Amphibians of North Carolina
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Plethodontidae Members:
NC Records

Desmognathus imitator - Imitator Salamander


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Taxonomy
Class: Amphibia Order: Caudata Family: Plethodontidae Subfamily: Plethodontinae
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. (2006b) 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.

In North Carolina, a group of medium-sized dusky salamanders with rounded, unkeeled tails (D. carolinensis, D. imitator, D. ocoee, and D. orestes) have been treated as members of an informal cryptic species complex known as the D. ochrophaeus complex (Tilley and Mahoney 1996). The members of this group are commonly referred to as mountain dusky salamanders, and were previously treated as a single species (D. ochrophaeus, sensu lato) before being split. The most recent molecular study based on mtDNA sequence data (Beamer and Lamb 2020), as well as previous studies (see Beamer and Lamb 2020), indicate that there are many additional clades within the D. ochrophaeus complex that may represent undescribed cryptic species. In addition, certain forms appear to be more genetically similar to D. fuscus than to other members of the D. ochrophaeus complex. Some of the highlights of this study are that 1) Populations currently referred to as D. carolinensis do not appear to constitute a genetically distinct lineage and instead cluster with 39 populations of D. fuscus, 2) Populations currently referred to as D. ocoee contain several clades that may reflect additional cryptic species; in some cases these clades contain mixtures of populations that are currently referred to as D. ocoee, D. conanti and D. apalachicolae, 3) Populations currently referred to as D. orestes contain three clades, one of which is sister to a clade containing D. ochrophaeus and other clades of D. orestes, and 4) Populations currently referred to as D. imitator constitute a well-defined clade that is not closely related to other members of the D. ochrophaeus complex and should not be treated as a member of that complex.

Populations of D. imitator from higher elevations along the Blue Ridge Parkway in Haywood and Jackson counties are morphologically and genetically distinct based on protein patterns from those in the Smokies (Tilley 2000). However, Beamer and Lamb (2020) found relatively low levels of mtDNA divergence across the range of D. imitator, which conflicts with evidence based on protein banding profiles. The Haywood and Jackson County form is currently considered to be conspecific with D. imitator and is treated as such here.
Species Comments:
Identification
Description: Desmognathus imitator is a medium-sized Desmognathus that has a gray venter and an unkeeled tail that is rounded to oval shaped in cross-section. The tail is slightly longer than the body, and the toe tips lack cornifications as seen in some of the more aquatic Desmognathus species. The dorsum often has a wavy dorsolateral stripe, but melanistic individuals that are mostly grayish black above are common. Adults range from about 7-11 cm TL and there are normally 14 costal grooves.

Desmognathus imitator often coexists locally with D. ocoee and the two are difficult to tell apart. The former is a Batesian mimic of Plethodon jordani and most local populations of D. imitator have a small percentage of individuals with yellowish, orangish, or reddish cheek patches. Morphs of D. imitator with colored cheeks may comprise as much as 15-20% of local populations (Tilley et al. 1978). Because morphs of D. ocoee with colored cheek patches do not occur within the range of D. imitator, any specimen collected with colored cheeks within D. imitator's range can be confidently assigned to that species.

In many populations, specimens of D. imitator that lack colored cheeks are morphologically indistinguishable from D. ocoee. These can only be identified reliably using molecular markers (Petranka 1998, Tilley 1985, Tilley et al. 1978). At sites along the crest of the Great Smoky Mountains, the two species can be distinguished with some degree of reliability by color pattern and the presence of dorsal bands. Desmognathus imitator typically has an indistinct dorsal band with strongly undulating edges, while sympatric D. ocoee has a more distinct dorsal band with straight to moderately undulating edges (Tilley 1985, Tilley et al. 1978). However, there are numerous exceptions and molecular markers provide the most reliable way to identify specimens. In addition, melanistic specimens are common in both species and are difficult to identify to species based on external traits.
Technical Reference: Tilley (1985); Tilley et al. (1978)
Online Photos:    Google   iNaturalist
AmphibiaWeb Account
Distribution in North Carolina
Distribution Comments: Desmognathus imitator is restricted to forested, streamside habitats in the Great Smoky Mountains, Balsam Mountains, and Plott Balsam Mountains of eastern Tennessee and western North Carolina. Populations can be found at elevations of 900-2024 m. The range extends from the Smokies to just east of Soco Gap on Balsam Mountain. This species is generally found closer to streams and seepages than syntopic populations of D. ocoee (Tilley et al. 1978). The Imitator Salamander is also more common at lower elevations than is D. ocoee.
Distribution Reference: Tilley et al. 1978, Tilley 1985
County Map: Clicking on a county returns the records for the species in that county.
GBIF Global Distribution
Key Habitat Requirements
Habitat: Imitator Salamanders are ecologically similar to members of the Mountain Dusky Salamander complex and co-occur with the Ocoee Salamander in portions of the Great Smoky Mountains and neighboring high elevation ridges (Beane et al. 2010, Petranka 1998). Adults are semi-terrestrial and are associated with mid- to high-elevation forests. In the Great Smoky Mountains, they occur at elevations above 914 m (Tilley and Hughey 2004). They are usually found close to streams and seeps, but can be found on mesic rock faces in some areas. Breeding takes place in seepages and headwater streams where the larvae undergo a period of aquatic development.
See also Habitat Account for Montane Mesic Forests with Seepages/Headwater Streams
Life History and Autecology
Breeding and Courtship: The mating seasonal is undocumented for D. imitator, but probably involves both autumn and spring breeding as is the case for many small Desmognathus species. Courtship is essentially indistinguishable from that of members of the D. ochrophaeus complex and involves a period of sexual persuasion followed by a tail straddle walk (Verrell 1994e, Verrell and Tilley 1992).

In paired trials, courtship begins when a male begins to actively pursue a female. The male may butterfly the forelimbs as he get close to the female. This involves synchronously rotating the forelimbs in a manner that is similar to the butterfly stroke of a swimmer. Eventually the female stops fleeing and the male engages in head rubbing bouts that may lasts as long as six minutes, accompanied by occasional butterflying. The male interupts head rubbing periodically and moves to the female's back region and pulls or forcefully snaps with his snout. The male may also slide beneath the female's chin while undulating his tail, then curl his body backwards and forcefully snap his snout on the female's back. Snapping and pulling lacerates the skin and vaccinates the female with secretions from the male's mental gland. Verrell (1994e) observed two instances in which a male held the female in his jaws for 1-18 minutes. This behavior has also been recorded in D. wrighti and D. aeneus (Petranka 1998) and presumably functions to transfer mental gland secretions to the female. The female eventually straddles the male's tail and the pair engages in a stereotypic tail-straddle walk that is followed by spermatophore deposition and pickup.
Reproductive Mode: Because of the difficulty in distinguishing D. imitator from D. ocoee in the field, most aspects of the life history of this species have not been studied. The general life cycle is presumably similar to that of D. ocoee with mating occurring during the fall and spring months and oviposition occurring in late spring and early summer. Steve Tilley found a clutch of eggs on 21 June beneath the surface of a spring in North Carolina that were in all likelihood those of D. imitator (Petranka 1998). Koenings et al. (2000) found six clutches and brooding females on 30 June 1998 in Swain Co. in saturated soil in a seepage area. The eggs were in early developmental stages and were cream colored and attached in a monolayer to the underside of flat rocks that were embedded in the soil. One clutch had a small number of eggs arranged in a bilayer, and two of the clutches were deposited within 22 cm of each other but were on separate rocks. The clutch sizes for five nests ranged from 13-24 eggs (mean = 19) and the eggs varied from 3.0-4.0 mm in diameter. Two other clutches illustrated by Petranka (1998) are from the same site and contained 23 and 30 eggs.
General Ecology
Adverse Environmental Impacts
Status in North Carolina
NHP State Rank: S3
Global Rank: G3G4
Status in North Carolina: W2

Photo Gallery for Desmognathus imitator - Imitator Salamander

3 photos are shown.

Recorded by: Jim Petranka
Swain Co.
Comment: A melanistic adult.		Recorded by: Jim Petranka
Swain Co.
Recorded by: Jim Petranka
Swain Co.
Comment: Two clutches of eggs on the underside of rock.