Predictive adaptive responses (PARs) are a form of developmental plasticity in which the developmental response to an environmental cue experienced early in life is delayed and yet, at the same time, the induced phenotype anticipates (i.e., is completely developed before) exposure to the eventual environmental state predicted by the cue, in which the phenotype is adaptive. We model this sequence of events to discover, under various assumptions concerning the cost of development, what lengths of delay, developmental time, and anticipation are optimal. We find that in many scenarios modeled, development of the induced phenotype should be completed at the exact same time that the environmental exposure relevant to the induced phenotype begins: that is, in contrast to our observed cases of PARs, there should be no anticipation. Moreover, unless slow development is costly, development should commence immediately after the cue: there should be no delay. Thus, PARs, which normally have non-zero delays and/or anticipation, are highly unusual. Importantly, the exceptions to these predictions of zero delays and anticipation occurred when developmental time was fixed and delaying development was increasingly costly. We suggest, therefore, that PARs will only evolve under three kinds of circumstances: (i) there are strong timing constraints on the cue and the environmental status, (ii) delaying development is costly, and development time is either fixed or slow development is costly, or (iii) when the period between the cue and the eventual environmental change is variable and the cost of not completing development before the change is high. These predictions are empirically testable.

中文翻译：

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预测自适应响应的最佳时机模型

预测性适应性反应 (PAR) 是一种发育可塑性形式，其中对生命早期经历的环境线索的发育反应被延迟，但同时，诱导的表型预期（即，之前完全发育）暴露于由线索预测的最终环境状态，其中表型是适应性的。我们对这一系列事件进行建模，以发现在有关开发成本的各种假设下，延迟的长度、开发时间和预期是最佳的。我们发现，在许多模拟的场景中，诱导表型的发展应该在与诱导表型相关的环境暴露开始的同时完成：也就是说，与我们观察到的 PAR 病例相比，应该没有预期。而且，除非缓慢开发成本高昂，否则开发应在提示后立即开始：不应拖延。因此，通常具有非零延迟和/或预期的 PAR 是非常不寻常的。重要的是，当开发时间固定并且延迟开发成本越来越高时，这些零延迟和预期预测的例外情况发生。因此，我们建议 PAR 只会在三种情况下进化：（i）对提示和环境状态有很强的时间限制，（ii）延迟开发成本高昂，开发时间固定或开发缓慢代价高昂，或 (iii) 提示和最终环境变化之间的时间是可变的，并且在变化之前未完成开发的成本很高。这些预测是可以通过经验检验的。