Data from: Environmental stress increases the magnitude of non-additive genetic variation in offspring fitness in the frog Crinia georgiana

When organisms encounter heterogeneous environments, selection may favor the ability of individuals to tailor their phenotypes to suit the prevailing conditions. Understanding the genetic basis of plastic responses is therefore vital for predicting whether susceptible populations can adapt and persist under new selection pressures. Here, we investigated whether there is potential for adaptive plasticity in development time in the quacking frog Crinia georgiana, a species experiencing a drying climate. Using a North Carolina II breeding design, we exposed 90 family groups to two water depth treatments (baseline and low-water) late in larval development. We estimated the contribution of additive and non-additive sources of genetic variation to early offspring fitness under both environments. Our results revealed a marked decline in larval fitness under the stressful (low-water) rearing environment, but also that additive genetic variation was negligible for all traits. However, in most cases we found significant sire-by-dam interactions, indicating the importance of non-additive genetic variation for offspring fitness. Moreover, sire-by-dam interactions were modified by the treatment, indicating that patterns of non-additive genetic variance depend on environmental context. For all traits, we found higher levels of non-additive genetic variation (relative to total phenotypic variation) when larvae were reared under stressful conditions, suggesting that the fitness costs associated with incompatible parental crosses (e.g. homozygous deleterious recessive alleles) will only be expressed when water availability is low. Taken together, our results highlight the need to consider patterns of non-additive genetic variation under contrasting selective regimes when considering the resilience of species to environmental change.

当生物体遭遇异质环境时，自然选择可能会青睐那些能够调整自身表型以适应当前环境条件的个体。因此，阐明表型可塑性响应的遗传基础，对于预测易受影响的种群能否在新的选择压力下适应并存续至关重要。本研究以正经历气候干旱化的鸣蛙（Crinia georgiana）为研究对象，探讨其发育时长是否存在适应性表型可塑性（adaptive plasticity）潜力。我们采用北卡罗来纳II式育种设计（North Carolina II breeding design），在幼虫发育后期将90个家系群分别置于两种水深处理（基线组与低水深组）的环境中饲养。我们评估了两种环境下，加性遗传变异（additive genetic variation）与非加性遗传变异（non-additive genetic variation）来源对早期后代适合度的贡献。研究结果显示，在胁迫性（低水深）饲养环境中，幼虫适合度出现显著下降；同时，所有性状的加性遗传变异均微乎其微。不过在多数性状中，我们均检测到了显著的父本-母本互作效应，这表明非加性遗传变异对后代适合度具有重要意义。此外，该互作效应会随饲养处理环境的不同而发生改变，说明非加性遗传方差的模式依赖于环境背景。对于所有性状而言，当幼虫在胁迫环境下饲养时，我们观测到的非加性遗传变异水平（相对于总表型变异）更高，这意味着与不相容亲本杂交相关的适合度代价（例如纯合有害隐性等位基因），仅会在水资源匮乏的条件下得以表现。综上，本研究结果强调，在评估物种应对环境变化的恢复力时，需考虑不同选择情境下的非加性遗传变异模式。