Continuous heat waves change the life history of a host-feeding parasitoid

Abstract

The frequency and duration of heat waves are expected to increase under global warming, so parasitoids could increasingly encounter heat waves at some stage of their life cycle. However, few studies have focused on how host-feeding parasitoids respond to heat waves. We investigated how the frequency of heat waves during different developmental stages (larva, pupa and adult) of a host-feeding parasitoid, Eretmocerus hayati, affects its life history traits and life table parameters. The results showed that when continuous heat waves were experienced during a single stage, the development time of the stage that encountered the heat waves (either the larval or pupal stage) was significantly prolonged, while one heat wave did not have the same effect. Regardless of which stage (larval or pupal stage) of parasitoids encountered continuous heat waves, life history traits (host feeding, fecundity and longevity) and life table parameters (intrinsic rate of increase, r) were significantly decreased. Moreover, heat waves at the pupal stage had greater detrimental effects on adult performance than heat waves at the larval stage. However, when adult parasitoids experienced continuous heat waves, their lifetime fecundity did not differ significantly from that of parasitoids that experienced heat waves only once during a single stage. When two or three stages faced continuous heat waves, adult performance sharply decreased, especially in terms of r. Hence, these findings suggest that the timing and duration of heat waves should be assessed before releasing a parasitoid as a biological control agent. If such an assessment is not performed, the biological control efficiency could be greatly decreased.