Research Interests
Ecologists and evolutionary biologists have come to the realization that single species or two-species interactions are often not sufficient to understand the selective forces acting on organisms' traits or strategies. In my research, I have integrated studies of plant-herbivore and plant-pollinator interactions to arrive at a more complete understanding of how multiple species select on phenotypic traits such as plant secondary chemistry. My approach has combined novel techniques and experimental manipulations in the field with greenhouse and laboratory experiments to dissect aspects of this complex empirical question.
Specific projects include:
A. The ecological significance of toxic
nectar
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The perennial vine Carolina jessamine, or Gelsemium sempervirens, contains alkaloids in all plant parts including nectar. We are currently examining the consequences of "toxic nectar" for plant fitness via effects on pollinators such as this bumblebee, Bombus bimaculatus, and nectar robbers like the carpenter bee, Xylocopa virginica. We are also asking whether traits that make plants attractive to pollinators also make them more susceptible to nectar-robbing, and whether nectar-robbing decreases plant fitness. |
B. Alkaloid uptake in hemiparasitic plants
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Photo taken by W.D. Bransford; courtesy of the Lady Bird Johnson Wildflower Center |
Indian paintbrush is a parasitic plant that obtains some of its nutrients and water from host plants. Parasitic plants can also obtain defensive compounds from their hosts. In this picture, the Indian paintbrush Castilleja indivisa is obtaining alkaloids from the native host Texas bluebonnet (Lupinus texensis). |
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We have grown Indian paintbrush with high-alkaloid and low-alkaloid near-isogenic lines of the host Lupinus albus in the field to determine how alkaloid uptake affects herbivory, pollination and seed production of Indian paintbrush. Alkaloid uptake reduced herbivory, increased pollinator visits, and resulted in 50% higher lifetime seed production. Thus, alkaloid uptake has important consequences for plant fitness via interactions with pollinators as well as herbivores. |
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We are currently growing Indian paintbrush with high-alklaoid and low-alkaloid lines of L. albus in the greenhouse to determine whether alkaloid uptake influences production of iridoid glycosides, the endogenous secondary compounds of Indian paintbrush. This work is in collaboration with Katy Prudic of the University of Colorado at Boulder. |
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The plume moth Platyptilia pica consumes fruit and seeds of another Indian paintbrush species, Castilleja miniata. When C. miniata obtain alkaloids from the host Lupinus argenteus, seed predation is reduced in the field. This picture shows a plume moth larva on the Indian paintbrush, C. rhexifolia. |
C. Host preference in parasitic plants
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Haustoria are organs specific to parasitic plants that enable them to penetrate roots or shoots of their hosts. Haustoria are often induced in response to chemical cues from host plants. Here we see two haustoria forming on the root of Triphysaria pusilla, or owl's clover, in response to cues from roots of the grass host Bromus carinatus. We are examining sources of variation in host preference in Triphysaria, including the effect of maternal host on offspring host preference. This work is in collaboration with John Yoder of the University of California at Davis. |
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Research Interests |