Simulated extreme high temperatures alter the demographic parameters of Aphelinus asychis and diminish parasitoid fitness

Abstract

Extreme high temperatures (EHTs) are predicted to increase in both amplitude and frequency with future climate warming, and severely impact the fitness of beneficial species. However, little is known about the impact of shifts in the amplitude and frequency of EHTs on the fitness and demography of parasitoids. In this study, we constructed four EHT regimes simulating EHTs of two different amplitudes (34 or 38 °C peak temperature) and frequencies (one or five peak temperature days every ten days), and investigated how these EHT regimes affected the fitness and life table parameters of Aphelinus asychis Walker (Hymenoptera: Aphelinidae) when parasitizing and feeding on the pea aphid, Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae). When A. asychis experienced a large amplitude and/or high frequency of EHTs, its development time was significantly prolonged, and key life history traits (adult longevity, host feeding events, and fecundity) were negatively affected. Moreover, as the amplitude and frequency of EHTs increased, the parasitoid's intrinsic rate of increase (r) also decreased. Overall, our results suggest that increasing the amplitude and frequency of EHTs would diminish A. asychis fitness and hinder its population growth, with potentially detrimental effects on its efficiency as a biological control agent of aphid populations under future climate scenarios.