Amphibians of North Carolina
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Plethodontidae Members:
NC Records

Plethodon jacksoni - Blacksburg Salamander

Plethodon jacksoniPlethodon jacksoni
Taxonomy
Class: Amphibia Order: Caudata Family: Plethodontidae Subfamily: Plethodontinae Synonym: Plethodon wehrlei
Taxonomic Comments: Populations of a geographically variable species of a large Plethodon with a modal number of 16-17 costal grooves and hind feet that are strongly webbed were traditionally treated as a single species, Plethodon wehrlei. Populations assigned to this form extend from New York to western North Carolina and were known to consist of several unusual geographic variants. Several of these are morphologically distinct and were described as separate species (Felix et al. 2019, Kuchta et al. 2018, Petranka 1998). These include a form associated with two caves in southwestern Virginia that was described as P. dixi (Pope and Fowler 1949), a set of populations from the Ridge and Valley of Virginia that was described as P. jacksoni (Newman 1954), and a form in northeastern West Virginia and adjoining areas of northwestern Virginia that was described as P. punctatus. Another morphologically unique, yellow-spotted variant that occurs in the Cumberland Plateau of West Virginia, Kentucky, and Tennessee was known for years but remained undescribed. Highton (1962a) treated both P. dixi and P. jacksoni as mere geographic variants of Plethodon wehrlei and synonymized them with the later.

Kuchta et al. (2018) analyses mtDNA and nuclear DNA of members of the Plethodon wehrlei complex and found evidence for six major clades. The authors found conflicting patterns depending on the genetic evidence (mtDNA versus nuDNA) and the software programs that were used to analyze the data and define independent lineages. They also noted that all methods of species delimitation come with assumptions that are easily and often violated, thus yielding questionable results. Kuchta et al. (2018) elected to continue recognizing P. punctatus as a valid species, and also resurrected P. dixi as a distinct species. The remaining clades and several unresolved populations were treated as P. wehrlei, which caused this taxon to be paraphyletic. Kuchta et al. (2018) noted that P. wehrlei should not be rejected as a species because it is paraphyletic since this reflects the biological reality of how new species often originate.

Felix et al. (2019) conducted additional genomic studies using a less comprehensive set of data and described the yellow-spotted variant that occurs in the Cumberland Plateau as a separate species, P. pauleyi. They found two poorly resolved and closely related clades that were referred to as 'jacksoni' and 'southern wehrlei' and lumped these together -- along with a poorly resolved population reported by Kuchta et al. (2018) -- to resurrect P. jacksoni as a separate species. As currently constructed by Felix et al. (2019), P. jacksoni includes all the southern populations of the P. wehrlei complex that occupy southwestern Virginia and northwestern North Carolina other than those referable to P. dixi. The authors note that P. jacksoni could potentially be split again pending additional studies of members of this group. The remaining populations that range from West Virginia into Pennsylvania and New York were retained as P. wehrlei (sensu stricto).

Whether one wishes to accept the reasoning and analyses of Kuchta et al. (2018) or Felix et al. (2019) to define species within the Plethodon wehrlei complex is a philosophical choice. Here, we recognize P. jacksoni sensu Felix et al. (2019), with the realization that the taxonomic status of this species is questionable and may change in the future.
Species Comments:
Identification
Description: Plethodon jacksoni is a large, slender Plethodon with hind feet that are strongly webbed. The dorsal ground color is bluish-black and is overlain with moderate to profuse white flecks. Variable numbers of orangish-red spots are also present on the back that can vary from faint to conspicuous. A silvery mottling extends along the back and tail, but is absent or faintly marked on the head (Newman 1954). Moderate to heavy white blotches occur along the lower sides that encroaches upon the belly, which is otherwise deep slaty-blue. The chest and throat regions tend to be mottled with varying amounts of light and dark area, and typically are lighter than the ground color of the belly. Adult males and females that were measured by Newman (1954) from Montgomery Co., Virginia ranged from 69-135 mm (average 116 mm) and 113-133 mm (average 125 mm), respectively. Specimens have 15-18 costal grooves and 3-4 intercostal grooves between the adpressed limbs. Sexually active adult males have a rounded mental gland, swollen tissue around the nasolabial grooves, and a hedonic swelling above the base of the tail.

Geographic variation in this species is poorly documented. The description above is based primarily on Newman's (1954) original description from both cave and surface populations in Montgomery Co., Virginia. Specimens from elsewhere may vary in terms of the degree of development of whitish flecking and spotting, and the presence and amount of reddish pigmentation on the dorsum. This is the only known member of the Plethodon wehrlei complex in North Carolina (sensu Felix et al. 2019), so locality alone should be sufficient for identifying specimens.
Online Photos:    Google   iNaturalist
Observation Methods: Individuals can be found beneath cover objects during the day and on the ground surface at night when conditions are favorable.
AmphibiaWeb Account
Distribution in North Carolina
Distribution Comments: This species is restricted to southwestern Virginia and adjoining areas of northwestern North Carolina. Several reported records from Grandfather Mountain in Avery and Watauga counties appear to be misidentified or mislabeled specimens that are actually P. welleri.
Distribution Reference: Felix et al. (2019)
County Map: Clicking on a county returns the records for the species in that county.
GBIF Global Distribution
Key Habitat Requirements
Habitat: The Blacksburg Salamander has been found in or near caves, in rock crevices, and also on the forest floor where it resides under stones, logs and other surface cover. Newman (1954) described it as showing a preference for the drier upper third of hillsides where other congeners were absent. North Carolina populations are generally associated with mesic hardwood forests and forested slopes, and often where there are rocky ledges or forest-floor habitats with numerous logs and flat rocks.
See also Habitat Account for General Montane Mesic Forests
Life History and Autecology
Breeding and Courtship: The breeding season and courtship behavior of this member of the P. wehrlei complex are undocumented.
Reproductive Mode: Females presumably oviposit in deep underground cavities since eggs of this and other members of the P. wehrlei complex have never been found on the ground surface.
Terrestrial Life History: Almost all aspects of the terrestrial life history of this species are undocumented. Individuals are generally active on the ground surface from April through October.
General Ecology
Adverse Environmental Impacts
Status in North Carolina
NHP State Rank: S2
Global Rank: GNR
Status in North Carolina: T

Photo Gallery for Plethodon jacksoni - Blacksburg Salamander

2 photos are shown.

Plethodon jacksoniRecorded by: E. Corey, B. Roach, M. Amadon, L. Hicks
Alleghany Co.		Plethodon jacksoniRecorded by: E. Corey and L. Williams (NCWRC)
Stokes Co.