The speed at which a tiny ant evolves to cope to its warming city environment suggests that some species may evolve quickly enough to survive, or even thrive, in the warmer temperatures found within cities, according to a new study by researchers at Case Western Reserve University.
It has been found that the urban acorn ants collected in Cleveland have taken no more than 100 years to adjust to their heat-trapping home of asphalt and concrete steeped with waste heat from cars and buildings.
“Ants are an indicator species, and by comparing the physiologies of urban versus rural ants, we can get an idea of whether ants and other cold-blooded animals will be able to cope with the temperature changes associated with urbanization and other sources of warming like global climate change,”
said Sarah Diamond, assistant professor of biology at Case Western Reserve and the study’s lead author.
Cities tend to be warmer than surrounding rural areas. To determine if the animals truly evolved or were just adjusting to the added warmth, the research team collected and compared acorn ants from the city and nearby rural land.
To isolate evolutionary change from short-term acclimation, groups of rural and city ants were raised in warmer city temperatures for about 10 weeks. Other groups from both locations were raised in cooler rural temperatures for also about 10 weeks.
Diamond believes the Cleveland ants evolved as the city became and remained highly urban during the last 100 years. Because egg-laying queen ants live from five to 15 years, the evolution to heat tolerance likely took no more than 20 generations, the researchers estimated.
With temperatures predicted to rise at least a couple of degrees Celsius over the next century, “Global data suggests that the acclimation response won’t be enough to respond to climate change, but some species, like the acorn ants, may evolve quickly enough,” Diamond said.