Stickleback (Gasterosteus aculeatas) egg size and offspring size in four climate scenarios

Increasing climate variability may pose an even greater risk to species than climate warming because temperature fluctuations can amplify adverse impacts of directional warming on fitness-related traits. Here, the influence of directional warming and increasing climate variability on marine stickleback fish (Gasterosteus aculeatus) offspring size variation was investigated by simulating changes to the mean and variance of ocean temperatures predicted under climate change. Reproductive traits of mothers and offspring size reaction norms across four climate scenarios were examined to assess the roles of standing genetic variation, transgenerational and within-generation plasticity in adaptive potential. Mothers acclimated to directional warming produced smaller eggs than mothers in constant, ambient temperatures, whereas mothers in a predictably variable environment (weekly change between temperatures) produced a range of egg sizes, possibly reflecting a diversified bet hedging strategy. Offspring size post-hatch was mostly influenced by genotype by environment interactions and not transgenerational effects. Offspring size reaction norms also differed depending on the type of environmental predictability (predictably variable vs. stochastic), with offspring reaching the largest sizes in the stochastic environment. Release of cryptic genetic variation for offspring size in the stochastic environment suggests hidden evolutionary potential in this wild population to respond to changes in environmental predictability.

日益加剧的气候变异性或许比气候变暖对物种构成更大威胁，因为温度波动会放大定向变暖对适合度相关性状的不利影响。本研究通过模拟气候变化下预测的海洋温度均值与方差变化，探究了定向变暖与加剧的气候变异性对海洋三刺鱼（Gasterosteus aculeatus）后代体型变异的影响。本研究对四种气候情景下的母体繁殖性状与后代体型反应规范（reaction norm）进行了分析，以评估现存遗传变异（standing genetic variation）、跨代可塑性（transgenerational plasticity）及代内可塑性在适应潜力中的作用。经定向变暖驯化的母体所产鱼卵，体型小于处于恒定环境温度下的母体；而处于可预测波动环境（每周温度变化）中的母体则产出大小不一的鱼卵，这或许反映了一种多样化风险对冲（bet hedging）策略。孵化后的后代体型主要受基因型-环境互作（genotype by environment interaction）影响，而非跨代效应。后代体型反应规范也因环境可预测性类型（可预测波动 vs. 随机（stochastic））而异，后代在随机环境中体型最大。随机环境下后代体型相关隐性遗传变异（cryptic genetic variation）的释放，表明该野生种群存在应对环境可预测性变化的潜在进化潜力。