Fluctuating environmental conditions have consequences for the evolution of life histories because they cause fitness variance. This variance can favor risk-spreading strategies, often known as bet-hedging strategies, in which growth or reproduction is spread over time or space, with some costs, but greater certainty of success. An important example is seed dormancy in annual plants, in which some fraction of seed remains dormant at any given germination opportunity with the potential of germinating later when environmental conditions may differ. Previous theory shows that environmental variation is critical for the evolution of dormancy. However, these studies have focused on temporal variation in reproduction, ignoring the strong observed effects of environmental variation on the germination fraction, a major contributor to fitness variance. We ask what effects germination fluctuations have on selection for dormancy by adding germination fluctuations to existing density-independent (d.i.) and density-dependent (d.d.) models of annual plant dynamics, extending previous analyses by including temporally fluctuating germination. Specifically, we ask how germination variance affects selection on the temporal average germination fraction, here used to define dormancy. When present alone, or when independently varying with other fitness components, germination fluctuations do not affect selection for dormancy in the d.i. model, despite generating fitness variance because this variance contribution is not reduced by higher dormancy. Germination fluctuations have strong effects in the d.d. model, favoring dormancy when present either alone or coupled with variation affecting plant growth. This is because germination variation causes seedling density to vary, which causes variable reproduction through variable intraspecific competition. Dormancy is advantaged under variable reproduction because it creates a more convex relationship between population growth and reproduction leading to benefits from nonlinear averaging. Predictive germination, a positive statistical association between germination and growth, weakens selection for dormancy under strong competition and strengthens it when competition is weak. Our results suggest that variable germination is a potential explanation for high levels of dormancy observed in nature, with implications for life-history theory for fluctuating environments.

中文翻译：

---

当与幼苗竞争结合时，发芽变异有利于种子休眠的进化。

不断变化的环境条件会影响生活史的发展，因为它们会导致适应性差异。这种差异可能有利于风险分散策略，通常被称为对冲策略，在这种策略中，增长或再生产是随时间或空间分布的，但付出了一定的代价，但成功的可能性更大。一个重要的例子是一年生植物的种子休眠，其中某些种子在任何给定的发芽机会中都保持休眠状态，并且当环境条件可能不同时，有可能在以后发芽。先前的理论表明，环境变化对于休眠的发展至关重要。但是，这些研究集中在繁殖的时间变化上，而忽略了环境变化对发芽率的强烈影响，而发芽率是适应性变化的主要因素。我们通过将发芽波动添加到现有的年度植物动力学的独立于密度的（di）和依赖密度（dd）的模型中来扩展发芽波动对休眠选择的影响，并通过包括随时间波动的发芽来扩展先前的分析。具体来说，我们询问发芽方差如何影响对时间平均发芽分数的选择，在此将其用于定义休眠。当单独出现或与其他适应性组件独立变化时，发芽波动不会影响di模型中休眠的选择，尽管会产生适应性方差，因为较高的休眠不会降低方差的贡献。萌发起伏在dd模型中有很强的影响，当单独存在或与影响植物生长的变异同时存在时，有利于休眠。这是因为发芽变化会导致幼苗密度发生变化，从而通过可变的种内竞争导致可变的繁殖。休眠在变量再生产下具有优势，因为它在种群增长与再生产之间建立了更凸的关系，从而从非线性平均中受益。预测性发芽是发芽与生长之间的正向统计关联，它会削弱在激烈竞争下对休眠的选择，而在竞争较弱的情况下会增强休眠。我们的结果表明，可变发芽是自然界中观察到的高休眠水平的潜在解释，这对波动环境下的生命历史理论具有重要意义。通过种内竞争而引起的繁殖繁殖。休眠在变量再生产下具有优势，因为它在种群增长与再生产之间建立了更凸的关系，从而从非线性平均中受益。预测性发芽是发芽与生长之间的正向统计关联，它会削弱在激烈竞争下对休眠的选择，而在竞争较弱的情况下会增强休眠。我们的结果表明，可变发芽是自然界中观察到的高休眠水平的潜在解释，这对波动环境下的生命历史理论具有重要意义。通过种内竞争而引起的繁殖繁殖。休眠在变量再生产下具有优势，因为它在种群增长与再生产之间建立了更凸的关系，从而从非线性平均中受益。预测性发芽是发芽与生长之间的正向统计关联，它会削弱在激烈竞争下对休眠的选择，而在竞争较弱的情况下会增强休眠的选择。我们的结果表明，可变发芽是自然界中观察到的高休眠水平的潜在解释，这对波动环境下的生命历史理论具有重要意义。预测性发芽是发芽与生长之间的正向统计关联，它会削弱在激烈竞争下对休眠的选择，而在竞争较弱的情况下会增强休眠。我们的结果表明，可变发芽是自然界中观察到的高休眠水平的潜在解释，这对波动环境下的生命历史理论具有重要意义。预测性发芽是发芽与生长之间的正向统计关联，它会削弱在激烈竞争下对休眠的选择，而在竞争较弱的情况下会增强休眠。我们的结果表明，可变发芽是自然界中观察到的高休眠水平的潜在解释，这对波动环境下的生命历史理论具有重要意义。