St. Olaf Magazine | Fall 2018

Monarchs, milkweed, and migration

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Each year, millions of monarch butterflies migrate from northern Minnesota to Mexico — and along the way, they rely on milkweed for their food source.

Some evidence suggests that most monarchs overwintering in Mexico have fed on the same milkweed species that is common in Minnesota. This summer, St. Olaf College researchers are looking at whether there is local adaptation in milkweed across the vast monarch migration route.

Bethany Tritz ’20 and Diane Vargas ’19 are working with St. Olaf Assistant Professor of Biology and Education Emily Mohl to determine patterns of local adaptation of common milkweed, Asclepias syriaca, from different locations.

An example of milkweed that DeeDee Vargas ’19 and Bethany Tritz ’20 are growing in the campus greenhouse.

“People are planting lots of milkweed right now to support monarch butterflies,” Mohl says. “With all of these efforts, it would be really useful to know how important it is to use local varieties of milkweed.”

The St. Olaf team’s work will help inform national conservation efforts like the Monarch Highway, which aims to develop a stretch of milkweed along the I-35 highway from Minnesota to Texas to support monarch butterflies on their migration. Milkweed is a crucial food source for monarchs, which are declining in population.

“People are concerned whether or not the milkweed that is going to be planted is locally adapted — so the same milkweed that comes from northern Minnesota might not be the same from southern Minnesota, and then you’re planting it all over the country and what happens then? So our study is mainly focused on how local adaptation will affect these milkweed,” Tritz says.

In addition to studying the adaptability of milkweed, the St. Olaf researchers are also creating curriculum to better inform students of all ages about plant adaptation and to involve them in data collection to help answer novel questions.

The team’s work is part of the college’s Collaborative Undergraduate Research and Inquiry (CURI) program, which provides opportunities for St. Olaf students from all academic disciplines to gain an in-depth understanding of a particular subject by working closely with a St. Olaf faculty member in a research framework.

“I’m interested in doing something in the ecology field or something with conservation biology in graduate school, so I felt like working in the field with plants like milkweed that need to be conserved would be a great way to gain that experience and knowledge,” Vargas says.

As a biology major, Vargas will be studying different traits in milkweed, including the phenology — when the flowers and seed pods will come out — the number of flowers and pods on each plant, what chemicals are in the plants that protect them from herbivores, and what pollinators will be on the plants. She will then see if any of these traits are consistent with patterns of local adaptation.

“I am testing the effects of biotic factors on different milkweed plants from different geographic locations, and I’m doing this by having two different plots of milkweed plants in which there are three different types of milkweed from different locations,” Vargas says.

DeeDee Vargas ’19 tagging a campus milkweed plant for easy identification and future observation.

On the other side of the research, Tritz, a biology and science education major, is putting together an authentic science curriculum for middle school to college students on milkweed, including local adaptation, evolution, and the monarch life cycle. Her work will allow more teachers to access and use the curriculum.

“Authentic science curriculum is where real data and real research are being used in the classroom to teach science,” Tritz says. “This is different from a normal curriculum, because we want students to know science isn’t just the facts— it’s research, it’s asking questions, it’s ‘how does this thing work’ and not just ‘this is how this works.’ The curriculum is presenting all of these studies and all of this data and asking students to try to interpret it. That’s what research is.”

Bethany Tritz ’20 measures a milkweed plant growing near Regents Hall of Natural and Mathematical Sciences.

She will also be assessing the effectiveness of authentic science by comparing essays and surveys written and taken by students from before and after they were taught with this technique.

“Bethany and DeeDee are building on work that students have been producing for years now, and we’re starting to get to a place where we can make informed hypotheses about what might happen if we move milkweeds from one place to another,” Mohl says.

For Mohl, these years of study and conversation with students have been integral to her own work as a researcher.

Researchers (from left) DeeDee Vargas ’19, Professor Emily Mohl, and Bethany Tritz ’20 discuss growth and changes in their milkweed plants.

“Being a part of a research lab is really valuable,” she says. “You can’t really do research effectively by yourself, so having students who are willing to spend dedicated time and energy thinking about the projects you want to be working on is a great opportunity.”