Co-occurrence and Hybridization between Necturus maculosus and a Heretofore Unknown Necturus in the Southern Appalachians

The only mudpuppy (Caudata: Proteidae) known to occur in the Tennessee Valley of the Interior Highlands and Southern Appalachians is the Common Mudpuppy (Necturus maculosus). Necturus maculosus is not known to co-occur with any other congeners. Here, we report evidence that an additional Necturus occurs in the Hiwassee River, a tributary of the Tennessee River, in eastern Tennessee. Some specimens from the Hiwassee River are clearly identified as N. maculosus, but others resemble the Neuse River Waterdog (N. lewisi), known from only the Tar-Neuse river system draining to the Atlantic Ocean on the opposite side of the Appalachian Mountains. Concordance between color pattern, mitochondrial DNA, and four nuclear loci demonstrate that these two co-occurring forms represent distinct lineages rather than color variants within a single, panmictic population. A few mismatched genotypes (7 of 32 individuals in total) suggest rare hybridization and backcrossing. Phylogenetic analyses indicate that the new form (hereafter N. aff. lewisi) is related to N. lewisi and N. punctatus (both species from the Atlantic Coastal Plain and Piedmont), but whether this population was introduced, is a naturally disjunct population of N. lewisi, or a heretofore unknown species is yet unclear. Regardless, its existence raises new questions about the evolutionary and ecological dynamics of riverine salamander communities in southern Appalachia and for conservation and management.