Sex-specific responses to warming: A longitudinal study linking life-history variation to telomere dynamics,...

Understanding how climate warming reshapes animal life histories is crucial for assessing population persistence and evolutionary trajectories. This is particularly important in ectotherms, whose physiology, performance and, ultimately, fitness are strongly influenced by environmental temperature. Because climate warming can alter key life-history traits such as growth and survival, its effects may differ between sexes, potentially generating divergent organismal responses and long-term consequences. Identifying the mechanisms underlying these sex-specific patterns is therefore essential for explaining how ectotherms cope with warming environments. To determine whether climate warming induces sex-specific life-history responses and to elucidate physiological mechanisms underlying these responses, we conducted a longitudinal experiment in which toad-headed agamas (Phrynocephalus przewalskii) were exposed to simulated higher temperatures under seminatural conditions. We specifically monitored growth, survival, telomere dynamics, telomerase expression and oxidative status throughout development. Males exposed to elevated temperatures showed accelerated growth and a slight reduction in survival, whereas females showed no detectable changes in growth or survival. This suggests divergent sex-specific responses in life history to warming. At the physiological level, warming did not lead to telomere shortening; instead, the telomere length increased over time in both sexes. This was accompanied by a transient up-regulation of telomerase expression in rapidly growing males, which could contribute to the maintenance of the telomere during accelerated growth. However, telomerase expression declined at the end of the experiment in both sexes exposed to warming. Finally, warming increased lipid oxidative damage in both sexes despite activation of antioxidant responses at elevated temperatures. Our results show that climate warming can reshape sex-specific life-history trajectories without necessarily inducing telomere shortening, challenging the expectation that faster growth under thermal stress is inevitably associated with telomere erosion. However, warming can still impose physiological costs with potential long-term consequences for organismal health, as indicated by elevated oxidative damage. Our findings highlight the importance of integrating sex-specific life-history responses with physiological mechanisms to improve predictions of species responses to climate change.