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...繁殖策略如何塑造自然种群的衰老模式，迄今仍存在广泛争议。我们以存在形态二形性的白喉带鹀（white-throated sparrow）为研究对象，探究繁殖衰老（reproductive senescence）问题，该物种是开展此类研究的理想模型。该物种雌雄两性的不同形态个体均采用截然不同的繁殖策略，且形态型间的异型配对（disassortative pairing）会形成具有独特育幼体系的配偶类型。白色形态个体的羽色更鲜亮、攻击性强于棕褐色形态个体；白色形态的雄性会通过竞争获取配偶外交配（extra-pair matings）机会，而棕褐色雄性则更专注于育幼工作。棕褐色雄性与白色雌性会均等分担育幼责任，而白色雄性几乎不会为棕褐色雌性提供育幼支持。我们在雌雄两性中均发现了形态特异性的繁殖衰老模式：白色形态雄性的繁殖衰老程度显著高于棕褐色雄性。该结果大概率反映了随着衰老进程推进，维持高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的高昂生理代价……