Amphibians of North Carolina
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Plethodontidae Members:
NC Records

Plethodon amplus - Blue Ridge Gray-cheeked Salamander



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Taxonomy
Class: Amphibia Order: Caudata Family: Plethodontidae Subfamily: Plethodontinae
Taxonomic Comments: The Plethodon jordani complex is a group of closely related forms that mostly are found at higher elevations in the southern Appalachian Mountains. Because they are largely restricted to mid to higher elevations and are absent from valleys, they form a series of geographic isolates that have diverged from one another to varying degrees. Depending on geographic location, the adults may be unmarked, or have red cheeks, red legs, or brassy frosting on their backs. Members of this group were traditionally treated as a single, geographically variable species known as Jordan's Salamander (Plethodon jordani). Hairston (1950) recognized seven subspecies of P. jordani, but Highton (1962) rejected these because some characters do not vary concordantly among the recognized taxa. In later papers, Highton (1970, 1972) recognized 12 geographic isolates in southern populations and argued that recognizing subspecies would serve no useful purpose.

Molecular studies (Highton and Peabody 2000, Weisrock and Larson 2006) have since revealed the presence of seven major evolutionary lineages that are now recognized as separate species (P. amplus, P. cheoah, P. jordani (sensu stricto), P. meridianus, P. metcalfi, P. montanus, and P. shermani). Some of the recognized species within the Plethodon jordani complex show both historical and current-day genetic influence from one or more other species, and mating studies indicate that none of these forms are completely reproductive isolated due to mating barriers (Reagan 1992, Wiens et al. 2006). Where adjoining forms come into contact, they generally tend to hybridize to varying degrees. In addition, certain members of this group also hybridize with members of the Plethodon glutinosus complex (Weisrock et al. 2005, Wiens et al. 2006). Discordance between mtDNA and nuclear data are well-documented (Weisrock and Larson 2006) and reflect various levels of gene-mixing. This not only is occurring today, but likely occurred historically during the Pleistocene as ranges expanded during glacial periods and previously isolated forms came into contact. Here, we recognize all of these species and discuss issues with hybridization in the individual species accounts.
Species Comments:
Identification
Description: Plethodon amplus is a cryptic species within the P. jordani complex. It -- along with P. metcalfi, P. meridianus, and P. montanus -- comprise a group of closely related species that have gray cheeks and are indistinguishable from one another based on external morphology and coloration. The mtDNA haplotypes from these four species do not form monophyletic groups corresponding to each species (Weisrock and Larson 2006), and the structure of mtDNA variation has likely been influenced by gene flow between previously diverged populations. Nonetheless, they continue to be recognized as four closely related species within the P. jordani complex. They are best identified by using either the collection locality, or a combination of collection locality and genetic markers in areas where the forms come into close geographic contact.

All of the gray-cheeked species are dark gray to bluish black above with grayish venters. The tail of adults is slightly longer than the body and is rounded in cross-section. Sexually-active males have conspicuous, rounded mental glands. The adults vary from 8.5-18.5 cm TL and there are usually 16 costal grooves. The gray-cheeked species somewhat resemble melanistic forms of certain Desmognathus species with rounded tails (e.g., D. carolinensis; D. orestes), but differ in head shape, overall size, the size of the back legs relative to the front legs (larger in Desmognathus species), and the absence of a colored line from the eye to the angle of the jaw (usually evident in Desmognathus species).

Plethodon amplus has a very small range and occurs in close geographic proximity to P. metcalfi, P. meridianus and P. montanus. These forms show evidence of past hybridization and mtDNA markers may not be sufficient to confidently identify P. amplus from P. metcalfi or P. meridianus where they occur in close proximity (Heidler 2020, Weisrock and Larson 2006). Additional molecular studies using more refined techniques are needed to determine the composition and distribution of gray-cheeked forms that occur in the general vicinity of P. amplus.
Online Photos:    Google
Observation Methods: Specimens can be observed at night in rock crevices or on the forest floor, and can be found beneath cover objects during the day.
AmphibiaWeb Account
Distribution in North Carolina
Distribution Comments: Plethodon amplus is a very narrow endemic. The known range based on genetic identification extends from southeastern Buncombe County southward through eastern and central Henderson County to western Polk County (Heidler 2020). Heidler (2020) also found populations in western McDowell and Rutherford counties with P. metcalfi mtDNA haplotypes that she suspected were not P. metcalfi and reflected gene capture from past hybridization events. These could potentially also be P. amplus. The status of all of the gray-cheeked populations in this region need more thorough investigation using molecular tools that provide less ambiguous results.
Distribution Reference: Heidler (2020)
County Map: Clicking on a county returns the records for the species in that county.
Key Habitat Requirements
Habitat: This species occurs at lower elevations than most members of the the P. jordani complex. Heidler (2020) found populations at localities that ranged from 475-1200 m in elevation. Most populations were in mature hardwood forests with well-developed leaf litter, although pines were the dominant species at one location. At high elevation sites (>1000 m) within the Hickory Nut Gorge, P. amplus was strongly associated with rock outcrops. At lower elevation sites (<500 m), it was often found less than 6 m from streams. At sites with rich mesic forests, it can be found broadly distributed across the forest floor.
Biotic Relationships: Plethodon amplus often coexists locally with a variety of other woodland and streamside salamanders, including Desmognathus carolinensis and Plethodon yonahlossee. Competitive interactions between these species are poorly resolved and in need of study, but Plethodon amplus and Plethodon yonahlossee common occur together without evidence of strong competitive exclusion of one species by the other.
See also Habitat Account for General Montane Mesic Forests
Life History and Autecology
Breeding and Courtship: Members of the P. jordani complex court from July through early October based on field observations. Tom Ward (pers. comm.) observed courting pairs of P. amplus on 7 September and 28 September in Buncombe Co., which is consistent with the general trend for members of this species complex. Females of the P. jordani complex normally lay a clutch of eggs every other year, and only mate during the years when they nest. Arnold (1976) noted that males will not aggressively court sexually mature females that have small ovarian eggs, but will actively court females with large ovarian eggs.

Arnold (1976) observed courtship of members of the P. jordani complex from four geographic isolates and found them all to be indistinguishable. The following is a summary of the major aspects of breeding and courtship as summarized by Petranka (1998) and that presumably applies to P. amplus as well.

When courting, a male approaches a female and begins nudging, nosing, or tapping her with his snout. He then places his mental gland and nasolabial grooves in contact with the back, sides, or tail of the female and engages in a 'foot dance' in which the limbs are raised and lowered off the substrate one at a time. The male eventually moves forward and presses his mental gland along the side of the female's head and over her nasolabial grooves. The male then turns his head under the female's chin and lifts. Next, the male circles under the female's chin and laterally undulates his tail as he passes. If the female is responsive, she places her chin on his tail and moves forward to the base of the tail. The pair then engages in a tail-straddle walk that may last for 1 hour. During the walk the male may turn and slap the female across her nasolabial region with his mental gland. This introduces pheromones via the nasolabial grooves.

The male eventually stops moving and begins a series of lateral rocking movements of his sacrum. The female begins a series of synchronous lateral head movements counter to the lateral movements of the sacral region of the male. The male then presses his vent to the substratum and deposits a spermatophore. Immediately after, he flexes the tail to one side and leads the female forward. She stops when her vent is over the spermatophore, then lowers her sacrum and picks up the sperm cap. During this process the male arches the sacral region and does a series of pushup motions with the rear limbs. The pair usually splits up and terminates courtship shortly after spermatophore deposition, even if the female is unsuccessful in picking up the spermatophore.
Reproductive Mode: The adults are terrestrial breeders, but the eggs and nests have never been discovered. As with other members of the P. jordani complex, the females presumably nest either in underground retreats or deep within rock crevices during the summer months.
Terrestrial Life History: Virtually all aspects of the terrestrial ecology of this species are undocumented. The juveniles and adults remain beneath cover during the day and actively forage at night during rainy periods or when conditions are moist.
General Ecology
Adverse Environmental Impacts
Status in North Carolina
NHP State Rank: S1
Global Rank: G2
Status in North Carolina: SR
Environmental Threats: This and other eastern salamanders are sensitive to intensive timbering. Local populations of members of the P. jordani complex may decline to near zero following the clearcutting of mature hardwood forests and require several decades to recover (Ash 1988, Petranka et al. 1993, 1994). Less intensive harvesting practices that leave the basic structure of the forest intact would benefit this and other salamander species in southern Appalachian forests. Urbanization and forest fragmentation also poise threats to local populations of this species.
Status Comments: The majority of land within the range of P. amplus is privately owned, with isolated patches of state-owned land (Heidler 2020). Habitat loss and fragmentation from land development is likely the largest threat to P. amplus populations (NC Wildlife Resources Commission 2015). Heidler (2020) found viable populations on three tracts of private land with conservation easements and protected forests. She recommended preserving mature and old growth forests, protect corridors between forested tracts in heavily fragmented areas, and expanding conservation easements where possible among private lands.
Stewardship: This an other Plethodon species lack lungs and use their moist skin as a respiratory organ. They are highly vulnerable to desiccating conditions. Edge effects that results in hotter and drier conditions can be minimized by having large tracts of forested habitats. Mature and old-growth forests that have thick leaf litter, rich organic soils, and closed canopies provide ideal conditions for this and many other salamander species.

Photo Gallery for Plethodon amplus - Blue Ridge Gray-cheeked Salamander

8 photos are shown.

Recorded by: tom ward
Buncombe Co.
Recorded by: tom ward
Buncombe Co.
Recorded by: tom ward
Buncombe Co.
Recorded by: tom ward
Buncombe Co.
Comment: A courting pair that is engaged in a tail-straddle walk. The male is in front and the female is following.
Recorded by: tom ward
Buncombe Co.
Comment: A courting pair in a tail-straddle walk with the male leading.
Recorded by: tom ward
Buncombe Co.
Comment: A courting pair in a tail-straddle walk with the male leading.
Recorded by: tom ward
Buncombe Co.
Recorded by: tom ward
Buncombe Co.