Significance of Temperature-Rearing Conditions for Shaping the Responses of an Aphid Parasitoid Under Thermal Stress

A key aspect of climate change’s impact on organisms lies in understanding their ability to adapt to shifting and stressful environmental conditions. Insects, such as parasitoid wasps are particularly vulnerable due to limited heat tolerance. Adaptive strategies during mass rearing may enhance the efficacy and resilience of commercially reared biocontrol agents. This study assessed the effects of constant and fluctuating temperature regimens across four generations of mass-reared aphid parasitoids, examining their fitness traits and parasitism success under three thermal environments: colder [10°C], standard [20°C], and heat stress [28°C]. Parasitoids reared under fluctuating temperatures [day/night: 25°C /17°C] showed increased parasitism, but reduced progeny survival compared to those reared at a constant temperature [20°C]. Fluctuating regimens encouraged greater parasitism under heat stress, whereas constant regimens yielded intermediate parasitism across thermal environments, reflecting an evolutionary pattern consistent with the specialist-generalist trade-off. These findings underscore the value of evolutionary responses in developing adaptive rearing strategies that more accurately simulate field conditions, improving the performance of augmentative biological control under climate stress. Future research involving diverse fluctuating temperature regimes should deepen our understanding of trait trade-offs, such as survival and fecundity, and aid in identifying optimal thermal profiles to maximize resilience and efficacy in parasitoid wasps.