New avenues in insect heat tolerance: towards an integrative understanding of climate change responses

In nature, insect vulnerability to temperature fluctuations is shaped by the frequency, duration, and intensity of microclimatic heat stress they experience, together with their capacity to endure such stress, broadly referred to as heat tolerance. Heat tolerance is the outcome of several physiological processes that induce injury that may ultimately lead to whole-organismal failure and death, and processes counteracting this and facilitating the repair from or prevention of heat injury. This perspective summarizes recent findings and highlights several potentially fruitful avenues through which a more holistic understanding of insect heat stress responses can be achieved. We are of the opinion that further study of mitochondrial mechanisms beyond the classic 'powerhouse' paradigm, including a deeper assessment of autophagy flux, may bring fresh insights to several outstanding research questions in insect evolutionary physiology. We therefore call for: i) integration across molecular mechanisms when testing theories of heat tolerance, ii) adopting standardized, transparent approaches across insect taxa (and life-stages) that will facilitate comparative analyses, and iii) a broader integration of experimental assessments of insect heat tolerance within the context of experienced microclimatic conditions.