Variation in heat shock protein expression at the latitudinal range limits of a widely‐distributed species, the G lanville fritillary butterfly ( M elitaea cinxia )

Studies of heat shock response show a correlation with local climate, although this is more often across altitudinal than latitudinal gradients. In the present study, differences in constitutive but not inducible components of heat shock response are detected among populations of the G lanville fritillary butterfly M elitaea cinxia L. that exist at the species' latitudinal range limits ( F inland and S pain). The study demonstrates that macroclimatic differences between these sites should cause greater exposure of the S panish population to higher temperatures. Thermal stress treatments are used to estimate differences in the expression of four genes potentially relevant for tolerating these temperatures. For the analysis, three heat‐shock proteins and glyceraldehyde‐3‐phosphate dehydrogenase ( G3PDH ), a glycolysis enzyme that also modulates cell growth based on metabolic state, are chosen. Two constitutive differences are found between the sites. First, insects from S pain have higher levels of Hsp 21.4 than those from F inland regardless of thermal stress treatment; this protein is not inducible. Second, insects from F inland have higher levels of G3PDH . The two remaining Hsps, Hsp20.4 and Hsp90 , show dramatic up‐regulation at higher temperatures, although there are no significant differences between insects from the different populations in either constitutive levels or inducibility. In nature, differences between the study populations likely occur in the expression of all four genes that were studied, although these differences would be directly climate‐induced in Hsp20.4 and Hsp90 and constitutive in Hsp21.4 and G3PDH . Inducibility may mitigate the need for constitutive variation in traits that adapt insects to local climate.