Hiding in Plain Site: Southern Dusky Salamanders


Southern Dusky Salamander- Photo: Houston

Last year on a warm sticky day in June, we ventured into a large perennial seep at the base of a small sandhill.  There are similar seeps all over the southeast where groundwater trickles out onto the surface and forms small mucky swamps that are rarely more than a few inches deep.  Seeps provide important habitat for many species of amphibians and reptiles and several of the salamander species native to the Coastal Plain can frequently be found amongst the muck and leaf litter.  It just so happens that on this day we were searching for dusky salamanders (genus Desmognathus), which had been caught in this location previously but had not been satisfactorily identified.

In the Coastal Plain of Georgia, identifying dusky salamanders is easier said than done.  The most widespread species currently described is Desmognathus auriculatus (Southern Dusky Salamander).  However, recent genetic analyses have shown that throughout its range this single described species is represented by at least two distinct species (Means et al. 2017) and that there remains large uncertainty surrounding several of the Atlantic Coast lineages (Beamer and Lamb 2008).  To complicate matters, the range of D. conanti (Spotted Dusky Salamander) also extends along several major river drainages into the Coastal Plain.  It remains unclear how widely distributed this species is along these drainages. Furthermore, both D. auriculatus and D. conanti can be extremely variable in appearance and are difficult to distinguish from one another in the field.

Small serpage fed creek- Photo: Houston

The difficulty with field identification and the need for more clarity regarding Atlantic Coast lineages of D. auriculatus meant that collecting tissue samples from dusky salamanders at new locations in Georgia could be very useful.  Thus, we found ourselves wading around in black muck and fighting the biting insects in search of the same salamanders that had been seen at this site in previous years.  The water in the seep was barely more than a trickle before flattening out into a handle of slightly larger pools. There was abundant leaf litter and woody debris to flip, and I knew our chances of finding salamanders was pretty high.  Sure enough, after searching through leaf litter, scooping muck up onto the bank, and turning logs, we were able to catch two Desmognathus salamanders, but the question remained: which species did they belong to?  To find the answer, we needed to collect tissue samples from both individuals, which was easily accomplished by clipping the end of the salamander’s tail into a small vial of ethanol.  Samples in hand, we retreated out of the seepage swamp with the knowledge that we would know for sure which species we had just documented in the near future.

The downside to shipping off DNA samples to confirm identifications is that it can take several weeks for results to come back.  Eventually, we received test results from Dr. Jennifer Lamb (Southeastern Louisiana University). The two salamanders we captured did in fact belong to the D. auriculatus group, but they were members of one of the Atlantic Coast clades that could possibly represent their own species.  Interestingly, the salamanders were members of clade C2 that had previously only been known from South Carolina. Thus, these individuals provided the first documented county record for Candler County, Georgia and a range extension into GA for the C2 clade of D. auriculatus.  This distribution note was published in the most recent volume of Herpetological Review, and we are planning to collect additional tissue samples when the opportunity arises to further elucidate the taxonomy of D. auriculatus.

Literature Cited

Beamer, D. A., and T. Lamb. 2008. Dusky salamanders (Desmognathus, Plethodontidae) from the Coastal Plain: Multiple independent lineages and their bearing on the molecular phylogeny of the genus. Molecular Phylogenetics and Evolution 47:143–153.

Means, D. B., J. Y. Lamb, and J. Bernardo. 2017. A new species of dusky salamander (Amphibia: Plethodontidae: Desmognathus) from the Eastern Gulf Coastal Plain of the United States and a redescription of D. auriculatus. Zootaxa 4263:467–506.