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，对于理解物种适应气候变化的潜力至关重要。本研究针对奇努克鲑鱼（大鳞大麻哈鱼，*Oncorhynchus tshawytscha*）种群的进化潜力展开探究，采用全因子育种设计，测定了各家系子代的心脏功能热性能以及临界热极限（critical thermal maximum，CTmax）。尽管子代表型的加性遗传变异整体可忽略不计，但这类直接遗传效应可解释53%的静息心率（fH）表型变异。与之相反，母体效应对静息心率、心率潜能、心律失常温度以及CTmax均具有显著影响。这类母体效应与卵径密切相关，母体平均卵径与子代热耐受性状间存在极强的相关性，这一结果可佐证上述关联。鉴于奇努克鲑鱼的卵径具有较高的可遗传性，本研究结果表明，卵径介导的母体效应属于一种可促进热耐受性状形成的间接遗传效应。此类间接遗传效应可加快物种应对升温选择压力的进化响应速率，同时也有助于解释近期在太平洋鲑鱼种群中发现的种群特异性热耐受差异。