Department of Life Sciences, Imperial College London, Silwood Park, Ascot, Berkshire, United Kingdom.
Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands.
PLoS One. 2022 Apr 22;17(4):e0260905. doi: 10.1371/journal.pone.0260905. eCollection 2022.
Fitness is at the core of evolutionary theory, but it is difficult to measure accurately. One way to measure long-term fitness is by calculating the individual's reproductive value, which represents the expected number of allele copies an individual passes on to distant future generations. However, this metric of fitness is scarcely used because the estimation of individual's reproductive value requires long-term pedigree data, which is rarely available in wild populations where following individuals from birth to death is often impossible. Wild study systems therefore use short-term fitness metrics as proxies, such as the number of offspring produced. This study compared two frequently used short-term metrics for fitness obtained at different offspring life stages (eggs, hatchlings, fledglings and recruits), and compared their ability to predict reproductive values derived from the genetic pedigree of a wild passerine bird population. We used twenty years of precise field observations and a near-complete genetic pedigree to calculate reproductive success, individual growth rate and de-lifed fitness as lifetime fitness measures, and as annual de-lifed fitness. We compared the power of these metrics to predict reproductive values and lineage survival to the end of the study period. The three short-term fitness proxies predict the reproductive values and lineage survival only when measured at the recruit stage. There were no significant differences between the different fitness proxies at the same offspring stages in predicting the reproductive values and lineage survival. Annual fitness at one year old predicted reproductive values equally well as lifetime de-lifed fitness. However, none of the short-term fitness proxies were strongly associated with the reproductive values. The commonly used short-term fitness proxies best predict long-term fitness when measured at recruitment stage. Thus, because lifetime fitness measured at recruit stage and annual fitness in the first year of life were the best proxies of long-term fitness in short-lived birds, we encourage their future use.
健康是进化理论的核心，但很难准确衡量。衡量长期健康的一种方法是计算个体的生殖价值，它代表个体传递给遥远后代的等位基因拷贝数。然而，这种健康衡量标准很少被使用，因为估计个体的生殖价值需要长期的系谱数据，而在野外种群中，很少有这种数据，因为从出生到死亡跟踪个体通常是不可能的。因此，野外研究系统使用短期健康衡量标准作为替代指标，例如产生的后代数量。本研究比较了两种常用于不同后代生命阶段（卵、雏鸟、幼鸟和新兵）的短期健康衡量标准，并比较了它们预测从野生雀形目鸟类种群遗传系谱中得出的生殖价值的能力。我们使用了二十年的精确实地观测和几乎完整的遗传系谱来计算生殖成功率、个体增长率和终身生存力作为寿命健康衡量标准，并作为年度生存力衡量标准。我们比较了这些指标预测生殖价值和谱系生存到研究结束的能力。当在新兵阶段测量时，三种短期健康替代指标仅可预测生殖价值和谱系生存。在预测生殖价值和谱系生存方面，同一后代阶段的不同健康替代指标之间没有显著差异。一岁时的年度健康状况与终身生存力同样能很好地预测生殖价值。然而，没有一种短期健康替代指标与生殖价值有很强的关联。当在招募阶段测量时，常用的短期健康替代指标最能预测长期健康。因此，由于在新兵阶段测量的终身生存力和第一年的年度生存力是短寿命鸟类长期生存力的最佳替代指标，我们鼓励未来使用它们。
