AmphibiaWeb - Desmognathus imitator
AMPHIBIAWEB
Desmognathus imitator
Imitator Salamander
Subgenus: Desmognathus
family: Plethodontidae
subfamily: Plethodontinae

© 2011 Michael Graziano (1 of 29)
Conservation Status (definitions)
IUCN (Red List) Status Least Concern (LC)
NatureServe Status Use NatureServe Explorer to see status.
CITES No CITES Listing
National Status None
Regional Status None
Access Conservation Needs Assessment Report.

   

 

View distribution map in BerkeleyMapper.
View Bd and Bsal data (24 records).

Description
Desmognathus imitator is a medium-sized desmognathine salamander, with total length reaching up to 70 mm for adult males and up to 100 mm for adult females (Dodd 2004). The tail is cylindrical (Dunn 1927) and lacks a keel (Petranka 1998). This species has 14 costal grooves (Dunn 1927). Like other desmognathines, it has a light line running from the eye to the posterior angle of the jaw (Dodd 2004). The dorsum is brown to nearly black, generally with an indistinct dorsal band composed of a wavy dark brown stripe (Dodd 2004). The belly is gray-black (Dunn 1927; Petranka 1998). Red cheek patches are often present (Dunn 1927; Petranka 1998). Toe tips are not cornified (Petranka 1998).

Variation: Cheek spots may be reddish, orangish, or yellowish (Petranka 1998). Melanistic forms are also seen, with the dorsal surfaces mostly grayish black (Petranka 1998). Individuals of D. imitator lacking cheek spots are morphologically indistinguishable from D. ocoee and can be distinguished only by courtship behavior and molecular evidence (Petranka 1998). Another form was found at Waterrock Knob, N.C. in 1981; individuals from this locality have paired red dorsal spots and a mottled greenish background coloration that matches their wet, vertical rock habitat (Tilley 2000).

Larvae are dark-colored, with distinct lighter dorsal spots ranging from orange to chestnut in color. They may have clearly visible cheek patches (Dodd 2004).

Similar species: In some localities, D. imitator cannot be easily distinguished from the sympatric species D. ocoee; in other localities, these two species have differing color patterns, with D. imitator lacking the distinct light to dark brown dorsal bands that generally characterize D. ocoee, and having red cheeks (lacking in D. ochrophaeus) (Tilley et al. 1978). In the Great Smokies, it can be difficult to distinguish older individuals of D. imitator from older individuals of D. conanti, D. santeetlah, and D. ocoee, as they may all be a uniform darker color (Dodd 2004). For individuals in the Great Smokies that are not uniformly dark, D. imitator can be distinguished from D. ocoee by the lack of a straight edge on the dorsal stripe (vs. presence of a straight edge on the dorsal stripe for D. ocoee); from D. santeetlah by the lack of a light yellow wash on the underside of the limbs and tail (vs. yellow wash present on the underside of limbs and tail for D. santeetlah; and from D. conanti by a black belly and having the tail rounded in cross-section (vs. grayish salt-and-pepper belly and having the tail keeled in cross-section for D. conanti) (Dodd 2004).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: United States

U.S. state distribution from AmphibiaWeb's database: North Carolina, Tennessee

 

View distribution map in BerkeleyMapper.
View Bd and Bsal data (24 records).
This species has a restricted distribution, occurring in the Great Smoky Mountains in southeastern Tennessee and southwestern North Carolina, and in the Balsam Mountains and the Plott Balsam Mountains in North Carolina at elevations ranging from 900 to 2024 m (Dunn 1927; Tilley 2000). It is found in pine forests under the leaf litter and along small streams (Dunn 1927). The population at Waterrock Knob, Plott Balsam Mountains, inhabits wet rock faces at 1650-1800 m asl, and populations phenotypically distinct from the Waterrock Knob group occupy wet rock faces on Balsam Mountain, along the Blue Ridge Parkway (Tilley 2000; Lannoo 2005).

Life History, Abundance, Activity, and Special Behaviors

This salamander is nocturnal, emerging from hiding places to forage at night (Verrell and Mabry 2000). It can be found along streams and in seepages but is also found on the forest floor well away from water (Dodd 2004).

Desmognathus imitator is sympatric with the very similar-appearing D. ocoee in parts of their ranges, in the Great Smoky Mountains of North Carolina and Tennessee. In some localities, the two species have different color patterns, while in others they cannot be easily distinguished morphologically; however, studies have shown that introgression and hybridization have not occurred (Tilley et al. 1978; Verrell and Tilley 1992). Verrell (1989) conducted experimental crosses at a locality where the two species could be distinguished by color pattern, and found that males of these two sympatric species generally failed to initiate even the beginning stages of courtship with heterospecific females, and that the mechanism of reproductive isolation involved differing olfactory chemical stimuli.

Courtship is similar to that of other species of similar body size in the genus Desmognathus and has been described by Verrell and Tilley (1992) and Verrell (1994), Phases of courtship behavior include orientation of the male to the female, male persuasion of the female (using both tactile and chemical stimuli), and indirect sperm transfer by means of a spermatophore. The male approaches the female, who initially may flee. The male "butterflies" the forelimbs and, once the female remains still, engages in head-rubbing. Periodically, the male slides beneath the female's chin while undulating his tail, and also moves to the female's posterior to snap or pull with his snout, presumably delivering mental gland secretions. After some time, the female will straddle the male's tail and the pair walks along, until the spermatophore is deposited by the male and picked up by the female. The duration of courtship from head-rubbing to the initiation of the tail-straddle walk is 180-215 minutes. It has also been reported that some encounters include a "bite-and-seize" behavior, where the male suddenly seized the female with his mouth after repeated follow-and-approach tries by the male, eventually followed by release of the female and continuation of courtship (Verrell and Mabry 2000).

Gravid females have been captured from June to early August (Dodd 2004). Eggs are creamy white in color, and are deposited in a monolayered (more common) or bilayered cluster in seepage areas, under moss or debris, or in the crevices between rocks (Bernardo 2000; Koenings et al. 2000). Clutches have also been found attached to the undersides of rocks in water-saturated gravel in a spring (Lannoo 2005). Clutches range in size from 13-30 eggs, with each egg measuring 3.5 mm in diameter (Koenings et al. 2000). Females tend their eggs (Dodd 2004). Larvae are thought to transform after about 9-10 months (Dodd 2004). Desmognathus imitator is nontoxic and is thus considered a Batesian mimic of the red-cheeked and unpalatable species Plethodon jordani, with whom it is sympatric (Brodie and Howard 1973). Red-cheeked morphs of D. imitator are common in populations sympatric with P. jordani (Tilley et al. 1978).

Trends and Threats
D. imitator (along with the closely related D. ocoee has been found to be significantly more abundant in undisturbed habitat (Hyde and Simons 2001). Disease may possibly be a threat; Gray et al. (2009) found a high prevalence of ranavirus infection (85%) in their small study sample (n=13) from the Great Smoky Mountains National Park, Tennessee. Acidification of soils and streams at high-elevation sites, from pollutants in the form of acid rain, may be a threat (Petranka 1998). Nearly the entire range lies within the Great Smoky Mountains National Park and the Blue Ridge Parkway (Lannoo 2005). The phenotypically distinct Waterrock Knob population has a very restricted range and is also vulnerable due to proximity to a well-trafficked road (Hammerson 2004).

Possible reasons for amphibian decline

Urbanization
Disturbance or death from vehicular traffic
Local pesticides, fertilizers, and pollutants
Long-distance pesticides, toxins, and pollutants

Comments
Species authority: Dunn (1927).

Etymology: The generic name Desmognathus derives from the Greek word desmos, meaning "ligament," and gnathos, meaning "jaw." It refers to the visibly enlarged bundle of ligaments on the sides of the heads of these salamanders. The specific name imitator refers to the fact that its red cheeks mimic those of the sympatric species Plethodon jordani (Dodd 2004).

Initially this species was described as a subspecies of D. fuscus (Dunn 1927). Subsequently, Tilley et al. (1978) examined genetic variation in populations of D. ochrophaeus in the southern Appalachians, and found that allozyme differences revealed two sympatric forms in the Great Smoky Mountains of Tennessee and North Carolina, with color patterns being identical in some localities. The more widely distributed form was retained as D. ochrophaeus (subsequently referred to as D. ocoee) while the form restricted to the Great Smoky Mountains was recognized as D. imitator (Tilley et al. 1978). The rock-face dwelling form at Waterrock Knob has a different coloration than other populations of D. imitator (Tilley 1985) and is genetically differentiated from streamside and forest populations (Petranka 1998).

Desmognathus imitator is part of the D. ochrophaeus complex and may itself include more than one species (Tilley 1985; Verrell and Tilley 1992).

References

Bernardo, J. (2000). ''Early life histories of dusky salamanders, Desmognathus imitator and D. wrighti, in a headwater seepage in Great Smoky Mountains National Park, USA.'' Amphibia-Reptilia, 21, 403-407.

Brodie, E. D. Jr., and Howard, R. R. (1973). ''Experimental study of Batesian mimicry in the salamanders Plethodon jordani and Desmognathus ocrophaeus.'' The American Midland Naturalist, 90, 38-46.

Dodd, C. K. (2004). The Amphibians of Great Smoky Mountains National Park. The University of Tennessee Press, Knoxvile, Tennessee.

Dunn, E. R. (1927). ''A new mountain race of Desmognathus.'' Copeia, 1927(167), 84-86.

Gray, M. J., Miller, D. L., and Hoverman, J. T. (2009). ''First report of Ranavirus infecting lungless salamanders.'' Herpetological Review, 40, 316-319.

Hammerson, G. (2004). Desmognathus imitator. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2. www.iucnredlist.org. Downloaded on 16 January 2012.

Hyde, E. J., and Simons, T. R. (2001). ''Sampling plethodontid salamanders: sources of variability.'' The Journal of Wildlife Management, 65, 624-632.

Koenings, C. A., Smith, C. K., Domingue, E. A., and Petranka, J. W. (2000). ''Natural history notes: Desmognathus imitator (Imitator Salamander). Reproduction.''

Lannoo, M. J. (2005). Amphibian Declines: The Conservation Status of United States Species. University of California Press, Berkeley.

Tilley, S. G. (1985). ''Desmognathus imitator.'' Catalogue of American Amphibians and Reptiles, 359, 1-2.

Tilley, S. G. (2000). ''The systematics of Desmognathus imitator.'' The Biology of Plethodontid Salamanders. R. C. Bruce, R. Jaeger, and L. D. Houck, eds., Kluwer Academic/Plenum Publishers, New York, New York, 121-147.

Tilley, S. G., Merritt, R. B., Wu, B., and Highton, R. (1978). ''Genetic differentiation in salamanders of the Desmognathus ochrophaeus complex (Plethodontidae).'' Evolution, 32, 93-115.

Verrell, P. A. (1989). ''An experimental study of the behavioral basis of sexual isolation between two sympatric species of plethodontid salamanders Desmognathus imitator and D. ochrophaeus.'' Ethology, 80, 274-282.

Verrell, P. A. (1994). ''Courtship behaviour of the salamander Desmognathus imitator (Amphibia: Caudata: Plethodontidae).'' Amphibia-Reptilia, 15, 135-142.

Verrell, P. A., and Mabry, M. (2000). ''The courtship of plethodontid salamanders: form, function and phylogeny.'' The Biology of Plethodontid Salamanders. R. C. Bruce, R. G. Jaeger, and L. D. Houck, eds., Kluwer Academic/ Plenum Press, New York, NY.

Verrell, P. A., and Tilley, S. G. (1992). ''Population differentiation in plethodontid salamanders: divergence of allozumes and sexual compatibility among populations of Desmognathus imitator and D. ochrophaeus (Caudata: Plethodontidae).'' Zoological Journal of the Linnean Society, 104, 67-80.



Originally submitted by: Kellie Whittaker and Deborah Lee (first posted 2010-07-14)
Edited by: Kellie Whittaker (2012-01-18)

Species Account Citation: AmphibiaWeb 2012 Desmognathus imitator: Imitator Salamander <https://amphibiaweb.org/species/3922> University of California, Berkeley, CA, USA. Accessed Sep 17, 2021.



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Citation: AmphibiaWeb. 2021. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 17 Sep 2021.

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