Data from: Decomposing variation in male reproductive success: age-specific variances and covariances through extra-pair and within-pair reproduction

1. Age-specific variances and covariances in reproductive success shape the total variance in lifetime reproductive success (LRS), age-specific opportunities for selection, and population demographic variance and effective size. Age-specific (co)variances in reproductive success achieved through different reproductive routes must therefore be quantified to predict population, phenotypic and evolutionary dynamics in age-structured populations. 2. While numerous studies have quantified age-specific variation in mean reproductive success, age-specific variances and covariances in reproductive success, and the contributions of different reproductive routes to these (co)variances, have not been comprehensively quantified in natural populations. 3. We applied ‘additive’ and ‘independent’ methods of variance decomposition to complete data describing apparent (social) and realised (genetic) age-specific reproductive success across 11 cohorts of socially monogamous but genetically polygynandrous song sparrows (Melospiza melodia). We thereby quantified age-specific (co)variances in male within-pair and extra-pair reproductive success (WPRS and EPRS) and the contributions of these (co)variances to the total variances in age-specific reproductive success and LRS. 4. ‘Additive’ decomposition showed that within-age and among-age (co)variances in WPRS across males aged 2–4 years contributed most to the total variance in LRS. Age-specific (co)variances in EPRS contributed relatively little. However, extra-pair reproduction altered age-specific variances in reproductive success relative to the social mating system, and hence altered the relative contributions of age-specific reproductive success to the total variance in LRS. 5. ‘Independent’ decomposition showed that the (co)variances in age-specific WPRS, EPRS and total reproductive success, and the resulting opportunities for selection, varied substantially across males that survived to each age. Furthermore, extra-pair reproduction increased the variance in age-specific reproductive success relative to the social mating system to a degree that increased across successive age classes. 6. This comprehensive decomposition of the total variances in age-specific reproductive success and LRS into age-specific (co)variances attributable to two reproductive routes showed that within-age and among-age covariances contributed substantially to the total variance and that extra-pair reproduction can alter the (co)variance structure of age-specific reproductive success. Such covariances and impacts should consequently be integrated into theoretical assessments of demographic and evolutionary processes in age-structured populations.

1. 繁殖成功率的年龄特异性方差与协方差，会塑造终生繁殖成功率（lifetime reproductive success, LRS）的总方差、年龄特异性选择机会，以及种群人口学方差与有效种群大小。因此，若要预测年龄结构化种群的种群动态、表型动态与进化动态，必须量化通过不同繁殖路径实现的繁殖成功率的年龄特异性（协）方差。
2. 尽管已有大量研究量化了繁殖成功率均值的年龄特异性变异，但在自然种群中，繁殖成功率的年龄特异性方差与协方差，以及不同繁殖路径对这类（协）方差的贡献，尚未得到全面量化。
3. 本研究针对11个世代的社会单配制但遗传上多配混交的歌带鹀（Melospiza melodia）数据集，采用“加性”与“独立”两种方差分解方法，分析了表观（社会）与实际（遗传）的年龄特异性繁殖成功率数据。据此量化了雄性配偶内繁殖成功率（within-pair reproductive success, WPRS）与配偶外繁殖成功率（extra-pair reproductive success, EPRS）的年龄特异性（协）方差，以及这类（协）方差对年龄特异性繁殖成功率与LRS总方差的贡献。
4. “加性”分解结果显示，2至4岁雄性的配偶内繁殖成功率的年龄内与年龄间（协）方差，对LRS总方差的贡献最大；而配偶外繁殖成功率的年龄特异性（协）方差贡献相对较小。不过，相较于社会交配系统，配偶外繁殖会改变繁殖成功率的年龄特异性方差，进而改变年龄特异性繁殖成功率对LRS总方差的相对贡献。
5. “独立”分解结果表明，不同存活至各年龄的雄性，其年龄特异性配偶内繁殖成功率、配偶外繁殖成功率与总繁殖成功率的（协）方差，以及由此产生的选择机会，均存在显著差异。此外，相较于社会交配系统，配偶外繁殖会提升繁殖成功率的年龄特异性方差，且这种提升程度随年龄层级递增而加大。
6. 本研究将年龄特异性繁殖成功率与LRS的总方差，分解为归因于两种繁殖路径的年龄特异性（协）方差，该全面分解结果显示：年龄内与年龄间协方差对总方差的贡献显著，且配偶外繁殖可改变繁殖成功率的年龄特异性（协）方差结构。因此，这类协方差及其影响，应当被纳入年龄结构化种群的人口学与进化过程的理论评估中。