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，这一问题迄今仍存在争议。本研究以二态性白喉带鹀为研究对象，该物种是探索该问题的优质类群。该物种雌雄两性的不同形态均拥有独特的繁殖策略，且形态间的异型交配会形成具有差异化亲本抚育体系的配对类型。白色形态个体较棕褐色同类体色更艳丽、攻击性更强：白色形态雄鸟会通过竞争获取婚外交配机会，而棕褐色形态雄鸟则更专注于亲本抚育。棕褐色雄鸟与白色形态雌鸟会均等分担亲本抚育工作，而白色形态雄鸟几乎不会为棕褐色雌鸟提供抚育支持。本研究发现，雌雄两性均存在与形态相关的繁殖衰老模式：白色形态雄鸟的繁殖衰老程度较棕褐色雄鸟更为显著。该结果或反映出，随着衰老进程，维持高强度竞争性繁殖策略的难度不断提升，而非竞争性行为本身带来高生理代价——因为白色形态雄鸟的寿命本就更长。此外，跨性别而言，形态与繁殖衰老的关联并不一致，这一结果驳斥了与白色形态相关的性状具有极高代价的假说。相反，棕褐色形态雌鸟的繁殖衰老出现得更早，且寿命更短，这或许反映了无额外抚育支持的母性抚育所面临的挑战。本研究结果凸显了社会动态在决定繁殖衰老模式中的重要作用。