Reversible plasticity in phenotypic traits allows organisms to cope with environmental variation within lifetimes, but costs of plasticity may limit just how well the phenotype matches the environmental optimum. An additional adaptive advantage of plasticity might be to reduce fitness variance, in other words: bet-hedging to maximize geometric (rather than simply arithmetic) mean fitness. Here, we model the evolution of plasticity in the form of reaction norm slopes, with increasing costs as the slope or degree of plasticity increases. We find that greater investment in plasticity (i.e. a steeper reaction norm slope) is favoured in scenarios promoting bet-hedging as a response to multiplicative fitness accumulation (i.e. coarser environmental grains and fewer time steps prior to reproduction), because plasticity lowers fitness variance across environmental conditions. In contrast, in scenarios with finer environmental grain and many time steps prior to reproduction, bet-hedging plays less of a role and individual-level optimization favours evolution of shallower reaction norm slopes. However, the opposite pattern holds if plasticity costs themselves result in increased fitness variation, as might be the case for production costs of plasticity that depend on how much change is made to the phenotype each time step. We discuss these contrasting predictions from this partitioning of adaptive plasticity into short-term individual benefits versus long-term genotypic (bet-hedging) benefits, and how this approach enhances our understanding of the evolution of optimum levels of plasticity in examples from thermal physiology to advances in avian lay dates.

中文翻译：

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个体可逆可塑性作为基因型级别的对冲策略。

表型性状的可逆可塑性允许生物体在一生中应对环境变化，但可塑性的成本可能会限制表型与环境最佳匹配的程度。可塑性的另一个适应性优势可能是减少适应度方差，换句话说：投注对冲以最大化几何（而不是简单的算术）平均适应度。在这里，我们以反应范数斜率的形式对塑性的演变进行建模，随着可塑性的斜率或程度的增加，成本也会增加。我们发现对可塑性的更大投资（即更陡峭的反应范数斜率）在促进对冲作为对乘法适应性积累的反应（即更粗的环境颗粒和繁殖前的更少时间步长）的场景中是有利的，因为可塑性降低了环境条件下的适应度差异。相比之下，在环境粒度更细且复制前有许多时间步长的场景中，对冲的作用较小，个人层面的优化有利于更浅的反应范数斜率的演化。然而，如果可塑性成本本身导致适应度变化增加，则相反的模式成立，就像可塑性的生产成本取决于每个时间步对表型进行多少变化的情况一样。我们通过将适应性可塑性划分为短期个人利益与长期基因型（对冲）利益来讨论这些对比预测，