March 26, 2014
Appalachian Salamanders Appear To Be Shrinking Due To Climate Change
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Brett Smith for redOrbit.com - Your Universe Online
New research from a team of American scientists has found that salamanders living in the Appalachian Mountains have been getting smaller and smaller over the last 55 years as climate change gradually makes their habitat warmer and drier.
Published in the journal Global Change Biology, the new study was based on the examination of museum specimen salamanders collected between 1957 and 2007. The body sizes of these amphibians were compared to those of wild salamanders gathered between 2011 and 2012.
From specimens dated 1980 onward, the study team noted that salamanders were 8 percent smaller, on average, compared to the same species from earlier years.
"This is one of the largest and fastest rates of change ever recorded in any animal," said study author Karen R. Lips, an associate professor of biology at the University of Maryland. "We don't know exactly how or why it's happening, but our data show it is clearly correlated with climate change."
"We don't know if this is a genetic change or a sign that the animals are flexible enough to adjust to new conditions," Lips said. "If these animals are adjust, it gives us hope that some species are going to be able to keep up with climate change."
The new study was mostly inspired by the work of University of Maryland biology professor Richard Highton, who started collecting Appalachian salamanders in 1957. An analysis of Highton’s records showed that starting in the 1980s; the salamander population in the region – an ideal habitat for the tiny amphibians – began to decline.
Between summer 2011 and spring 2012, the researchers trapped, assessed and took DNA samples from wild salamanders at 78 of Highton's collecting sites from Maryland to North Carolina. Using recently developed solutions for investigating DNA from preserved specimens, the scientists tested a few of Highton's salamanders for disease, but the team did not find significant evidence of illness. When the researchers evaluated size measurements of the older specimens with today's wild salamanders, the contrasts were striking, they said.
Between 1957 and 2012, six salamander species became considerably smaller, while only one got slightly larger. On average, each generation was one percent smaller than its parents' generation, the scientists found.
The scientists contrasted modifications in body size to the salamanders' location and their sites' elevation, temperature range and rainfall. They discovered the salamanders shrank the most at southerly locations, where the effects of climate change appeared to be the most profound.
To determine how climate change affected the amphibians, Clemson University biologist Michael W. Sears used a computer program to generate a synthetic salamander, which permitted him to approximate a common salamander's everyday activity and the amount of calories it burned. Using comprehensive weather records, the study team was able to emulate the minute-by-minute behavior of individual salamanders, derived from weather conditions at their home locations during their lifetimes.
The model showed the modern salamanders were just as active as their ancestors had been. However, to preserve that activity, they had to use 7 to 8 percent more energy, as the metabolism of cold-blooded animals' metabolisms speed up as temperatures increase.
The researchers said salamanders must compensate for that extra energy. This means they could be spending more time foraging for food or resting in cool ponds, and less time searching for mates. The smaller amphibians may also have fewer young, and might be more vulnerable to predators.
"Right now we don't know what this means for the animals," Lips said. "If they can start breeding smaller, at a younger age, that might be the best way to adapt to this warmer, drier world. Or it may be tied in with the losses of some of these species."