Small plant, big research: white clover is undergoing the same mutation in cities around the world

Urbanization is increasingly transforming the rural and natural environment into an ecosystem the Earth has never known, and this change is affecting the evolution of life,” concludes lead researcher James Santangelo, University of Toronto, in the scientific journal Science†

Santangelo has collaborated with an almost endless line of co-authors, who have read the genetic code of white clover in one hundred and sixty cities around the world – a “cosmopolitan plant”, in their own words. Closer to the city center, plants, also abundant in the Netherlands, were found to have less active genes for hydrocyanic acid. After all: there are fewer animals in the middle of town that eat clover, so the usefulness of these genes is limited.

It has been known since the 1950s that certain plant and animal species in the city change shape. The classic example is the birch tree, also known as the salt and pepper moth, which at the time became darker in English towns: more pepper, less salt. The birch trees on which the butterflies sat were also turning increasingly black, due to air pollution.

Urban ecology

However, the field of “urban ecology” is not the last ten years strongly emerging. the one study after another appears, showing that urban life does not leave plants and animals untouched. The yellow city jasmine, for example, produces more flowers because the pollen is harder to spread, the cardinal’s moth is less sensitive to light, the swans are less shy, and the azure damselfish can fly farther because its habitats are further away.

These are all examples of evolution in a certain city, somewhere in the world. This is what makes the study on white clover, published Thursday, so innovative: an evolution on a global scale has been demonstrated for the first time.

“I think it’s an encouraging study,” says Barbara Gravendeel, senior researcher in evolutionary ecology at Naturalis and endowed professor of plant evolution at Nijmegen, herself not involved in the paper. Science† “We usually hear that humans are ruining everything, that species are disappearing. But it shows that plant species that have been around for millions of years are finding a way to interact with humans.

Seeds up close

It is an advantage for clover that it does not have to defend itself so actively against gnawing insects in the city. Gravendeel: “Life in the city is subject to many disturbances: sometimes it is stiflingly hot, then the street is swept away again. If plants don’t need to expend energy to make antibodies, they can grow, flower and produce seeds very quickly.

According to Gravendeel, knowledge of the evolution of urban species can help humans. “Now you see that such a plant population adapts very quickly. If you are planting new plants or trees in town, it is therefore advisable to always take seeds from nearby. Young plants are more likely to survive. Ultimately, it’s also better for humans, because they won’t be living among all the dying, withered trees in a few years.