Department of Mathematical Sciences, University of Bath, Bath, UK.
Milner Centre for Evolution, University of Bath, Bath, UK.
Bull Math Biol. 2023 Apr 15;85(5):42. doi: 10.1007/s11538-023-01144-5.
Many organisms experience an increase in disease resistance as they age, but the time of life at which this change occurs varies. Increases in resistance are partially due to prior exposure and physiological constraints, but these cannot fully explain the observed patterns of age-related resistance. An alternative explanation is that developing resistance at an earlier age incurs costs to other life-history traits. Here, we explore how trade-offs with host reproduction or mortality affect the evolution of the onset of resistance, depending on when during the host's life cycle the costs are paid (only when resistance is developing, only when resistant or throughout the lifetime). We find that the timing of the costs is crucial to determining evolutionary outcomes, often making the difference between resistance developing at an early or late age. Accurate modelling of biological systems therefore relies on knowing not only the shape of trade-offs but also when they take effect. We also find that the evolution of the rate of onset of resistance can result in evolutionary branching. This provides an alternative, possible evolutionary history of populations which are dimorphic in disease resistance, where the rate of onset of resistance has diversified rather than the level of resistance.
许多生物随着年龄的增长，其疾病抵抗力会增强，但这种变化发生的时间因生物种类而异。抵抗力的增强部分归因于先前的暴露和生理限制，但这些并不能完全解释与年龄相关的抵抗力的观察模式。另一种解释是，在较早的年龄发展出抵抗力会对其他生活史特征产生代价。在这里，我们探讨了宿主繁殖或死亡率的权衡如何影响抵抗力开始出现的进化，具体取决于代价是在宿主生命周期的何时（仅在发展抵抗力时、仅在有抵抗力时或整个生命周期中）支付。我们发现，代价的时间对于确定进化结果至关重要，这往往决定了抵抗力是在早期还是晚期发展。因此，准确模拟生物系统不仅需要知道权衡的形状，还需要知道它们何时起作用。我们还发现，抵抗力开始出现的速度的进化可能导致进化分支。这为在疾病抵抗力上存在二态性的种群提供了另一种可能的进化历史，其中抵抗力开始出现的速度已经多样化，而不是抵抗力的水平。
