More frequent extreme high temperature events alter adult and next-generation traits in Menochilus sexmaculatus (Coleoptera: Coccinellidae)

Global climate warming is characterized by an escalation in extreme high temperatures (EHTs). While the frequency of EHTs is predicted to increase under climate change, there remains a limited understanding of whether maternal exposure to altered EHT frequencies affects maternal provisioning and next-generation phenotypic traits in insects. In this study, we investigated the influence of exposure to varying frequencies (either 1 or 5 peak-temperature days every 10 d, with a peak temperature of 34 °C) of EHTs on reproductive decisions and offspring traits in Menochilus sexmaculatus (Fabricius) (Coleoptera: Coccinellidae). Our results revealed that M. sexmaculatus females exposed to a high frequency of EHTs exhibited a decrease in fecundity, alongside an increase in the proportion of non-viable eggs. Furthermore, maternal ladybirds experiencing a high frequency of EHTs could increase their offspring's body size. Offspring reared under a high-frequency EHT treatment displayed an extended larval development period, decreased egg laying, and a higher proportion of non-viable eggs. However, egg weight, egg clutch number, and egg clutch size in both maternal and offspring generations were unaffected by the increased frequency of EHTs. Our findings indicate that increased frequency of EHTs can generate modification in both maternal and offspring phenotypic traits, suggesting that adaptation to such conditions may occur through maternal effects. This research represents an essential step toward understanding the impact of maternal effects on the phenotypic traits of M. sexmaculatus in response to varying frequencies of EHTs and may further enhance our understanding of M. sexmaculatus population dynamics under future climate scenarios.