Department of Biology, University of Oxford, 11a Mansfield Road, Oxford, OX1 3SZ, UK.
Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands.
Commun Biol. 2023 Sep 5;6(1):909. doi: 10.1038/s42003-023-05260-9.
Hamilton's force of selection acting against age-specific mortality is constant and maximal prior to the age of first reproduction, before declining to zero at the age of last reproduction. The force of selection acting on age-specific reproduction declines monotonically from birth in a growing or stationary population. Central to these results is the assumption that individuals do not interact with one another. This assumption is violated in social organisms, where an individual's survival and/or reproduction may shape the inclusive fitness of other group members. Yet, it remains unclear how the forces of selection might be modified when inclusive fitness, rather than population growth rate, is considered the appropriate metric for fitness. Here, we derive such inclusive fitness forces of selection, and show that selection on age-specific survival is not always constant before maturity, and can remain above zero in post-reproductive age classes. We also show how the force of selection on age-specific reproduction does not always decline monotonically from birth, but instead depends on the balance of costs and benefits of increasing reproduction to both direct and indirect fitness. Our theoretical framework provides an opportunity to expand our understanding of senescence across social species.
汉密尔顿选择压力作用于特定年龄的死亡率，在首次繁殖年龄之前是恒定且最大的，之后下降到最后一次繁殖年龄的零。选择压力作用于特定年龄的繁殖率从增长或稳定种群的出生开始单调下降。这些结果的核心是假设个体之间不会相互作用。这个假设在社会生物中被违反了，因为个体的生存和/或繁殖可能会影响其他群体成员的适合度。然而，当将适合度定义为包括群体成员的适合度，而不是种群增长率时，选择压力如何被修改仍然不清楚。在这里，我们推导出了这种包容性适合度选择压力，并表明在成熟之前，特定年龄的生存选择并不总是恒定的，并且在生殖后年龄组中仍然可以保持正值。我们还展示了特定年龄的繁殖选择压力并不总是从出生开始单调下降，而是取决于增加繁殖对直接和间接适合度的成本和收益的平衡。我们的理论框架为扩大对社会性物种衰老的理解提供了机会。
