Phenotypic plasticity in thermal tolerance in the Glanville fritillary butterfly

•This paper analyses thermal tolerance in the Glanville fritillary butterfly.•Comparison between two butterfly populations is done.•Thermal tolerance is related to population, gender and acclimation.•hsp70 expression after acclimation differs between the two populations.•Phosphoglucose isomerase (Pgi) gene is associated with heat knock-down time.

Ambient temperature is an ubiquitous environmental factor affecting all organisms. Global climate change increases temperature variation and the frequency of extreme temperatures, which may pose challenges to ectotherms. Here, we examine phenotypic plasticity to temperature and genotypic effects on thermal tolerance in the Glanville fritillary butterfly (Melitaea cinxia). We found no significant difference in heat or cold tolerance in populations originating from a continental climate in China and from Finland with moderate temperature variation. Acclimation to large-amplitude temperature variation increased heat tolerance in both populations, but decreased cold tolerance and increased hsp70-2 expression in the Chinese population only. The latter result indicates a genotypic effect in the response to temperature variation. In the Finnish population, a non-synonymous SNP in the phosphoglucose isomerase (Pgi) gene was associated with heat knock-down time.