Data for: Clear effects of population and sex but not rearing temperature on stress tolerance in a temperate butterfly

With temperatures rising globally due to climate change, an organism’s survival depends both on its direct tolerance to rising temperatures and its tolerance to indirect effects of warming, such as resource shortage. Genetic background and phenotypic plasticity in the form of acclimation are known to affect stress tolerance, but much about genetic variation in plasticity is still unknown, especially in insects other than Drosophila. Here we aim to study the effect of population of origin, developmental temperature, and their interaction on heat and starvation tolerance. We test the beneficial acclimation hypothesis and how it is influenced by intraspecific differences. For this, we reared Glanville fritillary butterfly (Melitaea cinxia) larvae originating from Finland, where the climatic conditions experienced are relatively cool, and Spain, where the climate is relatively warm, at high and standard temperatures. In the adult stage, we measured stress tolerance as the time until heat knockdown at a constant 45 °C and lifespan under resource limitation. To assess other effects of thermal acclimation, we also measured performance traits such as larval developmental time, survival, and adult lifespan. We found no significant effect of rearing temperature on heat or starvation tolerance, and heat tolerance also did not differ directly between sex or population of origin. In contrast, we found interacting effects of population and sex on adult starvation tolerance, with females originating from Spain outperforming other groups. Spanish female butterflies also had a longer lifespan under non-stressful conditions, and we found significant GxE interactions in other performance traits. Even though our study provides no clear evidence for the beneficial acclimation hypothesis, it highlights the importance of considering population and sex differences in stress tolerance. Recognising these differences will help to fine-tune and prioritise conservation efforts.