Heating up parasitoid–host interactions: High temperature increased mortality of late‐instar braconid larvae and reduced ladybird recovery rate

Abstract With ongoing climate change, temperature‐dependent outcomes of host–parasitoid interactions can affect ecosystem functioning and key ecosystem services such as biological control. However, most studies addressing the impacts of temperature on host–parasitoid systems are biased towards immature host stages and agricultural pests, specifically Lepidoptera. Moreover, despite their relevance for population dynamics, important life‐history traits such as host recovery (i.e. restoring feeding and mating behaviour after parasitism) remain largely neglected. In this study, we tested the effects of low (18°C), optimal (24°C) and high (30°C) temperatures on the development, survival and body size of the braconid parasitoid Dinocampus coccinellae and longevity and recovery probability of its adult host, the invasive ladybird Harmonia axyridis . At low temperature, control ladybirds lived significantly longer than ladybirds exposed to Dinocampus coccinellae , and susceptible ladybirds, in which parasitoid larvae successfully developed, lived significantly shorter than resistant ladybirds, which likely eliminated parasitoid eggs. At optimal temperature, host survival was mainly determined by parasitoid development, as resistant and control ladybirds lived similarly long and susceptible individuals lived significantly shorter. At high temperatures, all ladybirds exposed to the parasitoid lived significantly shorter than control ones. Temperature significantly affected stage‐specific mortality of parasitoids, with significantly higher proportion of late‐instar larvae dying at high temperature. This together with increased pupal mortality resulted in inability of Dinocampus coccinellae to complete development at 30°C. Ladybird recovery was significantly affected by temperature, host sex and their interaction, showing highest values at optimal temperature for both sexes, but significantly decreased male recovery at low temperature. In addition, host sex influenced parasitoid body size: Female ladybirds produced larger adult wasps. The combined effects of high temperatures and parasitism negatively affected host life‐history traits, with extreme temperatures also mediating cascading effects on its braconid endoparasitoid. We demonstrate how temperature‐ and stage‐specific parasitoid mortality can influence host longevity and the understudied recovery probability, focussing on an adult beetle host, providing novel information for climate change ecology of host–parasitoid interactions. Read the free Plain Language Summary for this article on the Journal blog.