Newswise – CHICAGO – On a sunny day in 2018, two DePaul bioscience faculty members spent hours picking clover in the parkways and fields of Chicagoland. Humans have spread white clover — the same species that sometimes gives lucky four-leaf clover — into ecosystems around the planet. This has made it the perfect plant to study for researchers who want to take a holistic look at how humans cause plants to evolve.
Jalene LaMontagne, associate professor of ecology, and Windsor Aguirre, associate professor of evolutionary biology, are among hundreds of researchers who have harvested clover in 160 cities around the world. The research, published this week in the journal ‘Science’, offers insight into how urbanization is changing the genetic properties of the plants and animals around us.
In this Q&A session, LaMontagne and Aguirre explain how clovers harvested from a 50-mile stretch near Chicago help illustrate the global human impact on nature.
Tell us about this research. What changes were you looking for in clover in the city versus in the countryside?
Windsor Aguire: It was a massive effort, led by researchers at the University of Toronto at Mississauga, to look around the world to see how rural environmental conditions can affect a particular species. The advantage of this species, white clover, is that it is present everywhere.
In this study, we measured the production of hydrogen cyanide, which clover produces as a defense against herbivores. The scientists wanted to know if there was a common pattern of change in the production of this compound when moving from an urban to a rural environment. And the answer is yes. Research shows that natural selection and adaptation alter the genetic structure of this species in urban versus rural habitats.
Jalene LaMontagne: We designed the sampling and walked a 50 mile (80 km) transect, starting in a densely populated area west of the loop, to where agricultural fields and horses were. We finished the transect fairly close to the Illinois-Wisconsin border.
The results indicate that clover closer to urban areas, including Chicago, lost the ability to produce the toxin hydrogen cyanide, likely because urban areas have fewer herbivores. In the paper, the researchers explore the idea of convergent evolution: populations in vastly different areas evolve to have the same traits and characteristics. This is a selection that took place over a very long period and the pattern is quite consistent.
How is this research groundbreaking and what does it signal about man’s impact on nature?
Aguire: It’s one of the largest studies of its kind, looking at a global landscape and showing a commonality of how things are changing. I’m doing research in Ecuador, and there was clover collected there also from other cities in South America, Asia, Africa, and Europe for this study.
The mountain : Global change biology is an emerging field, and it includes climate change research as well as topics like this. Urbanization is increasing at an unprecedented rate and creating selection pressures by changing the environment. White clover does very well in many different environments, but we still see changes in its properties in urban areas. We also need to think about the changes that occur in species that are much more restricted to certain environmental conditions. When this type of selection occurs, species will not be able to cope with changes in their environment. There are definitely winners and losers.
Aguire: I’m an evolutionary biologist, and our students are interested not only in climate change, but also in the broader ways in which humans are altering the planet. If organisms alter their genetic properties to respond to humans, we can examine how to preserve them and their ability to persist among predators or parasites.
It can be easy to lose the sense of the fundamental reality that we are organic beings. We depend on the planet for natural resources, and there is a real threat to the long-term viability of the planet.
What will happen next with this research? How do you plan to introduce it in class?
Aguire: There was a great advantage in using a common species. I teach classes with labs and I would like the students to sequence the genes and look for the variants of this local species.
We often think of biologists who go to very exotic places to do research. And while Jalene and I like to travel to do research, it’s nice to show some really cool examples of everyday organism evolution adapting around us.