The effect of heat stress on paper wasps from different climates

In a warming world, mechanisms for coping with stressfully high temperatures are of great importance to ectotherms such as insects. Among these mechanisms is the Heat Shock Response, which aids in recovery from heat stress and increases thermal resistance. The primitively eusocial paper wasps (Polistes spp.) are found across widely varying thermal environments, showcasing their adaptability with regard to temperature. We investigated the Heat Shock Response in paper wasp adults by measuring the expression of heat shock proteins (hsp70, hsp83, hsc70) under control conditions (22-24 °C) or following a heat exposure (42 °C or 44 °C). Additionally, we measured heat stress resistance as time to knockdown. The wasps were collected from three climatic regions (Alpine, temperate, Mediterranean) and included three closely related species (P. biglumis, P. dominula, P. gallicus) to investigate if they used the Heat Shock Response differently. We found evidence of species-specific basal expression under control conditions, with the Mediterranean P. gallicus showing the highest expression. Both hsp70 and hsp83 were found to be highly responsive to heat stress. The results of the time to knockdown assay indicated a difference in both basal tolerance and in the response to heat stress between species and climates of origin. Overall, the study shows the multifunctionality of the Heat Shock Response, as the utilization differed between species depending on geographical origins. The results suggest that a quick adaptive utilization of the Heat Shock Response could be one of the physiological traits allowing paper wasp species to inhabit such widely different thermal environments.