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Synopsis In response to rapidly changing environmental conditions, many organisms are experiencing shifts in geographic ranges and in the timing and expression of key life-history traits, which have important effects on fitness. However, the physiological mechanisms that mediate these phenotypic responses, such as endocrine and other signaling pathways are not well understood. This information will be critical for predicting organismal responses to climate change because physiological mechanisms are often highly responsive to environmental cues and influence the phenotypic variation available to selection. Additionally, they often integrate suites of correlated traits and are thus expected to influence the evolutionary response to selection. The overarching goals of this symposium were to gain novel insights into the physiological mechanisms that underlie organismal responses to rapidly changing environmental conditions and to identify gaps in knowledge and experimental approaches to advance the field. Here we review and discuss the symposium contributions and the research themes that emerged as important foci for future studies. 

Stress can influence lifespan in both positive and negative ways, depending on exposure intensity and duration. However, mechanisms driving positive stress effects on lifespan remain poorly understood. Prolonged hypoxia extends the lifespan of overwintering prepupal Megachile rotundata. Here, we explore telomere length and reduced oxidative stress as potential mechanisms of this extended lifespan. We hypothesized high antioxidant capacity under hypoxia reduces oxidative damage and telomere loss. We exposed prepupae to 10, 21 or 24% oxygen for up to 9 months and measured monthly survival, telomere length, antioxidant capacity, and lipid peroxidation across treatment duration for prepupae and adults. After 9 months of exposure, survival was highest in hypoxia and lowest in hyperoxia. Telomere length did not differ among oxygen treatments but increased in adults compared to prepupae. Total antioxidant capacity and lipid peroxidation showed no significant differences among oxygen treatments, suggesting compensatory responses to maintain baseline oxidative levels.