Data from: Age-dependent trajectories differ between within-pair and extra-pair paternity success

Reproductive success is associated with age in many taxa, increasing in early life followed by reproductive senescence. In socially monogamous, but genetically polygamous species, this generates the interesting possibility of differential trajectories of within-pair and extra-pair siring success with age in males. We investigate these relationships simultaneously using within-individual analyses with 13 years of data from an insular house sparrow (Passer domesticus) population. As expected, we found that both within- and extra-pair paternity success increased with age, followed by a senescence-like decline. However, the age trajectories of within- and extra-pair paternity successes differed significantly, with the extra-pair paternity success increasing faster, albeit non-significantly so, in early life, and showing a delayed decline by 1.5 years on average later in life compared to within-pair paternity success. These different trajectories indicate that the two alternative mating tactics should have age-dependent payoffs. Males may partition their reproductive effort between within- and extra-pair matings depending on their current age in order to reap the maximal combined benefit from both strategies. The interplay between these mating strategies and age-specific mortality may explain the variation in rates of extra-pair paternity observed within and between-species.

诸多分类群（taxa）的繁殖成功率与年龄密切相关，通常在生命早期随年龄增长而提升，随后出现生殖衰老（reproductive senescence）。在社会一夫一妻制但遗传上属于多配制的物种中，这一规律催生了一个有趣的科学假设：雄性个体的配偶内与配偶外父权成功率，可能随年龄呈现差异化的变化轨迹。我们依托某岛屿家麻雀（Passer domesticus）种群长达13年的监测数据，采用个体内分析方法同时探究了上述关联模式。正如预期，研究发现配偶内与配偶外父权成功率均随年龄先升后降，呈现类似衰老的衰退趋势。然而二者的年龄轨迹存在显著差异：配偶外父权成功率在生命早期的上升速率更快（尽管该差异未达统计显著性水平），且相较于配偶内父权成功率，其衰退时间平均延迟了1.5年。上述差异化的年龄轨迹表明，两种备选交配策略的收益应随年龄发生变化。雄性个体或可根据自身当前年龄，调整在配偶内与配偶外交配间分配的繁殖投入，从而从两种策略中获取最大化的综合收益。交配策略与年龄特异性死亡率之间的相互作用，或可解释不同物种内部以及物种间观察到的配偶外父权发生率差异。