Credit of issue cover: A colourful illustration of fish. Credit: BentlyChang/iStock.
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Abstract: Environmental variability and variability among individuals are inherent to nearly all biological systems, yet these forms of variability have been somewhat overlooked by comparative physiologists. Disciplines such as ecology and evolutionary biology have long embraced the complexity of natural systems and the attendant variability. Yet, for decades, many physiologists have laboured under ‘The Tyranny of the Golden Mean’—trying to minimize variation both in experimental design and data analysis to better see overarching patterns, but potentially obscuring important findings in the process. To better predict and understand organismal responses in the wild, researchers are increasingly incorporating environmental variability into laboratory experiments while also adopting more sophisticated statistical methods. Our intent in assembling this theme issue, which arose from a Society for Experimental Biology Symposium held in 2024, is to highlight advances in this burgeoning research area and provide a go-to resource for researchers interested in variability in comparative animal physiology. In this introduction, we summarize the state of variability research to-date, contextualize the articles in this special issue and highlight fruitful paths forward in the field of variability research.