Urbanization: white clover adapts to cities

Human beings have long since stopped adapting to their environment: they modify it according to their needs. The consequences are urbanized societies: globally, more people live in cities than in the countryside. However, the ever-growing urban environment also does something for the plants and animals that inhabit it.

A research team led by graduate student James Santangelo of the University of Toronto-Missisauga has now conducted a comprehensive study of how white clover is doing in cities around the world. White clover because the plant is widespread on almost all continents and is a frequent guest in urban regions. The researchers are currently presenting the results of their investigation in the journal Science.

Less hydrogen cyanide in clover

It all started with an examination of white clover in Toronto, Santangelo tells science.ORF.at. Researchers have already been able to determine that the plant produces fewer antibodies against predators in the urban environment than in rural areas. Specifically, the team found that Toronto clover produced less hydrogen cyanide, also known as toxic prussic acid.

“We had data from one city, but we wanted to broaden our survey,” says Santangelo. One city soon became two, then five. According to the doctoral student, he did not expect that the team would eventually receive data from 160 cities.

Search for experts on social media

The huge amount of data is due, among other things, to a message on a social media platform. “One of the project supervisors presented it on Twitter in several languages ​​and also asked the helpers to support us with additional data from their respective regions.” Interest in the tweet significantly exceeded original expectations: “Our goal of We had already passed 50 cities after a week or two.”

Marc Johnson

Overall, Santangelo and his team were able to access information from more than 110,000 white clover plants. “Of course, all of this was only possible because more than 280 people provided us with the data.” The volunteers – some biologists but also students – came from 26 countries: from Canada to Germany to Japan.

predators and lack of water

Using the data, the team was able to show that the amount of hydrocyanic acid in plants in about half of all cities surveyed differs significantly from rural white clover. In addition, the researchers also sequenced some 2,500 genomes of clover samples from cities and rural areas to be able to determine changes in plants even more precisely. A database has been created which, according to Santangelo, also forms a good basis for numerous other field investigations.

Where the amount of hydrocyanic acid in rural plant clover differed, the team found commonalities between different cities. “It is almost always true that plants in urban environments produce less hydrogen cyanide,” says Santangelo. Researchers cite fewer predators such as insects and stressors such as low water for plants as the two main reasons for this. Rob Ness, leader of the research project, explains: ‘The result of the study is the strongest evidence that we humans significantly influence the evolution of life of all types in the habitats we create.’

Cities look alike all over the world

According to Santangelo, the result of the study also clearly shows one thing: “Regardless of whether it is Tokyo, Toronto, Melbourne or Munich, urban living spaces are much more similar to each other than, for example, Toronto and the surrounding areas. more rural “. The ecosystem of large cities is therefore comparable in some respects, regardless of where you are at the moment.

In addition to providing the basis for further investigations into the evolution of urban habitats, Santangelo sees the importance of the study in nature conservation, among other things: “White clover is one of the most important sources of pollen for bees or other pollinators. in urban regions. If we understand better how the ecosystem of cities affects plants, it can also help us protect them, “says Santangelo.

Furthermore, the research group’s findings can also be used to better protect the urban ecosystem and the people who inhabit it. “The mechanisms that drive evolution are almost always the same, regardless of species,” says the graduate student. According to him, research into how clover fits into cities could also allow conclusions to be drawn about plant and animal species that could be invasive or disease-carrying if they spread to cities.

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