Aerobic performance is tied to fitness as it influences an animal’s ability to find food, escape predators, or survive extreme conditions. At high altitude, where low O₂ availability and persistent cold prevail, maximum metabolic heat production (thermogenesis) is an aerobic performance trait that is closely linked to survival. Understanding how thermogenesis evolves to enhance survival at high altitude will yield insight into the links between physiology, performance, and fitness. Recent work in deer mice (Peromyscus maniculatus) has shown that adult mice native to high altitude have higher thermogenic capacities under hypoxia compared with lowland conspecifics, but that developing high-altitude pups delay the onset of thermogenesis. This finding suggests that natural selection on thermogenic capacity varies across life stages. To determine the mechanistic cause of this ontogenetic delay, we analyzed the transcriptomes of thermoeffector organs—brown adipose tissue and skeletal muscle—in developing deer mice native to low and high altitude. We demonstrate that the developmental delay in thermogenesis is associated with adaptive shifts in the expression of genes involved in nervous system development, fuel/O₂ supply, and oxidative metabolism pathways. Our results demonstrate that selection has modified the developmental trajectory of the thermoregulatory system at high altitude and has done so by acting on the regulatory systems that control the maturation of thermoeffector tissues. We suggest that the cold and hypoxic conditions of high altitude force a resource allocation tradeoff, whereby limited energy is allocated to developmental processes such as growth, versus active thermogenesis, during early development.

中文翻译：

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基因调节的适应性变化是高海拔鹿小鼠生热发育延迟的基础。

有氧运动与健身息息相关，因为它影响动物寻找食物，逃避食肉动物或在极端条件下生存的能力。在高海拔地区，普遍存在O ₂利用率低和持续感冒的情况，最大的代谢热产生（产热）是一种有氧运动性能，与生存密切相关。了解生热作用如何演变以提高高海拔生存率，将使人们深入了解生理，机能和适应性之间的联系。鹿小鼠的最新研究（Peromyscus maniculatus）已显示，与低地同种动物相比，高海拔地区的成年小鼠在低氧条件下具有更高的生热能力，但发育中的幼崽延迟了生热的发生。这一发现表明，生热能力的自然选择在生命的各个阶段都不同。为了确定这种个体发育延迟的机制原因，我们分析了低海拔和高海拔本地发育中的鹿小鼠中热效应器官（棕色脂肪组织和骨骼肌）的转录组。我们证明，生热的发展延迟与参与神经系统发育，燃料/ O ₂的基因表达的适应性转变有关供应和氧化代谢途径。我们的结果表明，选择已经改变了高海拔温度调节系统的发展轨迹，并且通过作用于控制热效应组织成熟的调节系统来实现。我们建议高海拔地区的寒冷和低氧条件迫使资源分配权衡，从而在早期开发过程中将有限的能量分配给诸如生长的发育过程，而不是活跃的生热作用。