Wild parsnip, a tall invasive plant with small yellow flowers commonly found along roadsides across the Midwest, is best avoided, as chemicals on the leaves can cause blistering skin rashes. These toxic chemicals also play a critical role in defending it from plant-eating critters. The chemicals produced by wild parsnip are so potent that only a few species, such as the parsnip webworm, have co-evolved to tolerate the toxicity and feed on the plant.  

To understand how climate change is affecting the relationship between wild parsnip and the parsnip webworm, researchers, including a Midwest CASC-funded doctoral student, are examining how the co-evolved relationship has changed over the past 30 years. They began by tracking down old field sites from scientific literature and old lab notebooks at the University of Illinois to identify locations for resampling sites that were first surveyed nearly 30 years ago. The team plans to compare newly collected plant materials with archived ones, documenting changes in plant chemistry and insect infestation rates over time. 

Co-evolutionary relationships vary across landscapes, and this research will reveal how plant-insect interactions and plant chemistry respond to climate change, offering insights for biological control strategies to manage invasive species like the wild parsnip.