Yale University researchers say salamanders breeding in roadside ponds are exposed to a number of toxic contaminants from road runoff, mainly sodium chloride from road salt.
The sodium chloride can reach concentrations of 70 times higher in roadside ponds compared with woodland ponds located several hundred feet from the road, they said.
"While the evolutionary consequences of roads are largely unknown, we know they are strong agents of natural selection and set the stage for fast evolution," Steven Brady, a doctoral student at the Yale School of Forestry & Environmental Studies, said.
"These animals are growing up in harsh environments where they face a cocktail of contaminants, and it appears that they are evolving to cope with them," he said in a Yale release Wednesday.
While salamanders in roadside ponds have higher mortality, grow at a slower rate and are more than likely to develop deformed spines and other disfigurements, surviving salamanders may develop a genetic advantage over their counterparts living in woodland ponds, he said.
Salamanders that survive year after year in roadside ponds appear to be adapting to the harsh conditions, he said.
"The animals that come from roadside ponds actually do better -- substantially better -- than the ones that originate from woodland ponds when they're raised together," Brady said.
Brady observed the development of the salamanders in 10 ponds -- five roadside and five woodland -- in northeastern Connecticut.
2014: The Year in Music [PHOTOS]