph identity. Rather, tan females exhibited earlier reproductive senescence than white females, and were short-lived, perhaps reflecting the challenges of unsupported motherhood. Results underscore the importance of social dynamics in determining patterns of reproductive senescence.繁殖策略如何塑造自然种群的衰老模式，这一议题迄今仍存在较大争议。本研究以二态性白喉带鹀为研究对象，该物种是探讨该问题的理想实验类群。该物种雌雄个体均存在两种形态型（morph），不同形态型个体采用截然不同的繁殖策略；且形态型间的异型配对会形成具有独特育雏体系的配偶组合。白色形态型个体的羽色更为艳丽，攻击性亦强于黄褐色形态型个体：白色雄鸟会通过竞争获取额外配对交配（extra-pair matings）机会，而黄褐色雄鸟则更倾向于投入育雏行为。黄褐色雄鸟与白色雌鸟会均等分担育雏工作，而白色雄鸟几乎不会为黄褐色雌鸟提供育雏支持。本研究发现，雌雄个体均呈现出与形态型相关的繁殖衰老（reproductive senescence）模式。白色雄鸟的繁殖衰老程度显著高于黄褐色雄鸟。鉴于白色雄鸟本身寿命更长，该结果或反映出随着衰老进程推进，维持高竞争性繁殖策略的难度逐渐提升，而非竞争行为本身带来了高昂的生理代价。此外，形态型与繁殖衰老的关联在两性间并不一致，这一结论驳斥了“与白色形态型相关的性状需承担格外高昂的代价”这一观点。与之相反，黄褐色雌鸟的繁殖衰老出现时间早于白色雌鸟，且寿命更短，这或许反映了独自育雏所面临的多重生存挑战。本研究结果凸显了社群动态（social dynamics）在决定繁殖衰老模式中的核心作用。