Highlands, Hellbenders, and History:
Exploring the rich biodiversity of the Blue Ridge Mountains
— By Dr. Amy Boyd, Professor of Biology, Warren Wilson College
The Blue Ridge Mountains are one of the most biologically diverse areas in North America. These are very old mountains, formed at least 440 million years (compare that to the relatively young age of the Rockies, which are only 55-80 million years old). Their age makes them well weathered, with soft curves and a relatively low profile. But their age also means that life has been evolving here for a very long time, leading to a high amount of biological diversity and endemism.
The history of the mountains has helped shape and encourage that biodiversity. Plants and animals found refuge here during the Pleistocene glaciation, when ice covered much of North America but did not reach down into these mountains. During this period, organisms adapted to cold Northern climates moved south into these mountains, and some, such as the firs on our highest peaks, still remain. In addition, you can find here some species with a more tropical affinity, such as the pawpaws (Asimina triloba). Interestingly, there is a very strong connection between species found in the southern Appalachian Mountains and eastern Asia. Some plant groups, such as tulip poplars (Liriodendron) and silverbells (Halesiat), are found only in these two areas, completely missing from the rest of the planet. Why? Again, the answer lies in glacial history: the groups were widely distributed, but were wiped out by glaciation throughout the range except for the refugia in these two areas.
Another reason for the high biodiversity is the diversity of habitats. If you drive from Asheville, NC, to the top of Mt. Mitchell, the highest point in the U.S. east of the Rockies, you will drive through an equivalent spectrum of ecosystems as if you were driving from Asheville to northern Maine—and it only takes about 45 minutes. Get to the top, and you find yourself in something very similar to boreal forests, with fir trees and species only otherwise found in much more northern forests.
Our mountains have some particularly interesting and unusual ecosystems nestled among the more typical forests. One of these is the mountain bog, a wetland system whose origins are uncertain but which house rare and endangered plants such as the mountain sweet pitcher plant (Sarracenia jonesii) and the swamp pink (Helonias bullata). Another is the high-elevation rock outcrop, where thin soils and exposure restrict inhabitants to specialized plants and animals such as the Virginia big-eared bat (Corynorhinus townsendii virginianus) and spreading avens (Geum radiatum).
These forests were transformed more recently by the chestnut blight. You don’t have to look very hard in these forests to find small American chestnut shoots, even though the adults of this species were wiped out by the chestnut blight fungus in the early part of the 20th century, and the fungus still prevents existing plants from ever reaching reproductive maturity. This species was majestically dominant in these forests before the blight, and was enormously important to wildlife, generating huge quantities of nuts that fed deer, turkeys, bear, and many other forest animals. Today, shoots still emerge from underground roots that remain from some of these decimated giants.
The North Carolina mountains are home to more species of salamander than any other area of comparable size in the world, with more than 45 species from 5 different families. Some are restricted to a single small watershed or one mountain peak. More specifically, our mountains are the world center for diversity of Plethodontids, the lungless salamanders, which breathe solely through their skin. Many of them have evolved brightly colored skin patterns to warn predators of their toxicity, and some have evolved coloration that mimics one another so that they share in the benefit of this warning signal. They are often the most abundant vertebrate in the forest, with densities up to 2 per square meter, and play an important role in food webs, as both predators and prey. New species of salamander are still being discovered; for example, the patch-nosed salamander (Urspelerpes brucei) was discovered in 2009 and represents an entirely new genus. It is also the smallest salamander in the country, reaching only about 2.5 cm long at its peak of growth. On the other end of the spectrum, southern Appalachian mountain streams are home to the hellbender (Cryptobranchus allegheniensis), a salamander that can grow to an astounding total length of up to 74 cm. They are the third largest salamander in the world, surpassed only by their two Asian cousins (another Appalachian/Asian connection).
The Blue Ridge Mountains are a center for diversity of land snails, and millipedes reach record diversity levels here, with over 230 species. They are home to more than 250 birds, 78 mammals, 58 reptiles and 76 amphibians, and more tree species than all of Europe. Hike deep into the steepest gorges and you will find more old-growth forest stands than in any other Southern Appalachian state. Finding these wonders amidst the moist, dense greenery of our forests may require turning over logs to look for salamanders, getting down on your knees to appreciate the exquisite tiny mosses, or looking carefully at leaf shapes to notice the incredible diversity of tree species. But your efforts will be rewarded with a rich and diverse experience of natural history that has been evolving in this place for more than 400 million years.