Pharm-Ecology of Monarch Butterflies
Our lab is interested in the medicinal properties of plants, and how animals may self-medicate by using plant secondary metabolites. We collaborate with Jaap de Roode’s lab at Emory University to study interactions between monarch butterflies, their protozoan parasites, and the milkweed plants upon which monarchs feed as larvae. Most milkweeds contain toxic steroids called cardenolides, which can help to protect monarch caterpillars and butterflies from predators. But cardenolides also serve to protect monarch caterpillars from a protozoan parasite, Ophryocystis elektroscirrha that reduces monarch fitness.
Milkweeds that are high in cardenolides increase both the resistance and tolerance of monarchs to parasite infection. As a consequence, infected female monarchs preferentially lay their eggs on high-cardenolide milkweed species.
In current work, we are exploring the ecological factors that influence milkweed chemistry, and subsequent effects on the medication behavior by monarchs. For example, we are exploring how mycorrhizal fungi in soil, and global environmental change (elevated carbon dioxide concentrations, changing patterns of precipitation), influence monarch-parasite interactions through their impacts on milkweed chemistry.
Population Dynamics in a Changing World
Global environmental change is having a substantial impact on the population dynamics of species. Using long-term data on species abundances and climatic factors, we build models to explore how animal populations may respond to our changing world. For example, in collaboration with Peter Price from Northern Arizona University, we have established that increasing drought in the southwestern United States causes substantial decreases in the populations of gall-forming sawflies on willow trees.
Similarly, in collaboration with a team of Finnish researchers, we have shown that rapid and dramatic climate change is altering an entire assemblage of moths in a sub-arctic forest in Finnish Lapland.