Data from: The evolution of optimal emergence times: bet hedging and the quest for an ideal free temporal distribution of individuals

Proper timing of activities is one of the principal challenges faced by most organisms. Organisms need to account for various aspects in decision making like avoiding inordinate risks, synchronizing with resource availability, or finding mates. We provide analytical and simulation models to investigate the influence of life expectancy, resource competition and unpredictable environmental conditions (environmental uncertainty) on the evolutionarily stable distribution of emergence times in organisms depending on seasonally available resources. We focus on the partitioning of total phenotypic variance in emergence times into 1) genetic variance in mean emergence times between lineages and 2) environmental trait variance that determines the intra-lineage variance in the timing of emergence. Both, life expectancy of organisms and intensity of competition severely influence the evolutionary response to environmental uncertainty. Our main findings can be summarized as follows: 1) in general diversifying bet hedging (environmental trait variance) is the adequate mechanism to reduce the risk arising from environmental uncertainty while conservative bet hedging, i.e. delaying emergence into 'safe' phases of the season is restricted to short lived organisms and to situations with vanishing competition. 2) Environmental trait variance increases with increasing environmental uncertainty whereas 3) significant genetic variance evolves only under severe resource competition; it is driven by selection for an ideal free distribution of emergence times. 4) The level of genetic variance evolving declines with increasing life expectancy of organisms. 5) With sufficiently short life expectancy evolutionary branching and coexistence of distinctly different emergence strategies occurs; the number of co-occurring strategies is determined by the level of environmental uncertainty. Our model provides cues for understanding how different ecological factors contribute and interact to shape the evolution of emergence strategies.

活动的适时调控是多数生物体面临的核心挑战之一。生物体在决策过程中需兼顾多重维度，例如规避过高风险、匹配资源可获得周期，或是寻觅配偶。我们构建了分析模型与仿真模型，用以探究寿命、资源竞争以及不可预测的环境条件（环境不确定性（environmental uncertainty））对依赖季节性可利用资源的生物体出现时间的进化稳定分布的影响。我们重点关注将出现时间的总表型方差划分为两部分：1）不同谱系间平均出现时间的遗传方差；2）决定谱系内出现时间差异的环境性状方差。生物体的寿命与竞争强度均会显著影响其对环境不确定性的进化响应。我们的主要研究结论可归纳如下：1）总体而言，多样化避险策略（diversifying bet hedging）是降低环境不确定性所带来风险的有效机制；而保守避险策略，即通过将出现时间推迟至季节内的‘安全’时段，则仅适用于短命生物体以及竞争近乎消失的场景。2）环境性状方差会随环境不确定性的提升而增大；3）显著的遗传方差仅会在激烈的资源竞争条件下进化而来，其演化驱动力源于对出现时间理想自由分布的选择。4）进化形成的遗传方差水平会随生物体寿命的延长而降低。5）当寿命足够短时，会发生进化分支并共存多种截然不同的出现策略；共存策略的数量由环境不确定性的程度决定。本模型为解析不同生态因子如何共同作用、相互影响，进而塑造出现策略的演化过程提供了理论参考。