How Cities Reshape the Evolutionary Path of Urban Wildlife – WIRED

This urban sameness is allowing researchers to determine whether isolated populations of the same species develop similar adaptations when placed in parallel environments. What cities offer us is this amazingly large-scale, worldwide experiment in evolution, where you've got thousands of life-forms that are experiencing the same factors, says Marc Johnson, who heads an evolutionary ecology lab at the University of Toronto Mississauga.

Laypeople can be forgiven for not instinctively sharing that enthusiasm, however: At first glance, settling the decades-long debate over evolution's replicability doesn't appear likely to make our post-climate-change lives any less hellish.

But in the quest to satisfy their intellectual curiosity, urban evolution researchers are also revealing the fundamental genetic attributes that make some species adept at adjusting to urban lifeintelligence that could give us the power to forecast evolution's winners and losers in a world that's increasingly hot and crammed with people. When he concluded that killifish in four US cities had developed the same form of toxin resistance, for example, Andrew Whitehead ascribed the species' evolutionary success to its high degree of genetic diversitythat is, the killifish genome naturally contains an abundance of genetic information that isn't usually expressed. So the key to desensitizing the aryl hydrocarbon receptor was probably already present inside killifish DNA, and natural selection simply brought it to the fore.

When the environment changes very rapidly, and changes in a way that poses fitness challenges, then species that are going to be able to adaptively respond to that are ones that already have the necessary genetic diversity in hand, Whitehead says. The environment is changing right now. You can't wait for migrants. You can't wait for new mutations.

Urban evolution researchers are grappling with the question of how their work can help make the reality of a ravaged environment less grim.

Perhaps the greatest asset any creature can have hidden in its genome, of course, is the capacity to withstand heat. With global temperatures set to rise by as much as 9 degrees Fahrenheit by the turn of the century, the species likeliest to survive will be those that develop traits to guard against the broil. Today's cities, which are typically 2 to 5 degrees warmer than their surroundings, offer a sneak preview of how evolution will reshape wildlife on a sweltering planet.

The humble acorn ant is among the city-loving harbingers of the genetic churn that lies ahead. Two researchers at Case Western Reserve University, Sarah Diamond and Ryan Martin, have found that acorn ants they collected in both Cleveland and Knoxville, Tennessee, are able to thrive and reproduce in much warmer conditions than those from rural habitats. They hypothesize that natural selection may have favored urban ants whose genes manufacture more robust heat-shock proteins. If they can sort out the genetic markers linked to that suddenly useful trait, we may be able to tell which other species have the potential to adapt when the mercury rises and which are in danger of roasting into extinction.

Diamond hopes that evolutionary prediction will lead to smarter conservation choices. If we know which taxa are most vulnerable to urbanization, she says, then we can do something about it before biodiversity might be adversely impacted. That could involve simple things, such as building strategically situated green spaces within cities. In extreme cases, though, our only option for preserving some species may be to uproot and transport entire populations to distant lands.

There is an intriguing flip side to the idea that urban evolution research can be used to rescue species that lack the capacity to flourish in megacities: If we can identify which animals are genetically primed to adapt well to living amid glass and steel, we might be able to use that knowledge to engineer a more hospitable world for ourselves. That's because certain species, once tweaked in clever ways, have the potential to help heal the environment.

Take oysters, whose feeding process involves filtering harmful bacteria and contaminants out of up to 50 gallons of water per day. The gelatinous mollusks were once abundant in America's urban rivers and bays, but they were largely gobbled up by shellfish lovers decades ago. By the time anyone realized it might be environmentally wise to have massive oyster beds in places like New York, it was too late for the populations to be easily revived: Underwater landscapes had been ruined by decades of dredging and dumping, as well as saturated in anthropogenic pollutants that cause fatal oyster diseases.

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How Cities Reshape the Evolutionary Path of Urban Wildlife - WIRED