Great Smoky Mountains National Park is known for being salamander capital of the world. There are 30 different species comprised into five families which reside within the park. It’s not just their diversity in species that makes the Smokies such a salamander hot spot, but also their sheer combined biomass. If you weighed the combined biomass of all vertebrates within the park, salamanders would be the heaviest by far. Finding these abundant amphibians is as easy as turning over a few logs or stones. During nocturnal hours the forest floor seems to be littered with salamanders. Great Smoky Mountains National Park encompasses over 800 square miles of the Appalachian Mountains, and over 17,000 species have been documented within the park. Scientists estimate that additional 30,000 – 80,000 species have yet to be documented living in the park boundries. How did this temperate rainforest become such a hotbed for biodiversity? The Appalachian Mountains, glaciers, and weather over deep time have played a vital role.
About 11,000 years ago during the Pleistocene Epoch, much of North America was covered by ice. Species that were able to migrate moved south, and many found refuge within the Southern Appalachian Mountains. This resulted in many of these species to survive the ice age and diversify in the region we now call Great Smoky Mountains National Park. The Southern Appalachians were and still are the ideal habitat for salamanders. Cool, wet environments with heavy rainfall made life and reproduction possible for a wide variety of salamanders that migrated south. This environment was also ideal the salamanders food sources, which is mostly consists of small invertebrates.
During the summer of 2015, I spent extensive time in the field searching for various species of salamanders throughout Great Smoky Mountains National Park. Outside of my personal work of documenting various species within the park, I spent a few nights working with evolutionary biologist Austin Patton who is working on his PhD dissertation on examining hybridization between Plethodon jordani (Red-cheeked Salamander),Plethodon metcalfi (Grey-cheeked Salamander), and Plethodon teyahalee(Southern Appalachian Salamander). Historically, hybridization tends to be viewed as a negative force in biology. Recent literature has poised that hybridization may actually accelerate the diversification process. This could possibly result in new species better adapted to a rapidly changing environment. Patton is using modern genomic approaches to help describe the contribution of hybridization to the historical diversification of these Plethodontid salamanders and to identify its role in contemporary adaptation.
Working with Patton meant collecting P. jordani, P. metcalfi, and P. teyahalee from 9PM until 4AM in various parts of the National Park. We would take small tail clippings which will be used to examine and compare DNA amongst individuals to see which are hybridizing and where. Since salamanders have the ability to regrow their tails, these small clippings are harmless to the individual. Each salamander was released after this process. I found the geographic distribution of these three species to be quite fascinating. At one location we would only find P. joradni, and another only P. metcalfi, and so on. Where ranges overlapped, we began seeing hybrids with strange coloration and patterns that were strong signals the different species were interbreeding in these regions. Further genetic analysis will reveal the parental species and genetic make-up of the specimens collected at each site.
Worldwide declines in population numbers are nothing new to amphibians. The need for understanding species behaviors, and habitats will help lead to better protection and conservation efforts. Amphibians are very susceptible to minute changes in their environments. One study looked at historical and current pesticides that have shown up within Great Smoky Mountains National Park and their effects on salamanders. Results revealed measurable levels of many pesticides including DDT, heptachlor, endosulfan, and atrazine, some of which haven’t been used in many years. Some of these pesticides can induce developmental abnormalities, behavior alterations, and damage nervous system functioning amongst larval and adult salamanders. While the levels of these pesticides are likely too low to result in any significant deleterious effects in salamanders within the park, it’s important to know their presence.
To connect Patton’s research with the study on pesticides within the park we can for one at least understand the geographical distribution of these salamanders and where they’re hybridizing, and if these are areas high in pollutants. In addition, is it possible that hybridization could lead to individuals better adapted to cope with increased pesticide exposure in aquatic as well as terrestrial environments? These are the type of questions that can only be answered through further research on salamanders within Great Smoky Mountains National Park.
All images with a white background were shot using the Meet Your Neighbours (http://meetyourneighbours.net) technique. All salamanders were shot on location in the field and released immediately after photographing. My reason for photographing using this method is that these are nocturnal animals, and photographing them at night using flash would make their environment look unnatural. Photographing the salamanders against a white background highlights the beauty of these organisms as well as their unique coloration and detail. Click through the photographs below to see the salamanders of interest to the study as well as hybrids we found. The rest of the collection are other salamanders I found within the park.
- Erin J. Hyde and Theodore R. Simons. Sampling Plethodontid Salamanders: Sources of Variability. The Journal of Wildlife Management. vol. 65, No. 4 (Oct., 2001), pp. 624-632