Amphibians of North Carolina
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Desmognathus marmoratus (Moore, 1899) - Northern Shovel-nosed Salamander


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Taxonomy
Class: Amphibia Order: Caudata Family: Plethodontidae Subfamily: Plethodontinae Author: (Moore, 1899)
Taxonomic Comments: Members of the genus Desmognathus are commonly known as dusky salamanders because of their overall dark brown or dusky ground color. Like many plethodontid salamanders, they have proven to be a taxonomically challenging group that contains several species complexes. Kozak et al. (2005) documented 35 major lineages in the eastern US, even though only 22 species were formally recognized by taxonomists in 2021. This suggests that there are numerous cryptic species that remain to be described. A more recent comprehensive molecular survey of populations in the eastern US by Beamer and Lamb (2020) indicate that at least 45 major lineages or clades are present.

Herpetologists have traditionally recognized the Shovel-nosed Salamander (D. marmaratus) as a species that closely resembles the Black-bellied Salamander (D. quadramaculatus) in being a relatively large Desmognathus with a stocky build, keeled and laterally compressed tail, cornified toe-tips and two rows of light spots that are usually present along each side of the body. It differs from the Black-bellied Salamander in having internal nares that form slits rather than round pores, in the coloration and patterning on the venter of adults, and in the profile of the head. Recent molecular studies by Beamer and Lamb (2020), as well as several previous studies, have shown that these two species are not monophyletic. Instead, populations of both species are interspersed within a strongly supported clade that contains all populations of D. quadramaculatus, D. marmoratus, and a third species, D. folkertsi. This major clade contains two subclades, including one that includes all D. quadramaculatus populations sampled south of the Pigeon River, as well as all D. marmoratus populations sampled in the Apalachicola and Savannah River drainages. The second subclade includes all populations of D. quadramaculatus sampled from east of the Tuckasegee River drainage basin (with one exception) as well as all populations of D. marmoratus sampled outside the Apalachicola and Savannah River drainages. In some cases populations of D. quadramaculatus are more similar genetically to D. marmoratus than to other D. quadramaculatus populations. Collectively, the research by Beamer and Lamb (2020) and others indicates the presence of a species complex that involves all three currently recognized species. After conducting additional molecular and morphometric studies, Pyron and Beamer (2022) recognized five species within the Black-bellied Salamander complex. These include a previously recognized species D. folkertsi, and four new species (D. amphileucus, D. gvnigeusgwotli, D. kanawha and D. mavrokoilius) that replace what was traditionally known as D. quadramaculatus and certain populations of D. marmoratus.

From a taxonomic standpoint, Jones et al. (2006) conducted additional mitochondrial studies that built upon the work of Kozak et al. (2005) and others, and concluded that there were three groups of shovel-nosed salamanders that might merit species recognition. However, they did not formally recognize these due to certain unresolved phylogenetic issues. In a French work, Dubois and Raffaëlli (2012) did elect to formally recognized three species as D. aureatus, D. melanius, and D. marmoratus) based on Jones et al.'s (2006) and others work, but their taxonomic changes were not widely adopted by North American herpetologists. In the most recent work, Pyron and Beamer (2023) provide a comprehensive review of the literature, correct a nomenclatural error by Dubois and Raffaëlli (2012), and provide a systematic revision of three species of shovel-nosed salamanders that are currently recognized.

All three of the currently recognized shovel-nosed salamanders occur in North Carolina and include, 1) the Southern Shovel-nosed Salamander (D. aureatus) that occurs in northeastern Georgia, northwestern South Carolina, and small portions of the nearby border regions of North Carolina, 2) the Western Shovel-nosed Salamander (D. intermedius) that occurs in the Blue Ridge of western North Carolina and eastern Tennessee, and appears to be restricted to the Tennessee drainages of major rivers in the central and southern Blue Ridge of North Carolina, and 3) the Northern Shovel-nosed Salamander (D. marmoratus) that occurs from northeast of the Pigeon River in North Carolina to northeastern Tennessee and southwestern Virginia. These three species do not represent a natural group as previously thought, but instead exhibit convergent phenotypes across multiple species, potentially driven by ancient episodes of adaptive introgression between ancestral lineages. Although there are some morphometric differences between species that are best determined using museum specimens, the three species are best identified in the field by using their geographic ranges and the site where a specimen was observed.
Species Comments:
Identification
Description: This is a large Desmognathus species (SVL of adults around 30 – 75 mm) that closely resembles members of the D. quadramaculatus complex, particular D. mavrokoilius that is sympatric with it. The dorsal ground color of the adults is dark brown and is mottled with numerous golden-brown to reddish-brown marks that are rather indistinct. The markings lack light-colored centers, and two rows of light spots are usually present along each side of the body. The venter is light colored in subadults, but becomes dark brown or dark gray in the adults. The adult males lack vomerine teeth, while the females have very few (Pyron and Beamer, 2023). The head is flattened, and the internal nares form slits rather than round pores as seen in other Desmognathus species. The toe tips are cornified and blackish. The males are larger on average, have enlarged maxillary teeth, papillate cloacae (smooth in females), and an inconspicuous mental gland (Martof 1962, Petranka 1998).

The adults of D. marmoratus are most easily confused with D. mavrokoilius, in part because Pyron et al. (2022) found that D. marmoratus had varying levels of D. mavrokoilius genes incorporated into its genome at numerous sample sites. It is uncertain if this reflect past or present introgression. Desmognathus marmoratus tends to have a dark gray belly, often with a lighter central area with reduced pigmentation. The venter of adult D. mavrokoilius is often not as black as other black-bellied salamanders and is more mottled with grayish or salt-and-pepper ventral coloration, which adds to the confusion. The dorsal ground color of D. marmoratus is typically dark brown versus the greenish, olive, or yellowish background of D. mavrokoilius. Martof (1962) listed a series of characters that are useful in separating shovel-nosed salamanders from other large Desmognathus, the most reliable being the shape of the internal nares. They also have a proportionately shorter tail with a more prominent tail fin that is often more ragged. The adults of D. marmoratus move slowly away when disturbed, in contrast to the rapid fleeing characteristic of D. mavrokoilius (Pope 1924, Martof 1962, Bishop 1924). This behavioral difference is often useful in identifying specimens in the field.

The larvae and juveniles of this species are difficult to distinguish from those of the members of the D. quadramaculatus complex in the field. The hatchlings average around 11 mm SVL. They have two rows of light spots on the dorsum and closely resemble the hatchlings of members of the D. quadramaculatus complex.
Online Photos:    Google   iNaturalist
Observation Methods: The subadults and adults are most easily found by searching the riffle sections of small to medium-sized streams. Kick-netting is an effective way to collect the animals.
AmphibiaWeb Account
Distribution in North Carolina
Distribution Comments: The Northern Shovel-nosed Salamander prefers cool, well oxygenated, high-gradient streams and reaches its southern limits in northeastern Transylvania County, Yancey County, McDowell County and northern Rutherford County. From there, the range extends northward through western North Carolina and northeastern Tennessee to southwestern Virginia. Populations are patchily distributed and may be absent from some of the drainages in this region (Petranka 1998; Pyron and Beamer, 2023). They are more likely to be found at lower to mid-elevations in the mountains, and are restricted to the Blue Ridge and Blue Ridge Escarpment. Populations are known from the South Fork of the Holston, the Watauga, and the Nolichucky (Upper Tennessee) and the Upper Broad and Upper Catawba (Santee) River drainages. A disjunct population also occurs in Raleigh County, West Virginia in the Lower New (Kanawha) River drainage (Pyron and Beamer, 2023).
County Map: Clicking on a county returns the records for the species in that county.
GBIF Global Distribution
Key Habitat Requirements
Habitat: The Northern Shovel-nosed Salamander is an almost entirely aquatic species that prefers cool, well oxygenated streams at elevations of approximately 450–1600 m (1476-5,250'; Pyron and Beamer, 2023). This species is generally more common in second and third-order streams in the southern Appalachians at elevations below 1220 m (4000'). Adults reach their highest densities in small to medium-sized streams with broken rocks and loose gravel, but local populations can also be found in headwater streams with gentle gradients (Martof 1962, Petranka 1998). Shallow riffle areas in streams that have angular rocks, loose gravel and moderate to fast flowing water provide ideal microhabitats for the juveniles and adults.
Environmental and Physiological Tolerances: Although poorly documented, this species appears to be intolerant of relatively warm, heavily silted, or poorly oxygenated streams. The environmental tolerances of this species are likely very similar to those of trout in western North Carolina.
See also Habitat Account for Montane Perennial Creeks and Small Streams
Life History and Autecology
Breeding and Courtship: Information on the breeding season and courtship behavior are not available.
Reproductive Mode: Females lay their eggs as water temperatures rise in late spring or early summer and remain with their clutches through hatching (Petranka 1998). Pope (1924) found 28 eggs with late-term embryos on 6 August in Boone Fork near Grandfather Mountain. The eggs were attached singly in two layers to the edge of a submerged stone, and also were in fast-flowing water. Freshly laid eggs are unpigmented, about 4 mm in diameter, and are surrounded by a transparent capsule attached by a short peduncle (Pope 1924).

Aquatic Life History: The hatchlings are weak swimmers and often wash downstream into pools with low current. This species is one of the most aquatic of our Desmognathus species and rarely leaves the water. Data on the life history of the larvae, subadults and adults is largely lacking. The juveniles remain in the stream proper where they occupy habitats similar to those of the adults. Both are frequently found beneath submerged stones in fast current and often rest during the day with their heads protruding from under stones. They often emerge after dark and move about, presumably in search of food and mates. Specimens are most abundant in shallow rapids and riffles. The diet is largely unknown, but the larvae, juveniles, and adults likely feed mostly on the larval stages of aquatic insects such as mayflies and caddisflies, as is the case for the better-studied Southern Shovel-nosed Salamander.

General Ecology
Community Ecology: This species commonly coexists with fishes, crayfishes, and other large salamanders that are potential competitors or predators, but ecological interactions with these are largely undocumented.
Adverse Environmental Impacts
Effects of Introduced Species/Induced Increases of Native Species: The introduction of non-native trout into streams in western North Carolina has undoubtedly resulted in many losses of the larvae and adults due to predation (Martof, 1962).
Status in North Carolina
NHP State Rank: S4
Global Rank: G4
Status Comments: This southern Appalachian endemic is mostly found in the northern half of the Blue Ridge in North Carolina and adjoining areas of eastern Tennessee. . Desmognathus marmoratus can be locally common and is mostly found on national forests or other lands that provide a significant degree of protection, particularly where stream buffers are maintained. Local populations are common throughout the range and can reach high densities in lower-order streams.
Stewardship: This and other stream-breeding salamanders in the Blue Ridge prefer high-quality streams with minimal siltation and wide buffers of mature or old-growth hardwoods.

Photo Gallery for Desmognathus marmoratus - Northern Shovel-nosed Salamander

3 photos are shown.

Recorded by: Max Ramey, Eric Johnson
Watauga Co.		Recorded by: Max Ramey
Avery Co.
Recorded by: Jim Petranka
None Co.
Comment: Range map for shovel-nosed salamanders based on genetically identified specimens (courtesy of Alex Pyron).