Ongoing global change affects both wildlife and economically relevant species, which are now subjected to combined challenges from climate change and higher exposure to pathogens. Honeybee colonies worldwide are under threat by higher temperatures and the ectoparasitic mite Varroa destructor, hence we studied the impact of these combined challenges in the thermal biology and energetics of Apis mellifera. We estimated the heat tolerance and energy expenditure (CO2 production, VCO2) of honeybees acclimated to different temperatures (32 and 38ºC) and subjected to different levels of parasitism (0, 1 and 2 mites). Heat tolerance was quantified employing thermal death time (TDT) curves describing how survival times vary as a function of temperature, which differed significantly between treatments. Warm-acclimated uninfected bees exhibited a higher thermal tolerance than their cold-acclimated counterparts, but parasitism by Varroa resulted in a substantial drop in tolerance rendering TDT curves of parasitized bees virtually indistinguishable. Accordingly, VCO2 increased dramatically in parasitized bees (46.5% and 67.1% with 1 and 2 Varroa, respectively), suggesting that Varroa impinges on substantial costs on energy expenditure which, in combination with lower fat reserves due to parasitism, should have synergistic effects on bees’ survival and performance. Results provide conclusive evidence of the detrimental impact of Varroa on heat tolerance that undermines potentially adaptive responses associated with thermal acclimation. Results also show that heat treatments are a realistic venue to control Varroa, and we discuss how TDT curves may be employed to optimize management strategies in this context.

中文翻译：

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寄生蜂的蜜蜂的耐热性、能量学和热处理

持续的全球变化影响到野生动物和经济相关物种，这些物种现在受到气候变化和病原体暴露增加的综合挑战。全世界的蜜蜂群都受到高温和外寄生螨瓦螨破坏者的威胁，因此我们研究了这些综合挑战对蜜蜂的热生物学和能量学的影响。我们估计了适应不同温度（32 和 38ºC）并受到不同程度寄生（0、1 和 2 只螨虫）的蜜蜂的耐热性和能量消耗（CO2 产生，VCO2）。使用热死亡时间 (TDT) 曲线对耐热性进行量化，该曲线描述了存活时间如何随温度而变化，温度在治疗之间存在显着差异。暖驯化的未感染蜜蜂比冷驯化的蜜蜂表现出更高的耐热性，但 Varroa 的寄生导致耐受性大幅下降，使得寄生蜜蜂的 TDT 曲线几乎无法区分。因此，寄生蜂的 VCO2 显着增加（分别为 46.5% 和 67.1%，使用 1 只和 2 只 Varroa），这表明 Varroa 影响了大量的能量消耗成本，再加上寄生导致的较低脂肪储备，应该对蜜蜂的生存和表现。结果提供了确凿的证据，证明 Varroa 对耐热性的不利影响会破坏与热适应相关的潜在适应性反应。结果还表明热处理是控制瓦螨的现实场所，