EXTREME WEATHER
HEAT WAVE EVENTS
Heat waves, brief periods of unusually high temperatures, are increasing in frequency and intensity in many regions. Such extreme weather events challenge our ability to effectively manage agricultural pests because they can disrupt multi-trophic interactions that contribute to pest control. My postdoctoral research at the Wetzel Lab focuses on the effects of heatwaves on the potato (Solanum tuberosum) agricultural system. I work with Colorado potato beetle (CPB, ; Leptinotarsa decemlineata), potato (Macrosiphum euphorbiae) and green peach (GPA, Myzus persicae) aphids as the main herbivorous pest of potato crops.
Using a combination of field, greenhouse, growth chamber, and lab experiments, I ask the following questions: 1) Are the effects of heatwaves dependent on the timing of the heatwave and herbivory events? 2) How do plants regulate responses to conflicting stressors such as multiple herbivore attack and heat stress? 3) Are heatwave effects on plant-insect interactions mediated by changes in plant chemistry? |
The roles of timing and plant resistance in mediating heatwave effects on herbivorous pests
A major barrier to our ability to understand and predict the effects of a heat wave on crop-pest interactions is heat wave timing. Heat waves can impact a system at any time during a growing season, and important pests, such as insects, often have complex life cycles with metamorphosis between stages with varying physiological tolerances. A result, heat sensitivity of pests may vary across ontogenetic stages leading heat waves to have different ecological impacts at different times during the growing season.
In this experiment, I examined how heat waves and their timing interact with crop pest resistance to influence the interactions between potato crops and its most damaging pest, the Colorado potato beetle. We used open-top chambers and ceramic heaters to generate heat wave conditions in field plots with pest-resistant and -susceptible potato varieties at four CPB developmental stages (from neonates to adults) and assessed CPB performance, crop damage, and tuber yield.
Carvajal-Acosta, A. N., Luke N. Zehr, Joshua S. Snook, Zsofia Szendrei, Michael Kalwajtys, and William C. In Revision. Heat wave impacts on crop-pest interactions depend on insect ontogeny and plant resistance. Ecosphere.
In this experiment, I examined how heat waves and their timing interact with crop pest resistance to influence the interactions between potato crops and its most damaging pest, the Colorado potato beetle. We used open-top chambers and ceramic heaters to generate heat wave conditions in field plots with pest-resistant and -susceptible potato varieties at four CPB developmental stages (from neonates to adults) and assessed CPB performance, crop damage, and tuber yield.
Carvajal-Acosta, A. N., Luke N. Zehr, Joshua S. Snook, Zsofia Szendrei, Michael Kalwajtys, and William C. In Revision. Heat wave impacts on crop-pest interactions depend on insect ontogeny and plant resistance. Ecosphere.
Regulation of plant response to heat stress and multi-herbivore attack
Plants are often attacked by multiple insect herbivores, sequentially and simultaneously. However, how plants deal with attackers from multiple feeding guilds and simultaneous abiotic stress is poorly understood. The goal of this project is to investigate the mechanisms by which plants modulate responses (via phytohormones SA, JA, ABA) to multiple herbivore attackers under extreme heat stress and its impacts on multi-species interactions (i.e., crop–pest, pest–enemy, herbivore-symbionts). To do so, I conducted a field experiment, coupled with greenhouse and growth chamber experiments, where I simulated a single heat wave on potato plants attacked by either CPB or potato aphid or both herbivores simultaneously or sequentially. I then measured, herbivore response, plant direct (glycoalkaloids) and indirect defenses (HIPVs), and phytohormones to examine the mechanisms driving plant response to conflicting stressors.
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Carvajal-Acosta, A. N., Szendrei, Z., Wetzel, W. W. In preparation. Regulation of plant response to heat stress and multiple-herbivore attack in a tri-trophic agroecosystem.
Heatwave effects on top-down pest control
Parasitoids are a powerful biological tool used to control pest outbreaks. Yet, we have a limiting understanding of how herbivores and their parasitoids respond to heat stress and whether such effects are relevant for the effectiveness of biological controls. In this study, I examine the effect of heatwaves on an endo-parasitoid (Aphidius ervi), commonly used to control aphid populations. I specifically examine whether heatwaves alter (herbivore-induced plant volatiles) HIPV in potatoes and whether such changes alter the parasitoid ability to locate their host (GPA; Myrzus persicae). To answer these questions, I collected and measured plant volatiles and conducted Y-tube choice bioassays with parasitic wasps and aphid-damaged heat-stressed and non-heat stressed potato plants.
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DROUGHT EVENTS
Droughts are becoming more frequent and severe in various parts of the world due to climate change. These events pose significant challenges to natural ecosystems, disrupting intricate ecological processes and interactions critical for ecosystem health and resilience. Understanding the effects of drought on ecosystem dynamics is crucial for effective conservation and management strategies aimed at mitigating the impacts of climate change on natural systems.
Intra-specific variation in host-plant traits mediates herbivore drought response
The response of herbivorous insects to plant drought stress can range from positive to negative, and it has been challenging to understand the causes of this variation. I use the milkweed system (Asclepias genus) to understand whether plant traits associated with aridity might underlie this variation. By experimentally manipulating drought conditions, I test for evolutionary convergence between the traits of 13 milkweed species (genus Asclepias) and the indirect effects of drought stress on the performance of a leaf-chewing (monarch caterpillars; Danaus plexipus) and a sap-feeding (oleander aphid; Aphis nerii) herbivore.
Carvajal-Acosta, A. N., Agrawal, A. A., and Mooney K. A. 2022. Plant traits as mediators of herbivore drought response: phylogeny, physiology, and functional traits. Ecology.
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Drought effect on plant direct and indirect chemical defenses and consequences for herbivory
Climatic change is resetting complex coevolutionary relationship across multiple trophic levels. In particularly, drought events can alter the way herbivore impact plants by inducing changes in phytochemicals associated with direct and indirect defense. In this study, I investigate how drought stress may alter plant-herbivore-predator dynamics in the heartleaf bittercress (Cardamine cordifolia) system. To accomplish this, I simulated drought conditions on heartleaf bittercress plants subject to herbivory by chrysomelid beetles (Phaedon sp. nr. oviformis) exposed to or protected from predators and estimated leaf herbivory. To further explore whether drought-induced changes in herbivory pressures are mediated by plant chemistry, I measured glucosinolates content (the main anti-herbivore compound in Brassica) and herbivore-induced plant volatiles (HIPVs).
Carvajal-Acosta, A. N., Gloss, A., and Mooney, K. A. In preparation. Chemical Ecology of Plant-biotic interactions in a changing environment.
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CLIMATE VARIABILITY
Modeling distributional response to climate change of a specialized herbivore (Danaus plexippus)
Ecological convergence in phytochemistry and plant-insect interaction outcomes along an elevation gradient
A) Shows the elevational profile of Central Chile, with highlighted the low coastal elevational zone (pink shading), the inland elevational zone (green shading), and the Andean high elevational zone (blue shading). B) Violin plots show the elevational distribution of the seven Haplopappus species studied.
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The astonishing diversity of compounds produced by plants is thought to arise from plant's adaptation to local conditions. In this study, we investigated whether closely related species in the genus Haplopappus occupying similar niches along a gradient, converge to produce similar floral odours. We further explore whether the outcome of flower-insect visitors also converge within elevation bands by estimating the cost-benefit ratio of fertilized vs. predated seeds.
Carvajal-Acosta, A. N., Formenti, L., Godschlax, A., Katsanis, A., Mooney, K., Villagra, C., and Rasmann, S. 2023. Ecological convergence in phytochemistry and flower-insect visitor interactions along an Andean elevational gradient. Ecology & Evolution.
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