Cross-tolerance evolution driven by selection on heat tolerance in Drosophila subobscura

The evolution of heat tolerance is a crucial mechanism for the adaptive response to global warming, but it depends on the genetic variance carried by populations and on the intensity of thermal stress in nature. Experimental selection studies have greatly benefited research into heat tolerance, providing valuable insights into its evolutionary process. However, the impact of varying levels of heat stress intensity on the associated changes in resistance traits has not yet been explored. Here, the correlated evolution of increasing knockdown temperature in Drosophila subobscura was evaluated on the knockdown time at different stress temperatures (35, 36, 37, and 38 {degrees}C), thermal death time (TDT) curves, and desiccation and starvation resistance. The selection of heat tolerance was performed using different ramping temperatures to compare the impact of heat intensity selection on resistance traits. Correlated evolution was found for these four resistance traits in D. subobscura, indicating that the evolutionary response to tolerance of higher temperatures also confers the ability to tolerate other stresses such as desiccation and starvation. However, these correlated responses depended on the intensity of thermal selection and sex, which may limit our ability to generalize these results to natural scenarios. Nevertheless, this study confirms the value of the experimental evolutionary approach for exploring and understanding the adaptive responses of natural populations to global warming.