While most parts of most plants are green, those parts that are not -- from fruits and flowers to red leaves and stems -- raise ecological mysteries about how plants are communicating with animal partners and enemies alike. Plant coloration is a conspicuous and easily-scored trait that can be used to study how ecological forces shape organismal traits. Plant coloration is also frequently polymorphic within populations and variable within genera; this variation allows for robust comparisons between individuals and species with different coloration to elucidate the effect of pigment presence on a wide variety of ecological interactions simultaneously.
I have investigated these questions in work I have both lead and collaborated on. As part of my dissertation, I investigated the ecological forces acting on naturally-occurring anthocyanin loss in pitcher plants, comparing prey capture, herbivory, pollination, and colonization by specialist insect larvae, between neighboring red and green plants, finding that red morphs actually perform worse in prey capture and herbivory avoidance than green morphs, but also capture fewer of their pollinators than their green neighbors (Martin-Eberhardt, Weber, & Gilbert, 2025). In my collaborative work, I have contributed to an undergrad-lead investigation of flower color polymorphism in the invasive mustard Dame’s Rocket, revealing that purple morphs are more resistant to herbivory, but have warmer flowers and reduced pollen viability in sunny areas (Gaugan et al., in prep). I have also contributed data from my own undergraduate work to a metaanalysis on delayed greening lead by Dr. Tati Cornellissen, finding that colored (non-green) leaves were better defended, less nutritious, and experienced reduced herbivory compared to green leaves (Cornelissen et al., in review).
Plants benefit from communicating with animals in a variety of ways, from mutualistic services such as pollination, dispersal, and defense, to warning signaling such as declaring or lying about toxicity. Many plants (and other organisms) use more than one signal to send seemingly the same message; multiple signaling can have a variety of information transfer benefits that help explain investment in not one but multiple potentially costly signals.
One unique case of plant-animal signaling occurs in plant carnivory, where plants dupe arthropods into visiting their entrapping leaves. I leveraged this unique interaction to examine two mechanistic hypotheses of multiple signaling: 1) that multiple signals might increase the likelihood of response by one important receiver and 2) that each signal helps reach a different subset of receivers, thereby widening the total 'audience'. In this project using artificial pitcher plant models to independently manipulate three plant traits (color, nectar, and VOCs), I found that multiple signaling increased both the capture of a major prey item (the ant Myrmica lobifrons) and the total breadth of insects captured.
Some of my work also falls into the category of classic plant defense, including herbivore resource tracking and induced defenses. My work stems from the mystery: in resource-poor areas, why don't plants with specialized nutrient acquisition strategies such as nitrogen fixation, leaf litter capture, and carnivory take over? Because herbivores are known to track resources, they may provide an explanation: if the presence of investment in specialized nutrient acquisition strategy allows one individual or species to gather more nutrients, herbivores may preferentially attack this individual, or, over evolutionary time, switch to a species with a specialized nutrient strategy. Looking within the Purple Pitcher Plant (Sarracenia purpurea), a facultative plant carnivore, we find herbivores track resources and may create a mid-level optimal nutrient intake by preferentially attacking individuals that are highly successful at prey capture.
In addition to my work on herbivore behavior and direct impacts of herbivory, I am also interested in plant defense mutualisms, and disruptions to established mutualisms. For example, extrafloral nectaries (EFNs) can attract ants and other predatory insects that act as "pugnacious bodyguards" and reduce herbivory. However, sooty molds and other fungus often exploit this resource, and presumably interfere with the ant-plant mutualism by reducing the effectiveness of the EFN reward. One way plants might defend their nectaries from fungus are anthocyanin compounds, and indeed many EFN-bearing plants often have conspicuous red nectaries. To investigate a possible anti-fungal role of anthocyanins in EFNs, I am taking both cross-species and transgenic approaches, using herbarium specimens, living collections, a common garden, and, in collaboration with fellow graduate student Madison Plunkert, genetic transformation in a single species to interrogate this question across scales.
