A new, narrowly endemic species of swamp-dwelling dusky salamander (Plethodontidae: Desmognathus) from the Gulf Coastal Plain of Mississippi and Alabama

We describe a new, narrowly endemic species of swamp-dwelling dusky
salamander (Plethodontidae: Desmognathus pascagoula sp. nov.) from the
Gulf Coastal Plain of southeastern Mississippi and southwestern Alabama
based on linear morphometrics, mitochondrial DNA, and single nucleotide
polymorphisms from 881 loci produced using genotype-by-sequencing. Some
populations of the new species were historically referred to as D.
auriculatus, a polyphyletic assemblage of at least three species in the
Atlantic and Gulf Coastal Plain from Texas to North Carolina. Populations
of D. auriculatus from the Gulf Coastal Plain in Louisiana and Mississippi
were recently described as D. valentinei. The new species includes
populations that were tentatively referred to D. valentinei, but we find
it is morphologically, genetically, and geographically distinct. It is
smaller, has a more defined dorsal color pattern, more irregular whitish
“portholes” in up to three rows on the lateral surfaces of the body and
tail, and a brighter orange or yellowish orange postocular stripe. At
present, the new species is known from only six extant populations in the
lower Pascagoula, Escatawpa, and Mobile drainages. The latter represents a
distinct phylogeographic lineage. We also refer a historical collection
from the northeastern side of the Mobile-Tensaw River Delta to this
species, suggesting a much broader range in the past. We suspect that more
populations remain to be discovered in the area, and their potential
species-level distinctiveness should be tested further. This discovery
increases knowledge of the biodiversity in the southeastern United States
Coastal Plain, a candidate region meeting the global criteria for a
“biodiversity hotspot,” and underscores the amount of cryptic diversity
likely remaining to be discovered and described in Nearctic salamanders.