Stephen G. Tilley
Myra M. Sampson Professor of Biological Sciences
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Stephen G. Tilley earned his Ph.D. from the University of Michigan.
My students and I work in a realm of evolutionary biology that is concerned with how populations undergo genetic differentiation and evolve toward becoming different species. We ask what species of animals actually are.
We work primarily with "dusky salamanders" of the genus Desmognathus, a group that is restricted to eastern North America and achieves its highest diversity in the southern Appalachian Mountains. Characters that humans can readily perceive and measure, such as behavior, color, shape and size, seem to evolve very slowly in these creatures. Different forms can thus be genetically distinct and reproductively isolated while being morphologically extremely similar. Our studies, using both starch gel electrophoresis and nucleic acid sequencing, have revealed that what were once thought to be single species of Desmognathus are, in fact complexes of forms that have undergone considerable genetic differentiation. Since 1996 our work has led to the partitioning of Desmognathus ochrophaeus into a complex of five species, including two new forms: Desmognathus orestes and Desmognathus abditus. We are currently concentrating on a complex of species and populations in the southern Appalachian Mountains of eastern Tennessee and western North Carolina. We are investigating patterns of genetic divergence and evolutionary relationships among populations and species.
Tilley, S. G., and M. J. Mahoney. 1996. "Patterns of genetic differentiation in salamanders of the Desmognathus ochrophaeus complex (Amphibia: Plethodontidae)." Herpetol. Monogr. 10: 1–42.
Mead, L. S., and S. G. Tilley. 2000. "Ethological isolation and variation in allozymes and dorsolateral pattern between parapatric forms in the Desmognathus ochrophaeus complex." Ch. 8, pp. 181–198 in The Biology of Plethodontid Salamanders, R. C. Bruce, R. G. Jaeger, and L. D. Houck, eds. Kluwer Academic, Plenum Publishers.
Tilley, S. G. 2000. "Systematics of Desmognathus imitator." Ch. 5, pp. 121–147 in The Biology of Plethodontid Salamanders, R. C. Bruce, R. G. Jaeger, and L. D. Houck, eds. Kluwer Academic, Plenum Publishers.
Tilley, S. G., and J. E. Huheey. 2001. "Reptiles and Amphibians of the Smokies." Great Smoky Mountains Natural History Association.
Mead, L. S., S. G. Tilley, and L. A. Katz. 2002. "Genetic structure of the Blue Ridge dusky salamander (Desmognathus orestes): Inferences from allozymes, mitochondrial DNA and behavior." Evolution 55: 2287–2302.
Anderson, J., and S. G. Tilley. 2003. "Systematics of the Desmognathus ochrophaeuscomplex in the Cumberland Plateau of Tennessee." Herpetological Monographs, 17: 75–110.
Tilley, S. G., R. L. Eriksen, and L. A. Katz. 2008. "Systematics of dusky salamanders, Desmognathus (Caudata: Plethodontidae), in the mountain and Piedmont regions of Virginia and North Carolina, USA." Zoological Journal of the Linnaean Society 152: 115–30.