A Pseudotriton ruber, one of 15 salamander species found in the Appalachian mountains. The word "salamander" means fire lizard when translated from its Greek origin.
Salamanders of Appalachia
By Jennifer Amie
July 17, 2007
In the southern Appalachian mountains, more than 60 species of Plethodontid salamanders make their homes in swift-running streams, under cool rocks, and along the damp forest floor. (Appalachia stretches from southern New York to northern Alabama, Mississippi, and Georgia.)
For the past 10 to 15 million years, salamanders have inhabited this mountain environment, which is well suited to lungless amphibians that require cool, moist conditions to "breathe" through their skin.
As many as 15 salamander species can be found living side by side in these mountains, each inhabiting a specific ecological niche. The Appalachian forests are so moist that some species can live their whole lives out of water. At the same time, giant predatory salamanders prowl the streams and have the longest aquatic larval period on earth, lasting up to four years. The tremendous diversity and density of salamanders in this region is the research focus of herpetologist Kenneth Kozak, who has joined the University of Minnesota's Bell Museum of Natural History as curator of reptiles and amphibians.
"A lot of salamander species appear to be originating in these mountains," says Kozak, who is also an assistant professor in the Department of Fisheries, Wildlife, and Conservation Biology on the Twin Cities campus. "And we want to know what it is about this environment that enables so many species to accumulate there." Using information from museum collections, DNA analysis, and sophisticated climate data, "we're getting closer to understanding how species interact with their environment in space and time to increase species diversity," he says.
Today's advanced geographical information systems (GIS) provide a wealth of environmental data useful to biologists. For example, if a particular salamander species is known to inhabit a certain mountaintop in southern Appalachia, Kozak can use GIS data--gathered by weather stations, remote sensing, and other means--to identify locations that share the same, or similar, environmental conditions. A neighboring mountaintop identified that way may also harbor the salamander or one of its close relatives. In addition to helping scientists determine where species live, and under what conditions, the data can shed light on a number of interesting questions, such as how species have adapted to changing environments over time.
University of Minnesota herpetologist Kenneth Kozak.
"With GIS maps, you can instantly obtain information on temperature, precipitation, and seasonality," says Kozak. "This is a new, sophisticated technique that we didn't have before. For the first time, we are able to obtain detailed predictions on the geographic locations of suitable habitats now, in the past, and in the future."
Sisters in sheddingOne fascinating phenomenon is the discovery of salamander "sister species" that inhabit different mountaintops widely separated by inhospitable (warmer and drier) valleys. Sister species are two species that are each other's closest relatives--in other words, they most recently shared a common ancestor. Kozak is particularly interested in how new species originate, a fundamental question in evolutionary biology since Darwin.
"We know that populations need to get isolated and separated to become new species," he says, "but we lack information as to how they became isolated in the first place." In this case, climate models indicate that the valley was once cooler and wetter--a habitat that was able to support the ancestor shared by the sister salamander species. "As the climate becomes warmer and drier over time, salamander species can either go extinct, adapt to drier conditions in the valleys, or track the cool, moist conditions as they recede up the side of the mountain," says Kozak.
What Kozak has found is that the salamanders were unable to adapt to the drier, warmer valleys that emerged in a hotter climate. Instead, the changing environmental conditions pushed the salamanders further up the mountainsides in search of suitable habitat, eventually isolating two populations on separate mountaintops. The population, which can no longer interbreed, evolve into separate species as each adapts to slightly different environmental conditions in different locations, and through random loss of genetic traits.
The fact that these salamander species were unable to adapt to a drier, warmer climate raises concerns for the amphibians' survival in an era of rapid global climate change.
"In the past, the climate changed less rapidly and oscillated between warmer and cooler periods," says Kozak. "What will happen as the climate changes more rapidly and more drastically, and if it does not cool down again? The salamanders may have nowhere to go."