Data from: Mechanisms of thermal adaptation and evolutionary potential of conspecific populations to changing environments

Heterogeneous and ever-changing thermal environments drive the evolution of populations and species, especially when extreme conditions increase selection pressure for traits influencing fitness. However, projections of biological diversity under scenarios of climate change rarely consider evolutionary adaptive potential of natural species. In this study, we tested for mechanistic evidence of evolutionary thermal adaptation among ecologically divergent redband trout populations (Oncorhynchus mykiss gairdneri) in cardiorespiratory function, cellular response and genomic variation. In a common garden environment, fish from an extreme desert climate had significantly higher critical thermal maximum (p<0.05) and broader optimum thermal window for aerobic scope (>3°C) than fish from cooler montane climate. In addition, the desert population had the highest maximum heart rate during warming (20% greater than montane populations), indicating improved capacity to deliver oxygen to internal tissues. In response to acute heat stress, distinct sets of cardiac genes were induced among ecotypes, which helps to explain the differences in cardiorespiratory function. Candidate genomic markers and genes underlying these physiological adaptations were also pinpointed, such as genes involved in stress response and metabolic activity (hsp40, ldh-b and camkk2). These markers were developed into a multi-variate model that not only accurately predicted critical thermal maxima, but also evolutionary limit of thermal adaptation in these specific redband trout populations relative to the expected limit for the species. This study demonstrates mechanisms and limitations of an aquatic species to evolve under changing environments that can be incorporated into advanced models to predict ecological consequences of climate change for natural organisms.异质性且持续动态变化的热环境驱动种群与物种的演化，当极端环境条件提升了影响个体适合度的性状的选择压力时，这一演化驱动效应尤为显著。然而，现有气候变化情景下的生物多样性预测研究，极少考虑自然物种的演化适应潜力。本研究针对生态分化的红带鳟（Oncorhynchus mykiss gairdneri）种群，从心肺功能、细胞应激应答及基因组变异三个维度，探寻演化热适应的机制性证据。在共同花园实验环境中，源自极端荒漠气候的红带鳟种群，其临界热最大值（critical thermal maximum）显著高于山地种群（p<0.05），且有氧代谢范围（aerobic scope）的最优热窗口较山地种群宽逾3℃。此外，荒漠种群在升温过程中的最大心率最高，较山地种群高出20%，这表明其向体内组织输送氧气的能力得到了优化提升。在急性热应激条件下，不同生态型的红带鳟会诱导出特异性的心脏基因表达谱，这一现象可有效解释不同种群间心肺功能的差异。本研究还确定了支撑这些生理适应特征的候选基因组标记与功能基因，例如参与应激应答与代谢活动的基因（hsp40、ldh-b与camkk2）。研究人员将上述标记开发为多元预测模型，该模型不仅可精准预测临界热最大值，还能相较于该物种的预期适应极限，精准预测这些特定红带鳟种群的热适应演化上限。本研究阐明了水生物种在动态变化环境下的演化机制与演化局限，该成果可被整合进进阶预测模型，用以预判气候变化对自然生物群落的生态影响。