IMPRINT, the Bell Museum's quarterly magazine for members, offers stories of scientific adventure and discovery, insight into today's rapid environmental changes, updates on museum programs and exhibits, and fun activities for kids. IMPRINT is published quarterly and is available as a benefit of Bell Museum membership.

Our most current cover story is below. For past articles, see the Imprint archives.

For more articles, view the Director's Column.

Salamanders of Appalachia: Evolution and Climate Change in a Biodiversity Hotspot
by Jennifer Amie

In the mountains of southern Appalachia, more than 60 species of Plethodontid salamanders make their homes in swift-running streams, under cool rocks, and along the damp forest floor. 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 Bell Museum as curator of reptiles and amphibians and who is also an assistant professor in the University’s Department of Fisheries, Wildlife, and Conservation Biology.

"A lot of salamander species appear to be originating in these mountains" says Kozak, "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, Kozak explains, “we’re getting closer to understanding how species interact with their environment in space and time to increase species diversity.”

Today's advanced geographical information (GIS) systems 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. If a neighboring mountaintop is found to share the same, or similar, environmental conditions, it 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 availability of vast and detailed environmental data sheds light on a number of interesting questions—including how species have adapted to changing environments over time. “With GIS maps,” says Kozak, “you can instantly obtain information on temperature, precipitation, and seasonality. 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.”

One 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,” says Kozak, “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." 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. This isolation leads to speciation as the two populations no longer interbreed, as each adapts to slightly different environmental conditions in different locations, and through genetic drift.

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.”