Am Nat. 2024 Sep;204(3):E57-E69. doi: 10.1086/731295. Epub 2024 Jul 19.
AbstractMutualisms constitute a diverse class of ecologically important interactions, yet their ecological and evolutionary stability remain topics of debate in coevolutionary theory. Recent theoretical and empirical work has suggested that coevolutionary arms races may be involved in the maintenance of mutualistic interactions, sustaining mutually beneficial outcomes for interacting species while producing exaggerated traits. Here we present an individual-based model that evaluates how asynchronous life histories-that is, partners with different average lifespans-change the dynamics of trait coevolution, the expected fitness outcomes for species involved, and the dynamics of selection differentials across time for each species. Results indicate that a longer-lived mutualist will consistently "lose" an otherwise balanced coevolutionary arms race, being outpaced in both the mean trait value and fitness outcome compared with a shorter-lived partner. Furthermore, linear selection differentials on mutualistic traits become increasingly divergent as life histories become increasingly asynchronous, with the longer-lived species experiencing persistent directional selection and the shorter-lived species experiencing weaker, more inconsistent selection. These results suggest that asynchronous life histories can complicate the maintenance of mutualistic interactions via coevolutionary arms races and that detecting coevolution via selection differentials may be difficult when life histories are sufficiently divergent.
摘要 互利共生构成了一类具有重要生态意义的相互作用，但它们在协同进化理论中的生态和进化稳定性仍然是争论的话题。最近的理论和实证工作表明，协同进化军备竞赛可能参与了互利共生关系的维持，在产生夸张特征的同时，为相互作用的物种维持互利的结果。在这里，我们提出了一个基于个体的模型，该模型评估了不同的生活史（即具有不同平均寿命的伙伴）如何改变特征协同进化的动态、相关物种的预期适应度结果，以及每个物种随时间变化的选择差异的动态。结果表明，寿命较长的共生伙伴将始终“输掉”本来平衡的协同进化军备竞赛，与寿命较短的伙伴相比，其平均特征值和适应度结果都更快。此外，随着生活史变得越来越不同步，线性选择差异对共生特征的影响变得越来越大，寿命较长的物种经历持续的定向选择，而寿命较短的物种经历较弱、更不一致的选择。这些结果表明，当生活史足够不同步时，异步生活史可能会通过协同进化军备竞赛使互利共生关系的维持复杂化，并且通过选择差异来检测协同进化可能很困难。
