Data from: Indirect genetic effects underlie oxygen-limited thermal tolerance within a coastal population of chinook salmon

With global temperatures projected to surpass the limits of thermal tolerance for many species, evaluating the heritable variation underlying thermal tolerance is critical for understanding the potential for adaptation to climate change. We examined the evolutionary potential of thermal tolerance within a population of chinook salmon (Oncorhynchus tshawytscha) by conducting a full-factorial breeding design and measuring the thermal performance of cardiac function and the critical thermal maximum (CTmax) of offspring from each family. Additive genetic variation in offspring phenotype was mostly negligible, although these direct genetic effects explained 53% of the variation in resting heart rate (fH). Conversely, maternal effects had a significant influence on resting fH, scope for fH, cardiac arrhythmia temperature and CTmax. These maternal effects were associated with egg size, as indicated by strong relationships between the mean egg diameter of mothers and offspring thermal tolerance. Because egg size can be highly heritable in chinook salmon, our finding indicates that the maternal effects of egg size constitute an indirect genetic effect contributing to thermal tolerance. Such indirect genetic effects could accelerate evolutionary responses to the selection imposed by rising temperatures and could contribute to the population-specific thermal tolerance that has recently been uncovered among Pacific salmon populations.随着全球气温预计将突破众多物种的热耐受极限，解析热耐受性状背后的可遗传变异，对于理解物种应对气候变化的适应潜力至关重要。本研究以大鳞大麻哈鱼（Oncorhynchus tshawytscha）的一个自然种群为研究对象，通过全因子育种设计构建家系，并测定各亲本家系子代的心脏功能热性能及临界热最大值（CTmax），以此解析该种群热耐受性状的进化潜力。子代表型的加性遗传变异整体可忽略不计，但直接遗传效应可解释静息心率（fH）53%的表型变异。与之相反，母体效应对静息fH、心率幅度、心律失常温度及CTmax均具有显著影响。上述母体效应与卵粒大小密切相关，母本平均卵径与子代热耐受性状间的显著关联便可佐证这一点。由于大鳞大麻哈鱼的卵粒大小具有较高的可遗传性，本研究结果表明，卵粒大小带来的母体效应属于间接遗传效应，可对热耐受性状产生贡献。这类间接遗传效应可加速物种对升温带来的选择压力的进化响应，同时也可为近期在太平洋鲑鱼种群中发现的种群特异性热耐受性状提供解释。