December 18, 2024

Anyone who has brushed against wild parsnip while on a hike knows to be wary of the tall plant and its little yellow flowers. For the uninitiated: wild parsnip, an invasive weed from Europe that can be found on roadsides and other disturbed areas across the Midwest, can cause a painful, blistering rash when it comes into contact with skin. 

Wild parsnip also has a unique relationship with the parsnip webworm, which exclusively feeds on the plant. Lance Jones, MW CASC-funded doctoral student working with May Berenbaum at the University of Illinois Urbana-Champaign, is studying the relationship between these two species specifically in the context of climate change. Using archived material, field work, and plant chemistry, Jones and the Berenbaum lab team are trying to understand the last 30 years of change in this model system. 

Research Goals 

The Berenbaum lab is very interested in chemical ecology, including the interactions between plants and insects. In short, plants produce chemical responses in reaction to insect actions like herbivory. Insect species in turn can adapt to these compounds over long periods of time and a very interesting interplay through coevolution takes place. In some cases – such as the wild parsnip and the parsnip worm – a plant that is particularly toxic may only have a small number of insect species that are capable of eating it. 

The lab has studied the wild parsnip-parsnip worm system for more than 40 years. But how is this system coping with climate change and loss of winter? No one knows – yet. 

The team is in the process of resampling populations of these plants and their insects that were first surveyed nearly 30 years ago. With an archive of plant material that's been saved since that time, the team can document the changes in plant chemistry, as well as changes in infestation rates for the insects, and compare them to what was seen decades ago. 

Jones shared his excitement for the historical aspect of this research: “I spent some time this past summer tracking down all of these old sites using the literature, as well as old lab notebooks here at the University of Illinois. This winter, I am excited to begin testing this archived plant material here at the lab for these natural insecticides to compare with plant material collected this past summer. Documenting changes in plant chemistry over time will be very interesting!” 

Potential Outcomes 

The wild parsnip - parsnip worm system is a useful model for understanding biological control and how closely linked plant and herbivorous insect relationships will respond to climate change. 

Jones explains, “One thing about these coevolutionary relationships is that they don't occur across the landscape in exactly the same way. Populations and their interactions can vary. For instance, compound levels produced by the plants can vary. How does this affect biological control? Understanding these systems, especially how these interactions differ at the population level, can open up new ways for using biological control, instead of a one-size-fits-all approach that assumes all populations are the same.”