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Urbanization is driving evolution of plants globally, study supported by Laurentian U finds

Second year Biochemistry student, Danica Levesque, amongst researchers published in the journal, Science.

(March 21, 2022) - Humans re-shape the environments where they live, with cities being among the most profoundly transformed environments on Earth. New research now shows that these urban environments are altering the way life evolves.

A ground-breaking study led by evolutionary biologists at U of T Mississauga (UTM) examines whether parallel evolution is occurring in cities all over the world. In findings published in the journal Science, the Global Urban Evolution Project (GLUE) analyzed data collected by 287 scientists in 160 cities in 26 countries, who sampled the white clover plant in their cities and nearby rural areas. Included samples derived from Greater Sudbury; fieldwork and data analysis supported by Laurentian University Biochemistry professor, Dr. Thomas Merritt, Lila Elizabeth Merritt, and second year Biochemistry student, Danica Levesque. 

The study has found the clearest evidence yet that humans in general, and cities specifically, are a dominant force driving the evolution of life globally. Discovered is that white clover is frequently evolving across the globe and in direct response to environmental changes taking place in urban settings. 

The GLUE study illustrates that the environmental conditions in cities tend to be more similar to each other than to nearby rural habitats. In that sense, downtown Sudbury is more comparable to downtown Tokyo in many ways than it is to surrounding farmland and forests outside of the city. Nevertheless and explained by Dr. Merritt, “similar to genetics, evolution is complicated. Patterns vary, but the more examples that we have of studies rooted in our real world, the easier it is to explain and understand the complexities of genetics and evolution.” 

Not only were researchers able to observe global adaptation to cities, they identified the genetic basis of that adaptation and the environmental drivers of evolution. White clover produces hydrogen cyanide as both a defense mechanism against herbivores and to increase its tolerance to water stress, and GLUE found that clover growing in cities typically produce less of it than clover in neighbouring rural areas due to repeated adaptation to urban environments. 

It is the changes in the presence of herbivores and water stress in cities that is pushing white clover to adapt differently than their rural counterparts. That finding holds true for cities across various climates, and the implications reach far beyond the humble clover plant.

Speaking about the inclusion of Greater Sudbury in GLUE, Dr. Merritt said that “one of the real strengths of Laurentian is that geographically, we are close to an edge. For many species, you don’t get a whole lot North of where we are. So, while this is something that we often think about as being a bit of a challenge, scientifically, our location is a real asset and we are able to be a part of these studies because we really are at the Northern edge of many things.” 

Impressively, Levesque was but sixteen years old and in grade 11 at École Secondaire Sacré-Coeur, when she got involved in GLUE. As a high school student, she advocated for her interest in the field of Biochemistry when she reached out to Laurentian to inquire about a research internship. “Having Danica on board has been incredible,” said Dr. Merritt. “One of the best parts of being a professor is watching a student generate their first data set. It’s the kind of thing that sticks with you.” Danica will be working in the lab this summer on an N-SERC USRA fellowship

“My participation in GLUE has been awesome. This experience was my first time ever in a lab. I was just very thrilled to be involved, get my hands dirty, see results, and contribute to this study,” said Levesque who is also on Laurentian’s Varsity Women’s Nordic ski team. “To be a part of a project of this magnitude has been amazing.” 

The project is a model for inclusive science. The team was equally split between women and men and included not just established researchers, but also students at all levels and from all inhabited continents across the world. This publication is just the beginning for GLUE that supports an unprecedented global collaboration.