Data from: Playing smart vs. playing safe: the joint expression of phenotypic plasticity and potential bet hedging across and within thermal environments

Adaptive phenotypic plasticity evolves when cues reliably predict fitness consequences of life-history decisions, whereas bet hedging evolves when environments are unpredictable. These modes of response should be jointly expressed, because environmental variance is composed of both predictable and unpredictable components. However, little attention has been paid to the joint expression of plasticity and bet hedging. Here, I examine the simultaneous expression of plasticity in germination rate and two potential bet-hedging traits – germination fraction and within-season diversification in timing of germination – in seeds from multiple seed families of five geographically distant populations of Lobelia inflata (L.) subjected to a thermal gradient. Populations differ in germination plasticity to temperature, in total germination fraction and in the expression of potential diversification in the timing of germination. The observation of a negative partial correlation between the expression of plasticity and germination variance (potential diversification), and a positive correlation between plasticity and germination fraction is suggestive of a trade-off between modes of response to environmental variance. If the observed correlations are indicative of those between adaptive plasticity and bet hedging, we expect an optimal balance to exist and differ among populations. I discuss the challenges involved in testing whether the balance between plasticity and bet hedging depends on the relative predictability of environmental variance.

当环境线索能够可靠预示生活史决策的适合度后果时，适应性表型可塑性（adaptive phenotypic plasticity）会得以演化；而当环境不可预测时，风险对冲（bet hedging）策略则会演化形成。由于环境变异同时包含可预测与不可预测组分，这两种响应模式本应被共同表达，但目前学界对可塑性与风险对冲的协同表达关注甚少。本研究以五个地理分布相距甚远的美洲山梗菜（Lobelia inflata (L.)）种群的多个种子家系为实验材料，设置温度梯度处理，探究其萌发速率的可塑性，以及两种潜在风险对冲性状——萌发率与萌发时间的季内分化——的同步表达情况。不同种群在温度响应的萌发可塑性、总萌发率以及萌发时间潜在分化的表达模式上均存在差异。本研究观测到，可塑性表达与萌发变异（即潜在分化）之间呈负偏相关，而可塑性与总萌发率之间呈正相关，这暗示环境变异的不同响应模式间存在权衡关系。若上述观测到的相关关系能够反映适应性表型可塑性与风险对冲间的真实关联，则可推测二者间存在最优平衡，且该平衡在不同种群间存在差异。本研究最后讨论了检验“可塑性与风险对冲间的平衡取决于环境变异的相对可预测性”这一假说所面临的实验挑战。