Volatile-Mediated Plant-to-Plant Communication and Induced Defenses
In contrast to most animals which can move to avoid predators, plants are largely immobile and consequently have evolved an impressive defense system to combat herbivores. Many plants are armed with specialized morphological structures such as thorns as well as secondary metabolites that have repellent and toxic effects on consumers. While many plant defenses are always expressed, numerous defenses are induced in response to herbivory or a perceived imminent attack, rendering the plants more resistant to subsequent attack by herbivores. This induced resistance response is triggered by the release of volatile organic compounds from damaged tissue. For example, leaves that are actively being consumed emit volatile cues that are perceived by adjacent undamaged branches allowing them to increase their defenses.
For Marie-Curie Fellowship, I explored the effects of volatile-mediated plant-to-plant communication and induced resistance among sagebrush plants. This was accomplished through field studies in the Eastern Sierra Nevada Mountains in California and environmental chamber experiments at the University of Eastern Finland. To measure plant responses, I developed behavioral assays with herbivores and molecular assays to assess the activation of defense-related genes. This work has led to several papers which have provided new insight regarding the evolution of volatile-mediated signaling and volatile-mediated passively acquired defenses. |
Protective Mutualisms and Associational Resistance
The food-for-protection mutualism between extra-floral nectar (EFN) producing plants and ants is well documented. What is not known is whether non-nectar producing companion plants benefit from this protective service. Similarly, while it is well established that parasitoids act as an indirect defense of damaged plants, it is unknown whether the presence of EFN aids in this protective benefit. I lead a team of graduate students and field technicians in Oaxaca, Mexico to answer these questions as part of a larger Swiss National Science Foundation project. Our work has promise to inform sustainable agriculture.
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Positive Facilitation via Mechanical Defenses of Plants
Associational refuges occur when one species positively facilitates a second species by providing a refuge from abiotic or biotic stress. Much research has shown that associational refuges created by plant traits mediate interactions between insects that use those plants and the predators of those insects. My research has focused on quantifying the quality of refuges provided by physical (aka mechanical) defenses of plants and linking the spatial distribution of those traits with that of the benefiting organism at the landscape scale. In one study, we found that caterpillars that selected mechanically defended thistles in which to pupate were greater than 90% more likely to avoid predation by rodents. In a second study, we found that a combination of canopy structural complexity and mechanical defenses increased the survival of molting dragonflies which are highly vulnerable to predation by birds.
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The Effects of Climatic Variation on Spatial and Population Dynamics
Insect populations are sensitive to climactic changes, but most research on climate change has been concerned with shifts in species’ ranges. Less work has been conducted studying climate effects on population dynamics and species interactions in real communities. My colleagues and I have conducted over a decade of manipulative field experiments to examine the effects of variation in precipitation and temperature on a metapopulation of tiger moths. I used these data to parameterize a patch quality metric in a metapopulation model using a long-term patch occupancy dataset. This spatially explicit model incorporated climatic variables and non-random dispersal behavior determined through a previous capture-mark-recapture study. From this total body of work comprised of eleven articles where I was the first or co-author, we showed how abiotic factors can indirectly affect local demography through changes in patch quality, which in turn alter extinction and colonization dynamics and ultimately metapopulation persistence. Our main findings demonstrated that incorporating realistic dispersal behavior in metapopulation models is necessary for accurate predictions and highlight the peril facing isolated populations existing in drought prone areas.
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