Amphibians of North Carolina

Scientific Name:	Common Name:		Family (Alpha):

NC Records
Plethodontidae Members:
Plethodon metcalfi - Southern Gray-cheeked Salamander

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 metcalfi is a cryptic species within the P. jordani complex. It -- along with Plethodon amplus, P. meridianus and P. montanus -- comprise a group of closely related species that have gray cheeks and are essentially 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 forms are relatively large Plethodon species that 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. Individuals in low-elevation populations of P. metcalfi in Oconee Co., South Carolina -- and in southern Jackson and Macon counties, North Carolina -- have varying levels of brassy or silvery dorsal flecking and in many cases white spotting along the sides (Schwartz 1957a). These were previously describe as a distinct species, P. clemsonae, but molecular data do not support recognizing these forms as a separate species (Weisrock and Larson 2006). The type locality and the most representative populations of 'clemsonae' were eliminated with the construction of Lake Jocassee.

The gray-cheeked species of the P. jordani complex somewhat resemble melanistic forms of certain Desmognathus species with rounded tails (e.g., D. carolinensis; D. ocoee), 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 metcalfi can usually be unambiguously identified by the collection locality. However, It occurs in close geographic proximity to P. amplus and possibly P. meridianus in the eastern portion of its range. All three of these show evidence of past hybridization and mtDNA markers may not be sufficient to confidently identify P. metcalfi in this region (Heidler 2020, Weisrock and Larson 2006). Additional molecular studies are needed to determine the composition and distribution of gray-cheeked forms that occur in the general vicinity of P. amplus. Plethodon metcalfi hybridizes extensively with the Atlantic Coast Slimy Salamander (P. chlorobryonis) in northeastern Georgia (Highton and Peabody 2000). It also contacts the Atlantic Coast Slimy Salamander in northwestern South Carolina where there is a hybrid zone in Anderson and Abbeville counties (Highton and Peabody 2000). In North Carolina P. metcalfi hybridizes with P. jordani on Balsam Mountain and Hyatt Ridge where the Great Smokies meet the Balsam Mountains. A hybrid zone is present where hybrids have reduced amounts of reddish pigmentation on the cheeks (Hairston et al. 1992, Hatfield et al. 2010).

Online Photos: Google iNaturalist

Observation Methods: The adults can be easily observed on summer nights when they feed on the forest floor. They can also be collected during the day beneath logs, stones and other cover objects.

AmphibiaWeb Account

Distribution in North Carolina

Distribution Comments: Plethodon metcalfi occupies the southern Blue Ridge Mountains in North Carolina to as far south as Oconee County, South Carolina where it enters the upper Piedmont. The range includes portions or all of Clay, Macon, Jackson, Transylvania, Henderson, Swain and Haywood counties in North Carolina and Pickens and Oconee Counties in South Carolina. Populations from Polk Co. have been tentatively assigned to this species but need to be confirmed with molecular data. Populations in northern Georgia appear to be hybrids and pure P. metcalfi may not be present there.
County Map: Clicking on a county returns the records for the species in that county.


GBIF Global Distribution

Key Habitat Requirements

Habitat: Plethodon metcalfi can be found in mesic hardwood forests and spruce-fir forests in the Blue Ridge of North Carolina, and in rich woods in the Blue Ridge escarpment and adjoining upper Piedmont of South Carolina where it is often restricted to deep ravines and other cool, shaded habitats. Mature forests with a thick leaf litter layer and abundant coarse woody debris provide optimal habitats. Populations occur above 750 m in elevation, with one exceptional population that was found at 256 m in South Carolina.

See also Habitat Account for General Montane Mesic Forests

Life History and Autecology

Breeding and Courtship: 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). These presumably apply to all seven recognized species in this complex.

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.

The adults of the P. jordani complex appear to court from July through early October based on field observations, with a peak in August and September for P. metcalfi (Hairston, 1983a). A female normally lays a clutch of eggs every other year, and only mates during the year when she 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.

Reproductive Mode: The nests of P. metcalfi have never been found, but gravid females of this and other members of the P. jordani complex move underground in late spring or early summer and presumably oviposit in deep underground recesses. Females appear to oviposit in May in the southern Appalachians based on the presence or absence of gravid females in samples and produce a clutch every other year (Hairston 1983a). Hatching probably occurs in late summer or early autumn about 2-3 months after the eggs are deposited. Females at very low elevation sites in South Carolina may possibly begin laying eggs during the spring months based on the first appearance of juveniles on the ground surface (Schwartz 1957).

Terrestrial Life History: Hairston (1983a) studied several populations in western North Carolina and concluded that the newborns remain beneath ground for 10-12 months after hatching. Small individuals judged to be nearly 1-year old first appeared on the surface in May or June. The males matured sexually about 3 years after hatching when > 43 mm SVL. An estimated 25% of the females oviposited for the first time 4 years after hatching, while another 25% oviposited for the first time one year later. The remaining animals first oviposited 6 years or more after hatching, then every other year for the remainder of their lives. Four females that were dissected by Schwartz (1957) contained from 17-24 mature ova. Based on a regression equation, Hairston (1983a) estimated that female clutch size varied from 11-18 mature eggs per female depending on SVL.

At mid- to higher elevation sites the juveniles and adults are active on the ground surface during the warmer months of the year, typically from mid-May to early October in the western mountains (Petranka 1998). They move underground with the onset of freezing weather in the autumn and remain underground even during warm bouts of weather. At low elevation sites individuals often remain active on the ground surface throughout the winter except during periods of freezing weather (Schwartz 1957). They emerge from burrows or surface cover after dark and forage on the forest floor. Dietary studies are lacking, but the juveniles and adults presumably take a wide array of invertebrate prey as is the case with closely related forms such as P. jordani (Powders and Tietjen 1974).

Nishikawa (1990) found that individuals occupy small, fixed home ranges with little overlap between individuals of the same age or sex. Younger animals were more likely to share their home ranges with adults than with other juveniles. The respective mean size of home ranges for 2-year olds, 3-year olds, adult males, and adult females were 1.52, 2.98, 5.04, and 1.87 m2.

General Ecology

Population Ecology: Populations of members of the P. jordani complex generally tend to be stable through time and likely reflect density-dependent regulation associated with territoriality (Hairston 1983a, 1987, Hairston and Wiley 1993). The adults have small home ranges and will aggressively defend space that contains food or potential mates from intruders (Petranka 1998). This likely sets an upper limit on local population size.

Community Ecology: Hairston (1980a, 1983b) conducted field experiments to examine competitive interactions between members of the P. jordani complex and P. teyahalee, and documented the responses of each species to the experimental removal of the other. Experiments were conducted in the Great Smoky Mountains with P. jordani where the elevational overlap is slight and in the Balsam Mountains with P. metcalfi where the overlap is much more extensive. In both cases the removal of either P. jordani or P. metcalfi increased the surface densities of P. teyahalee. Removal of P. teyahalee did not affect the densities of P. jordani, but did increase the proportion of juveniles in the population. Hairston concluded that competition occurs between the two species, but was unable to pinpoint the resources that were in short supply. Later studies suggest that aggressive interaction related to interference competition for space is the primary factor mediating interactions between these species (Hairston 1987, Petranka 1998).

Adverse Environmental Impacts

Status in North Carolina

NHP State Rank: S5

Global Rank: G4

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 (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. Hairston and Wiley (1993) monitored P. jordani populations in mature forests in western North Carolina and found no evidence of long-term population declines over a 15-year period.

Status Comments: The Southern Gray-cheeked Salamander has a relatively large range compared to the ranges of many member of the P. jordani complex. It is common in most areas of its range and seems secure at present.

Stewardship: Populations are best maintained by having extensive tracts of mature hardwood forests.

Photo Gallery for Plethodon metcalfi - Southern Gray-cheeked Salamander		9 photos are shown.
	Recorded by: B. Bockhahn Macon Co.	Recorded by: B. Bockhahn, J. Thomson Macon Co.
	Recorded by: B. Bockhahn Macon Co.	Recorded by: B. Bockhahn, J. Thomson Macon Co.
	Recorded by: B. Bockhahn Macon Co.	Recorded by: B. Bockhahn Macon Co.
	Recorded by: M. Krintz Transylvania Co.	Recorded by: Owen McConnell Graham Co.
	Recorded by: Owen McConnell & Roger Rittmaster Graham Co.

Plethodon metcalfi - Southern Gray-cheeked Salamander

Photo Gallery for Plethodon metcalfi - Southern Gray-cheeked Salamander

9 photos are shown.