An international study involving Montreal researchers shows that white clover has adapted to cities

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Omnipresent in our parks and lawns, the cosmopolitan white clover has adapted to the urban environment by producing less of a substance that normally protects it from herbivorous predators, finds new international study involving Montreal researchers.

White clover typically protects itself from herbivores by producing hydrocyanic acid, a substance that gives it a very bitter taste and life-threatening toxicity, researchers said in a press release.

However, researchers from the Global Urban Evolution Project (GLUE), an international initiative involving Professors Pedro Peres-Neto and Carly Ziter of Concordia University, have found that white clover growing in cities is less likely to produce cyanide d hydrogen to defend itself than the white clover growing in the countryside.

“This is a very important change for clover because it has to do with protection against (herbivores),” summarized Professor Peres-Neto, a quantitative ecologist.

The researchers collected more than 100,000 white clovers from 160 cities on all continents. Plants were collected along a geographic gradient from heavily urban to non-urban areas. Their ability to produce hydrocyanic acid was then analyzed.

In about half of the cities sampled, scientists found that more plants produced less hydrogen cyanide in the city than in the countryside.

The plants, however, remain genetically very similar, suggesting “there is strong evolution by selection leading to reduced cyanogenesis in urban systems,” they explained.

“This species (white clover) has been introduced across the planet, so we can use a well-distributed species to generate clear and strong evidence that urban environments can alter the evolutionary trajectory of species,” Peres-Neto said.

Similar results had already been obtained at the local scale, in two or three cities, he added, “but the result fits very well on a global scale… You could say that the results have validated globally.

This adaptation of the cosmopolitan white clover provides insight into the impact of urbanization on ecosystems and their biodiversity, at a time when the United Nations predicts that two-thirds of the world’s population will live in cities by the end of the century.

Cities are totally different ecosystems from what we find in nature, Peres-Neto pointed out, “and we have to start understanding how organisms adapt to this environment because it is an environment that will develop “.

“For the management and conservation of biodiversity, which will increasingly be found in cities, it is important for us to understand what are the processes that lead to an evolution which, potentially, is different in the city compared to the environments that are outside. cities,” he explained.

Other species will adapt in other ways, he continued, “but there are not endless ways to adapt.”

While white clover has adapted by reducing its cyanide production, other plants may adapt differently to more positive (fewer predators) or more negative (more concrete, so less soil to root) conditions in cities. .

While many researchers have studied animal adaptations to cities, this study is one of the first – if not the first – to look at plant adaptations to urban environments.

But a study on this global scale would be essentially impossible to do with animals, Peres-Neto said.

“Plants make our lives easier because they don’t move,” he said.

The researchers will now try to determine if the energy that the clover once spent on producing hydrocyanic acid is now used for other purposes, such as increased reproduction or longer longevity.

The first article of the project is published in the prestigious journal Science. Professor Peres-Neto is one of the 11 main authors of the article.

— This report from The Canadian Press was first published in French on April 20, 2022.

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