Heat stress and host-parasitoid-endosymbiont interactions: Developmental timing and physiological mechanisms of thermal mismatch

热浪和其他极端气候事件正变得越来越普遍。热浪可能会破坏昆虫宿主与其天敌之间的生态相互作用，包括拟寄生虫（寄生于其他昆虫的昆虫）。拟议中的研究利用实验室、温室和田间实验来确定热浪如何改变一种农业害虫——烟草角虫（Tobacco Hornworm Manduca sexta）；其主要天敌为寄生蜂小寄生蜂；以及一种特殊的寄生病毒操纵寄主的生理和发育。这些研究验证了热浪的发育时间可以产生广泛的生态结果的假设，包括成功寄生和宿主死亡，寄主获救和存活到成年的寄生蜂和病毒死亡，以及通过产生异常巨大和长寿的毛虫来抑制病毒。这些研究还将量化热浪对这种寄主-拟寄生虫相互作用的影响如何改变其烟草寄主植物的消耗，以及对寄主植物存活和种子生产的影响。这些研究将提供详细的实验分析，说明热浪如何破坏宿主-寄生虫的相互作用，并导致广泛（但可预测的）生态后果。由于拟寄生虫是许多昆虫的主要天敌，而且拟寄生虫广泛应用于重要农业害虫的生物防治，因此了解热浪对寄主-拟寄生虫相互作用的影响对于预测气候变化对农作物及其害虫的影响至关重要。该项目继续向K-12和成人学习者推广项目，包括动手科学活动。极端气候事件可能对宿主、寄生虫和内共生体特别重要，因为它们生命阶段的发育时间往往错综复杂地交织在一起。寄主、寄生虫和共生体之间的生理差异如何影响它们在整个生命周期中对热事件的反应，并决定物种在复杂热环境中相互作用的生态结果？提出的研究使用一个模型系统来解决这些问题，该模型系统涉及一种重要的农业害虫及其主要控制剂：草食性昆虫宿主Manduca sexta；其专科小蜂寄生蜂Cotesia congregata；以及拟寄生虫的内共生多dna病毒ccbrbrovirus （CcBV）。本研究采用综合的实验室、温室和田间实验来探索这样一种假设：根据发育时间的不同，短时间的亚致死热应激事件可以对被寄生的毛虫产生广泛的结果——从成功的黄蜂羽化和宿主死亡，到完全的黄蜂死亡、异常的宿主表型，甚至成功的宿主变态（“宿主拯救”）。这些研究将：A)确定寄生后热休克的发育时间如何改变病毒的基因表达；黄蜂的生长、发育和存活；免疫反应，发育生理学，以及寄主毛虫的成功；B)评估早期热休克是否能拯救被寄生的毛虫寄主；C)量化寄生和热休克如何改变毛虫寄主的食草性，及其对寄主成功的影响；D)利用试验田花园量化热环境变化和热事件，并记录它们对热生理、黄蜂羽化和寄主成功的影响。该奖项由生物学理事会综合有机体系统部门的综合生态生理学和共生、防御和自我识别项目支持。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Heat waves and other extreme climatic events are becoming increasingly common. Heat waves may disrupt the ecological interactions between insect hosts and their natural enemies, including parasitoids (insects that are parasites of other insects). The proposed studies use lab, greenhouse and field experiments to determine how heat waves alter the interactions between an insect agricultural pest, the Tobacco Hornworm Manduca sexta; its main natural enemy, the parasitoid Cotesia congregata; and a specialized symbiotic virus of the parasitoid that manipulates the physiology and development of the host. The studies test the hypothesis that the developmental timing of heat waves can generate a wide range of ecological outcomes, including successful parasitism and host death, parasitoid and viral death with host rescue and survival to adulthood, and suppression of the virus with production of abnormally large and long-lived caterpillars. The studies will also quantify how effects of heat waves on this host-parasitoid interaction alter hornworm consumption of its Tobacco hostplant, and the consequences for hostplant survival and seed production. These studies will provide a detailed experimental analysis of how heat waves can disrupt host-parasite interactions and result in a wide (but predictable) range of ecological outcomes. Because insect parasitoids are the major natural enemies of many insects, and parasitoids are widely used in biocontrol of important agricultural pests, understanding the consequences of heat waves for host-parasitoid interactions is critical for predicting effects of climate change on agricultural crops and their pests. The project continues outreach projects to both K-12 and adult learners, including hands-on science activities. Extreme climatic events may be of particular importance for hosts, parasites and endosymbionts, because the developmental timing of their life stages is often intricately intertwined. How do physiological differences among hosts, parasites and symbionts affect their responses to thermal events throughout the life cycle, and determine the ecological outcomes of species interactions in complex thermal environments? The proposed studies address these questions using one model system, involving an important agricultural pest and its major control agent: the herbivorous insect host, Manduca sexta; its specialist Braconid wasp parasitoid, Cotesia congregata; and the parasitoid’s endosymbiotic polydnavirus, CcBracovirus (CcBV). The proposed studies use an integrated set of lab, greenhouse and field experiments to explore the hypothesis that, depending on developmental timing, short sublethal heat stress events can produce a wide range of outcomes for parasitized caterpillars—from successful wasp emergence and host death, to complete wasp mortality, abnormal host phenotypes, and even successful host metamorphosis (‘host rescue’). These studies will: A) determine how developmental timing of heat shocks following parasitization alters gene expression of the virus; growth, development and survival of the wasp; and immune responses, developmental physiology, and success of the host caterpillar; B) evaluate whether early heat shocks can rescue caterpillar hosts from parasitization; C) quantify how parasitization and heat shock alter herbivory by caterpillar hosts, and its consequences for hostplant success; D) use experimental field gardens to quantify thermal environmental variation and heat events, and document their consequences for thermal physiology, wasp emergence and host success.This award was supported by the Integrative Ecological Physiology and the Symbiosis, Defense and Self-recognition programs in the division of Integrative Organismal Systems, Biology Directorate.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.