Differential thermal tolerance across life stages under extreme high temperatures crossed with feeding status in corn leaf aphid

Abstract

1. Climate change is expected to increase the frequency and duration of extreme heat events, which would pose significant challenges to most ectotherm species, such as insects.2. In the study, we address the thermal tolerance of corn leaf aphid, Rhopalosiphummaidis (Hemiptera: Aphididae) under brief extreme high‐temperature events (i.e. heat waves) across life stages. Immature instars and adults of R. maidis were exposed to heat events of increasing temperatures (0.5 °C min−1), starting at 22 °C and reaching one of the selected maximal temperatures (from 38.5 to 44.5 °C with an increased interval of 0.5 °C). In each temperature regime, the mortality of R. maidis was compared with and without barley seedlings.3. Results showed that the critical high temperature (CHT) of R. maidis was 39.0 °C in no feeding treatments, while it was 39.5 °C in feeding treatments. The upper lethal temperatures (ULTs) of R. maidis were significantly different between feeding and no feeding treatments. In addition, the ULTs varied significantly across life stages with the highest ULT values for 4th instars. Feeding significantly increased the thermal tolerance of phytophagous insects.4. Variable balances in plant‐herbivore interactions will be induced according to the insect feeding diet status and instar stage when experiencing extreme temperatures resulting from the warming climate. The findings will provide valuable information for understanding the role of food intake in thermal adaptation of small arthropods to extreme high‐temperature events under climate change.