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.

诸多动物类群中，繁殖成功率与年龄存在显著关联：生命早期随年龄增长而提升，随后进入生殖衰老（reproductive senescence）阶段。在社会一夫一妻制（socially monogamous）但遗传上为多配偶制（genetically polygamous）的物种中，这一规律催生了一个有趣的研究可能：雄性的婚内父权（within-pair paternity）与婚外父权（extra-pair paternity）成功率随年龄变化的动态轨迹可能存在差异。本研究基于某岛屿种群家麻雀（Passer domesticus）长达13年的监测数据，采用个体内分析（within-individual analyses）方法，同时探究了上述两类父权成功率与年龄的关联。正如预期，研究发现婚内父权与婚外父权成功率均随年龄增长而提升，随后出现类似生殖衰老的下降趋势。但二者的年龄动态轨迹存在显著差异：婚外父权成功率在生命早期的提升速度更快（尽管该差异未达统计学显著性），且与婚内父权成功率相比，其衰老性下降的时间平均延迟了1.5年。这种轨迹差异表明，两种可选交配策略（mating tactics）的收益应随年龄变化而有所不同。雄性个体或许会根据自身当前年龄，将繁殖投入在婚内交配与婚外交配之间进行分配，以最大化两种策略带来的综合收益。这些交配策略与年龄特异性死亡率（age-specific mortality）之间的相互作用，或可解释物种内部及物种间观察到的婚外父权发生率差异。