A positive genetic correlation between hypoxia tolerance and heat tolerance supports a controversial theory of heat stress

We used quantitative genetics to test a controversial theory of heat stress, in which animals overheat when the demand for oxygen exceeds the supply. This theory, referred to as oxygen- and capacity-limited thermal tolerance, predicts a positive genetic correlation between hypoxia tolerance and heat tolerance. We demonstrate the first genetic correlation of this kind in a model organism, Drosophila melanogaster. Genotypes more likely to fly under hypoxic stress (12% O2) were also more likely to fly under heat stress (39°C). This finding prompts new questions about mechanisms and limits of adaptation to heat stress.本研究借助数量遗传学（quantitative genetics）方法，检验了一项颇具争议的热应激理论：当机体对氧气的需求超出供给时，动物便会出现过热症状。该理论被称为氧气与容量限制型热耐受理论（oxygen- and capacity-limited thermal tolerance），其预测低氧耐受与热耐受之间存在正向遗传相关。本研究在模式生物黑腹果蝇（Drosophila melanogaster）中首次证实了此类遗传相关：在低氧胁迫（氧气浓度12%）下更易飞行的基因型，在热胁迫（39℃）下同样更易飞行。这一发现为热应激适应的机制及其极限带来了新的科学问题。