Li Dongbo, Brough Benjamin, Rees Jasper W, Coste Christophe F D, Yuan Chenggui, Fowler Mike S, Sait Steven M
School of Biology, Faculty of Biological Sciences University of Leeds Leeds UK.
Department of Biosciences Swansea University Swansea UK.
Ecol Evol. 2024 Jul 21;14(7):e70047. doi: 10.1002/ece3.70047. eCollection 2024 Jul.
Climate change is projected to increase the frequency and intensity of extreme heat events, and may increase humidity levels, leading to coupled thermal and hydric stress. However, how humidity modulates the impacts of heat stress on species and their interactions is currently unknown. Using an insect host-parasitoid interaction: the Indian meal moth, , and its endoparasitoid wasp, , we investigated how humidity interacted with heat stress duration, applied at different host developmental stages, to affect life history traits. Hosts parasitized as 4th instar larvae and unparasitized hosts were maintained in high- (60.8% RH) or low-humidity (32.5% RH) at constant 28°C. They were then exposed to a 38°C thermal stress with a duration of 0 (no heat stress), 6 or 72 h in either the 4th or 5th host instar. Neither humidity nor heat stress duration affected emergence of unparasitized hosts, but increasing heat stress duration during the 4th instar decreased parasitoid emergence irrespective of humidity. When applied during the 5th instar, increasing heat duration decreased parasitoid emergence under low humidity, but no effect of heat stress was found under high humidity. Moreover, experiencing longer heat stress in the 4th instar increased host larval development time and decreased body size under high humidity, but this effect differed under low humidity; increasing heat duration in the 5th instar decreased parasitoid body sizes only under low humidity. Larval stage and heat stress duration directly affected parasitized host survival time, with a concomitant indirect reduction of parasitoid sizes. We show that humidity modifies key life history responses of hosts and parasitoids to heat stress in species-specific ways, highlighting the potential importance of humidity in regulating host-parasitoid interactions and their population dynamics. Finally, we emphasize that interactions between environmental stressors need to be considered in climate change research.
预计气候变化将增加极端高温事件的频率和强度，并且可能提高湿度水平，从而导致热应激和水应激同时出现。然而，目前尚不清楚湿度如何调节热应激对物种及其相互作用的影响。利用一种昆虫宿主-寄生蜂的相互作用：印度谷螟及其内寄生蜂，我们研究了湿度如何与在不同宿主发育阶段施加的热应激持续时间相互作用，从而影响生活史特征。作为四龄幼虫被寄生的宿主和未被寄生的宿主在28°C恒温下分别饲养在高湿度（相对湿度60.8%）或低湿度（相对湿度32.5%）环境中。然后，它们在宿主的第四龄或第五龄阶段暴露于38°C的热应激中，持续时间分别为0（无热应激）、6或72小时。湿度和热应激持续时间均未影响未被寄生宿主的羽化，但在四龄阶段，无论湿度如何，热应激持续时间的增加都会降低寄生蜂的羽化率。当在五龄阶段施加热应激时，热应激持续时间的增加会降低低湿度条件下寄生蜂的羽化率，但在高湿度条件下未发现热应激的影响。此外，在高湿度条件下，四龄阶段经历更长时间的热应激会增加宿主幼虫的发育时间并减小体型，但在低湿度条件下这种影响有所不同；五龄阶段热应激持续时间的增加仅在低湿度条件下会减小寄生蜂的体型。幼虫阶段和热应激持续时间直接影响被寄生宿主的存活时间，同时间接减小寄生蜂的体型。我们发现，湿度以物种特异性方式改变宿主和寄生蜂对热应激的关键生活史反应，突出了湿度在调节宿主-寄生蜂相互作用及其种群动态方面的潜在重要性。最后，我们强调在气候变化研究中需要考虑环境压力因素之间的相互作用。
