Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Geelong 3216, VIC, Australia.
South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria, 0001, South Africa.
Sci Rep. 2023 Oct 25;13(1):18297. doi: 10.1038/s41598-023-45291-0.
Under climate change, increasing air temperature average and variability pose substantial thermal challenges to animals. While plasticity in thermoregulatory traits could potentially attenuate this impact, whether thermal acclimatisation can occur quickly enough to track weather variability in hot climates is unknown in any endotherm, and sex differences have never been tested. We investigated acclimatisation responsiveness of male and female wild zebra finches to short-term (< 2 weeks) summer temperature fluctuations in the Australian desert. Hotter weather before respirometry trials triggered a typical acclimatisation response (especially at chamber temperature T ≥ 40). However, acclimatisation occurred remarkably rapidly: metabolic rate responded within just one day, while body temperature (T) and evaporative cooling capacity (EHL/MHP) were best predicted by weather on the trial day; whereas evaporative water loss responded more slowly (1 week). Nonetheless, rapid acclimatisation only occurred in males, and females had higher T and lower EHL/MHP than males, potentially increasing hyperthermia risk. Furthermore, acclimatisation did not translate into greater acute heat tolerance (i.e. ability to tolerate T = 46 °C). Our results therefore reveal surprisingly rapid acclimatisation and even anticipatory adjustments to heat. However, with no changes in acute heat tolerance, and in females, phenotypic flexibility may provide only limited buffering against the detrimental impact of heatwaves.
在气候变化下，空气温度平均值和变异性的增加给动物带来了巨大的热挑战。虽然热调节特征的可塑性可能会减轻这种影响，但在任何恒温动物中，热驯化是否能够足够快地适应炎热气候中的天气变化，以及是否存在性别差异，这些问题都尚不清楚。我们研究了野生斑胸草雀雄性和雌性对澳大利亚沙漠短期（<2 周）夏季温度波动的适应反应。在呼吸代谢测量试验之前，更热的天气会引发典型的适应反应（尤其是在腔室温度 T≥40°C 时）。然而，适应反应发生得非常迅速：代谢率在仅仅一天内就有反应，而体温（T）和蒸发冷却能力（EHL/MHP）则由试验当天的天气预测得最好；而蒸发失水的反应则较慢（1 周）。尽管如此，快速适应仅发生在雄性中，而雌性的 T 比雄性高，EHL/MHP 比雄性低，这可能增加了过热的风险。此外，适应并没有转化为更高的急性耐热能力（即耐受 T=46°C 的能力）。因此，我们的研究结果揭示了令人惊讶的快速适应，甚至是对热的预期性调整。然而，由于急性耐热能力没有变化，而且在雌性中，表型灵活性可能只能对热浪的不利影响提供有限的缓冲。
