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

Abstract

As temperatures are rising globally, the survival of organisms depends on their tolerance of such rising temperatures as well as resistance to indirect effects such as resource shortage under these new conditions. Genetic background and phenotypic plasticity in the form of acclimation are known to affect stress resistance, 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 stress tolerance (heat tolerance and starvation resistance). We test the beneficial acclimation hypothesis and how it is influenced by intraspecific differences. For this, we reared Glanville fritillary butterfly larvae originating from Finland and Spain at high and control temperatures, and measured their heat tolerance and starvation resistance. To assess potential costs of acclimation we also measured lifespan under control conditions. Neither adult heat tolerance nor starvation resistance were impacted by thermal conditions during development and thus we found no evidence for the beneficial acclimation hypothesis. Heat tolerance also did not differ between sex or population of origin. In contrast, we found interacting effects of population and sex on adult starvation resistance, with Spanish females outperforming other groups. Spanish females also had a longer lifespan under control conditions. Our study provides no evidence for the beneficial acclimation hypothesis but highlights the importance of population differences in stress tolerance.