What can interbreeding butterflies tell us about climate change? More than you might think!

IonE Director Jessica Hellmann, with researchers from the University of Notre Dame, North Carolina State University, and Michigan State University, recently co-authored a new study published in the Proceedings of the National Academy of Sciences. The study examines movement of the Eastern (Papilio glaucus) and Canadian (Papilio Canadensis) tiger swallowtail butterfly over a 32-year period within the geographic region where the two species mate, called the hybrid zone. The researchers were able to show that the hybrid zone is moving – and these findings highlight the impact of a changing climate and provide critical information for the protection and management of biodiversity.

“Comparing specimens from the past with today gives us a way to monitor how a changing climate is reshaping biodiversity,” says Hellmann. “We need this kind of information about how species are responding in order to design effective ways of being good stewards of biodiversity – as best we can – as the climate changes.”

To learn more about the study, Hellmann pointed us to lead author Sean F. Ryan. (Hellmann served as advisor for Ryan’s dissertation at the University of Notre Dame.) Ryan, who is now a Citizen Science Fellow at North Carolina State University, kindly obliged.

Could you speak to what is unique about this study?

It is rare to have the ability to make predictions about what has happened historically and actually be able to rewind the tape and look at whether our predictions were correct. Mark Scriber [of Michigan State University] spent about 40 years of collecting these butterflies, which allowed us to do just that. More specifically, we used data taken from butterflies raised in the lab to simulate — or model — how they should be responding to historical changes in climate and then compared those predictions to empirical data (including museum collections.) Using models to make predictions and then testing those predictions with real data is often rare, but can be very powerful.  

What led you to study the patterns of butterflies specifically?

I am an entomologist by training, so I tend to focus on insects. But in this case in particular, it was really having the historical collections that sparked an interest to leverage this resource to see how climate may be affecting these species. There was also good reason to think these butterflies, or the hybrid zone more specifically, might be sensitive to changes in climate based on Mark Scriber’s work.

What do you see as the most crucial aspect of the study findings?

That’s a tough one. Personally, I think it’s the more conceptual part of the paper, where we explore how geographic variation in climatic warming, in this case in the eastern United States, might result in very different evolutionary outcomes for the populations distributed across this landscape. We present some hypotheses as to how this variation might be important, but we really don’t know. My hope is that it sparks further discussion on the topic.

How does this work fit into your bigger-picture motivations as a scientist?

I am generally interested in understanding how human disturbances — for example, climate change or the spread of invasive species — affect the ecology and evolution of insects, so this project perfectly aligned with my main research interest. This was also my dissertation research, so it was a great opportunity for me to develop skill sets — genomics and modeling — that have been valuable to my future research endeavors.  

How do you believe this study will affect or inform you and/or your work moving forward?

One of the biggest impacts it had on me was to increase my appreciation for historical collections. However, it also made me realize that we are not doing a good job collecting the data (specimens) we need to take advantage of this natural experiment that is unfolding–climate change. As a result, I started a citizen science project – The Pieris Project – that enlists the help of people from all over the world to create a long-term collection of the small cabbage white butterfly that we can use to address all sorts of questions related to how this butterfly responds to changes in its environment.  

Grace Becker is the communications assistant at the Institute on the Environment and an undergraduate student at the University of Minnesota, where she studies strategic communication, Spanish, and sustainability studies.