Research reveals how humans are changing the way life evolves

By Mark Waghorn via SWNS

Humans are changing the way life evolves as plants and animals adapt in unusual ways because of us, according to new research.

The phenomenon - dubbed "unnatural selection" - is one of the greatest biological forces on Earth.

It has created "parallel urban worlds" where wildlife has had to respond - or die.

Co-lead author James Santangelo, a PhD student at the University of Toronto, explained: "We have long known we have changed cities in pretty profound ways.

"We have dramatically altered the environment and ecosystems.

"But we just showed this happens, often in similar ways, on a global scale."

The finding is based on an analysis of white clover collected from 160 cities and nearby rural areas in 26 countries.

A familiar weed of British gardens, it is famous for its three trefoil leaves.

It provides the clearest evidence to date that people in towns and cities are driving nature.

The shamrock plant is genetically altering from London to Lisbon, Toronto to Tokyo and Melbourne to Munich.

Humans are profoundly transforming their surroundings - which is dramatically impacting organisms they share them with.

The Global Urban Evolution Project (GLUE) study showed conditions tend to be more like each other than nearby rural habitats.

So downtown Toronto is more comparable to downtown Tokyo than to farmland and forests just outside the city.

For instance, white clover produces hydrogen cyanide to deter herbivores and increase tolerance to drought.

The international team found city varieties produce less due to changes in the presence of plant eaters and water stress.

It applies across different climates - and the implications reach far beyond the humble clover.

Co-lead author Dr. Rob Ness, also from Toronto, said: "This study is a model to understand how humans change the evolution of life around us.

"Cities are where people live, and this is the most compelling evidence we have that we are altering the evolution of life in them.

"Beyond ecologists and evolutionary biologists, this is going to be important for society."

White clover is present in almost every city - providing the perfect tool to investigate human influence on evolution.

It began with the domestication of dogs 30,000 years ago. Now industrialized farming, introduced species, urbanization, pollution and climate change are creating unprecedented selective pressures.

Evolution - at least for larger, more complex organisms - can be slow. It leaves many animals unable to adapt fast enough.

But rapid change is also possible, via an inbuilt genomic plasticity. The most famous example is the peppered moth.

It changed from speckled white to black in response to soot and air pollution rising from the chimneys of the Industrial Revolution in Britain.

Today, worker bees in industrial beehives - transported from farm to farm across the United States in convoys of trucks - are one-third larger than their wild cousins, and more docile.

In the past 100 years, North American songbirds have modified the shape of their wings to cope with habitats fragmented by deforestation.

Under pressure from poaching, Zambian elephants are born without tusks.

Since the introduction of cane toads to Australia in 1935 to deal with beetle infestations in sugar plantations, the mouths of black snakes have shrunk.

Succeeding generations learned to avoid toad-sized prey, while the toads themselves have become cannibals, victims of their own success as predators.

Sea-snakes in Papua New Guinea have developed darker bodies and shed their skins more often in response to toxins in the zinc-polluted waters they inhabit.

One species of mosquito has evolved to live only in the tunnels of the London Underground, and lost the capacity to breed with its surface-dwelling cousins.

Similar declines in genetic diversity have been observed in mosquitoes in the New York and Chicago subway systems.

Blackcaps have shifted their migration routes from the Iberian Peninsula to the UK as climate change extends their range.

Swans that avoid cities have a genetic difference from the ones that are human-tolerant.

The study in the journal Science opens the door to developing strategies to conserve rare species in towns and cities.

It can also help us better understand how to prevent unwanted pests and diseases.

The 287 scientists have sequenced more than 2,500 clover genomes from over 110,000 samples.

They have created a massive dataset that will be studied for years to come. The unprecedented initiative began with a single Tweet.

Added co-lead author Prof Marc Johnson, also from Toronto: "Nearly everyone we asked to collaborate said yes - and that was kind of remarkable, because we were asking people to take on a lot of work,.

"Our collaborators recognized the importance of this project. There has never been a field study of evolution of this scale, or a global study of how urbanization influences evolution.

"It would have been impossible to do this without our global set of collaborators."