Assistant Professor of Biology Bradley Cosentino has frequently studied the eastern red-backed salamander (Plethodon cinereus), both in the lab and in its natural environment: the woodlands in the northeastern part of the United States and Canada. His recent research, as seen in an article he recently published in the journal Ecology and Evolution, explores the small amphibian’s response to global change — which may be related to a genetic color variation.
The article, titled “Evolutionary response to global change: Climate and Land Use Interact to Shape Color Polymorphism in a Woodland Salamander,” was a sweeping project reviewing research materials dating back more than a century. “This was a database study,” says Cosentino. “We looked at studies going back to the 1880s. It’s a huge dataset looking across time.”
Those studies analyzed the morph frequencies among 238,591 individual salamanders from 1,170 sites in North America. Morph frequencies, in this case, refers to a color variation found in the salamanders: some display a pronounced dorsal stripe; others do not. “Animal color in general is a trait that biologists have studied for a long time because it’s so visible,” says Cosentino. “There also tends to be other traits that go along with color.”
This is true for salamanders. Based on records over the past century, Cosentino says, the striped salamanders have been associated with cooler northern locations and higher elevations. As temperature warms due to climate change, morph frequencies are expected to shift more toward the unstriped morph, which is associated with warmer conditions. But this is complicated by variations in each region and possibly, Cosentino and his colleagues proposed, by an effect of forest fragmentation on microclimatic conditions. Forest fragmentation creates warmer conditions at the soil surface where salamanders live.
“The goal [of this study] was to put together a test of the contributions made by both regional climate and local land use on color variation in the salamanders,” says Cosentino. What they found, Cosentino and his colleagues wrote in the article, was that “ambient temperature and forest cover can interact to affect the spatial distribution of [color variation].” Striped salamanders were found most frequently in cool, northern latitudes, but they also occurred at high frequencies in southern latitudes where there was excellent forest cover. The unstriped variation, meanwhile, was primarily found in warm regions where the forests had been disturbed by urbanization and agriculture. Both temperature and forest cover, the study found, had a major impact on the salamanders.
This study shed new light on the potential for evolutionary responses of species to global change. The effects of climate warming on animal traits may be buffered to some extent by maintaining forest cover. Cosentino is planning for future research. “Now what we want to do is go back to some of these sites that were sampled in the past and look at whether the morphs have changed, and link these changes to climate and land use changes.”