Urbanization driving plants’ evolution 

18 Mar 2022
Mount Allison biologist part of international team studying evolution of white clover in urban areas 

SACKVILLE, NB — When many of us see the common weedy plant White Clover, we might think of lawn maintenance, honey production, or perhaps the luck of the Irish. But a group of scientists from around the globe, including a researcher from Mount Allison University, have recently published a study on the evolution of this mighty plant in urban settings.

Dr. Emily Austen, Assistant Professor of Biology at Mount Allison University, was one of nearly 300 researchers globally to contribute to the project — likely the largest ever collaborative effort in evolutionary biology. The article, Global urbanization drives adaptation in the plant white clover, was recently published in the peer-reviewed journal, Science.
“White clover has a built-in defence mechanism, it produces hydrogen cyanide, which enables it to protect itself against little herbivores like caterpillars or other insects,” explains Austen. “But there’s a trade-off for the plant to put this mechanism to use, it takes a lot of energy and resources. We collected clover samples from cities around the world to see if those in urban areas reacted differently from plants in the rural areas surrounding cities.”
The international, multi-year study examined the way that life in a city setting can impose natural selection on the non-human organisms in these areas. Specifically, the international team, known as GLUE (Global Urban Evolution), were studying how the biochemistry of White Clover changes depending on whether it is found in a city or a surrounding rural area.
Austen collected hundreds of White Clover samples in the Moncton area in the summer of 2018. She then collaborated with SHAD Mount Allison — a national STEM-focused program for Grade 10 and 11 students, hosted at university campuses across Canada — to help analyze the samples.
The study found that, in many cities, clover plants collected from the city centre were less likely to produce hydrogen cyanide than plants from rural areas around the same city, which Austen says could be attributed in part to urban-rural differences in vegetation.  “In cities, there is usually less vegetative cover, making city plants less likely to encounter herbivores.  That means that in cities, the costs of hydrogen cyanide production might outweigh the benefits.” Austen, with the SHAD Mount Allison students, tested hundreds of samples from Moncton for the study. Although they found that some plants could produce hydrogen cyanide, the probability of producing hydrogen cyanide wasn’t affected by a plant’s proximity downtown Moncton. Austen suggests that could be because Moncton is a smaller city than many of the others in the study.
“Across all of the plants from all the cities studied, there appears to be a global signature of certain biochemistry profiles being more likely to occur in cities than outside of cities,” she says. “By studying a small, weedy plant in a big, global experiment, we get an idea of adaptation to city life, and how non-human organisms evolve when we alter their environment. I’m honoured to be a part of the project and so pleased we were also able to work with the SHAD Mount Allison students who assisted greatly with the lab work and analysis for our local contribution.”
And Austen says she did appear to have a little luck on her side while collecting samples along the Petitcodiac River in 2018. 
“I found one four leaf clover, out of hundreds of clover plants collected.”


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