Amphibians of North Carolina

Scientific Name:	Common Name:		Family (Alpha):

Plethodontidae Members:
Eurycea wilderae - Blue Ridge Two-lined Salamander

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Taxonomy

Class: Amphibia

Order: Caudata

Family: Plethodontidae

Subfamily: Spelerpinae


Taxonomic Comments: Eurycea wilderae is a member of the Eurycea bislineata species complex, which includes a group of stream-breeding salamanders that are found in eastern North America, many of which are referred to as two-lined salamanders. One wide-ranging member, Eurycea bislineata, was traditionally treated as a polytypic species that contained three subspecies (E. b. bislineata; E. b. wilderae; E. b. cirrigera). Jacobs (1987) conducted a broadscale survey of allozyme patterns of populations across the eastern US and found several genetically differentiated groups. He recommended that the subspecies of E. bislineata be raised to the species level based on genetic distances between groups. Subsequent studies of contact zones support recognizing these as full species, with E. wilderae being a lineage that is mostly restricted to the southern Appalachian Mountains. Kozak et al. (2006) conducted a mtDNA analysis of populations of the Eurycea bislineata species complex across the eastern US. They were able to delineate 13 major phylogenetically and geographically distinct lineages that were associated with pre-Pleistocene drainage patterns in eastern North America. Populations currently recognized as E. wilderae consist of three genetic groups and frequently contain haplotypes of E. cirrigera, suggesting that hybridization has occurred between these forms one or more times during their evolutionary history. Data from Kozak et al. (2006) and Jacob (1987) indicate that both E. wilderae and E. cirrigera are polyphyletic lineages, and that the recognition of additional species may be warranted in the future. The recent description of the Carolina Sandhills Salamander (E. arenicola) is the first of what will likely be several new species that are described from populations that are currently recognized as either E. wilderae or E. cirrigera. Stuart et al. (2020) provide a comprehensive review of the systematics of the Eurycea bislineata species complex.
Species Comments:

Identification

Description: Eurycea wilderae is a small, slender plethodontid that has a broad, greenish yellow to bright orangish dorsum that is bordered on either side by a thinner, dark brown or black stripe that extends onto the tail. The stripe begins immediately behind the eye and typically extends beyond the rear legs and onto the tail before breaking up into a linear series of spots. Specimens are occasionally encountered with stripes that begin to break up before reaching the hind legs, or with stripes that terminate immediately before reaching the tail. The dorsum usually contains numerous, scattered black spots or blotches and the venter is yellowish. The sides of the body can have varying degrees of scattered black spots or blotches, but specimens frequently lack these altogether. The elongated tail is laterally compressed and constitutes about 55-60% of the total length (Sever 1999).

Average adult size is similar between the sexes, and local populations often vary substantially in average size. The mean SVL and TL of adults in a series of samples from throughout the range varied from 30-49 mm and 60-90 mm, respectively (Sever 1999). The record TL for an individual is 12.1 cm. The number of costal grooves varies from 13-16 and tends to increase with elevation. Sever (1999) noted that populations below 1600 m have a modal number of 14 costal grooves versus 15 for populations above 1600 m. Sexually-active males develop elongated cirri, swollen, fan-shaped mental glands, and elongated, unicuspid, premaxillary teeth. The teeth often pierce the male's lip and are used to abrade the female's skin and introduce mental gland secretions into the female's circulatory system during courtship. The cirri and mental glands are less evident during other times of the year, and the teeth are shed after breeding and replaced with smaller, bicuspid teeth (Petranka 1998, Sever 1999). In certain populations, sexually active males have been found that lack all of the secondary sexual characters described above, and instead have hypertrophied jaw musculature. These 'Morph A' phenotypes typically co-occur with typical males and have been shown to be conspecific morphs that are associated with alternative reproductive tactics (Pierson et al. 2019).

Hatchlings average 7-9 mm SVL and 11- 14 mm TL (Petranka 1998). The larvae are dusky colored above with 6-9 pairs of light dorsolateral spots on the body. The body is streamlined and the tail fin stops near the insertion of the rear limbs. The venter is light colored with numerous iridophores. Hatchlings and young larvae superficially resemble Desmognathus larvae but have reddish gills with longer and more slender rami, and squared rather than rounded snouts.

At lower elevation sites along the Blue Ridge Escarpment where E. cirrigera and E. wilderae meet, both species have 14 costal grooves and the adults of these two species are largely indistinguishable. The extent to which the black stripes extend onto the tail varies markedly in both species, and it is not a diagnostic trait (Sever 1999a). However, the general tendency for the stripe to continue farther towards the tail tip in E. cirrigera works as a general rule.

Online Photos: Google iNaturalist

Observation Methods: The larvae are most easily found by searching small pools in headwater streams, or by using kick nets in larger streams. The terrestrial juveniles and adults can be found beneath cover objects during the day or by searching the forest floor at night where they forage in the open.

AmphibiaWeb Account

Distribution in North Carolina

Distribution Comments: As the name implies, the Blue Ridge Two-Lined Salamander is found mostly in the southern Appalachian Mountains. The range extends from White Top Mountain in southwestern Virginia through western North Carolina and eastern Tennessee. It terminates in northern Georgia and northwestern South Carolina, where populations have been found into the upper Piedmont. In North Carolina populations are mostly restricted to the Blue Ridge Mountains, with a few records from the extreme western Piedmont that appear to be this species.
Distribution Reference: Sever (1999)
County Map: Clicking on a county returns the records for the species in that county.


GBIF Global Distribution

Key Habitat Requirements

Habitat: The adults breed in running water and use habitats that range from small fish-free headwater streams to intermediate-sized streams that support predatory fish. Headwater streams and other small streams are particularly important habitats for this species. The juveniles and adults live beneath rocks, logs, and other cover along the margins of streams or seeps, but also use forest floor habitats far from running water during the warmer months of the year. Petranka and Smith (2005) surveyed forest habitats within the first 40 meters of the stream edge and found the adults to be rather evenly distributed with respect to distance from the streams. Crawford and Semlitsch (2007) searched within the first 100 meters of stream margins and found that most adults were within 70 meters of the streams. Females can be found beneath submerged rocks and debris in streams where they oviposit and guard their eggs, and both sexes tend to concentrate in and near the streams during the winter months. In many respects, the habitat requirements parallel those of Ambystoma species in requiring both an aquatic breeding site and a large adjoining forest buffer that is used for feeding and shelter.

Biotic Relationships: The larvae coexist with crayfishes, fishes, and larger salamanders and are likely preyed upon by these predators. Beachy (1993) conducted a field experiment and found that E. wilderae larvae are vulnerable to predation by large Desmognthus amphileucus larvae. In a related experiment, Beachy (1994) found that growth and survival of Eurycea in stream enclosures were independent of larval density, although Eurycea had lower survival in the presence of both predatory Gyrinophilus porphyriticus and D. amphileucus larvae. Of the two predators compared, Gyrinophilus was the more effective predator. Bruce (1979) found that larval G. porphyriticus ate both adult and larval Eurycea wilderae. The juveniles and adults are taken by Eastern Screech Owls and undoubtedly by many other predators that frequent streamside woodland communities such as shrews, raccoons, and woodland birds.

See also Habitat Account for Montane Mesic Forests with Seepages/Headwater Streams

Life History and Autecology

Breeding and Courtship: Males and females court on the forest floor and engage in a stereotypic tail-straddle walk that is typical of plethodontid salamanders (Kozak 2003). After approaching a female, the male and female often stand side-by-side, then raise their heads, arch their dorsums, and touch cheeks. Both sexes then simultaneously rub cheeks in a circular motion. The male next engages in a persuasion phase where he moves his chin in lateral and circular motions over the female's head, dorsum, and tail. The male may later place his head on the dorsum of the female and pull his head back either slowly in one or several short strokes, or rapidly in a snapping motion. This causes the elongated teeth of the male to scratch the skin of the female and introduces pheromones from the mental gland. The pair eventually engages in a tail-straddle walk in which the female places her head on the male's tail and is led forward. The male deposits a spermatophore, then moves his tail to the side of his body while arching it at a 90 degree angle above his body. The female responds by moving forward and inserting the spermatophore into her cloaca.

Reproductive Mode: Many females appear to mate on land during the autumn, and perhaps during the early spring months. They store sperm in their cloacas until they oviposit during the winter or spring months. The cream-colored to whitish eggs are attached to the undersides of stones, rocks, and occasionally submerged logs. In many cases females nest in submerged cavities on the undersides of rocks that are embedded in the stream bottom. When ovipositing, a female flips on her back and arches the tail and back in order to make cloacal contact with the substrate. She then attaches eggs singly to the undersides of a submerged rock or other substrate in a tight monolayer (Petranka 1998). Each egg is suspended by a short broad stalk to a support structure. With time, the stalk and egg membranes become flimsy and the eggs dangle freely in the water. Bruce (1988b) found an average of 41 mature ova (range = 28-56) in females that he examine from a population in western North Carolina, and clutch size was positively correlated with female SVL.

Females often remain with their eggs through hatching and probably defend them from predators such as small crayfishes and invertebrates. Eggs in early to intermediate developmental stages have been found in western North Carolina from February to May (Bruce 1982a, 1988b, Sever 1983b), and in eastern Tennessee in April (King 1939). The incubation period lasts 4-10 weeks depending on local stream temperatures. Hatching occurs from May-August in western North Carolina (Bruce 1982a, b, 1985b).

Aquatic Life History: The embryos hatch with conspicuous yolk reserves and probably do not begin feeding until most of the yolk is resorbed. The larvae live in slow-moving pools or near stream margins, but can also be found in riffles and runs, particularly when drifting. They are primarily benthic feeders and prowl slowly about the stream bottom or over rocks in search of small prey. The larvae mostly feed on small aquatic invertebrates such as copepods, cladocerans, midge larvae, stoneflies, caddisflies, and mayflies, but also occasionally consumes terrestrial invertebrates such as mites and oligochaetes that fall or wash into streams (Bumpers et al. 2017, Johnson and Wallace 2005, Trice et al. 2015).

Although the larvae are primarily benthic-dwellers, they often drift downstream. Bruce (1986) found that first year larvae are more likely to move downstream than upstream, and that small larvae drift downstream disproportionately more than large larvae and adults. In contrast, upstream and downstream movements of older larvae and adults are about equal. It is uncertain if drift is active or passive; however, it appears to be an important dispersal mechanism that increases gene flow between local populations.

Bruce (1982a, b, 1985b) found that length of the larval period, growth rates, and size at metamorphosis are highly variable in populations of E. wilderae in the southern Appalachians. The larval period lasted 1-2 years, but in any population either a 1-year or 2-year larval period predominated. Overall, there was little correspondence between growth rates and length of larval period among populations. Average size at metamorphosis varied from 18-19 mm SVL in 1-year old larvae at one site (Bruce 1982a) to 32 mm SVL in 2-year old larvae from a second site (Bruce 1982b). Metamorphosis occurred from April-July, but in any given population was restricted to a 2- or 3-month period.

Eurycea wilderae in first order streams in the southern Appalachians tend to have larval periods of about 1 year, while those in downstream sections of the same drainages have mixed larval periods of about 1 or 2 years, depending on whether the larvae overwinter (Voss 1993b). In this study the mean size of metamorphs tended to decrease seasonally from May through August and the metamorphs averaged 18-25 mm SVL. Differences in length of the larval period likely reflect the fact that first order stream are warmer during the growing season. Beachy (2018) found that larvae that were fed more food grew faster, but did not metamorphose significantly sooner. In contrast, larvae grown at a high temperature metamorphosed an average of 55 days earlier that those grown at a low temperature. The weak response in timing of metamorphosis to variation in food is consistent with findings for other plethodontid salamanders.

Terrestrial Life History: The juveniles and adults live both in stream and streamside habitats, as well as on the forest floor. Individuals show a tendency to concentrate in or near streams during the winter months, but disperse widely into the surrounding forest during the warmer months of the year (Crawford and Semlitsch 2007, Petranka and Smith 2005). During the warmer months of the year the juveniles and adults emerge at night and forage for small invertebrates on the forest floor or along streambanks. Petranka and Murray (2001) estimated the terrestrial density in a mesic cove forest to be 1,491 individuals per hectare in plots that extended 30 m from a stream in western North Carolina. In his studies in western North Carolina, Bruce (1988b) found that juvenile E. wilderae that transformed after 1-2 years become sexually mature after 3-4 years. The juvenile stage lasted about 2 years and the mean generation time was 4.4 years.

General Ecology

Adverse Environmental Impacts

Status in North Carolina

NHP State Rank: S5

Global Rank: G5

Environmental Threats: The Blue Ridge Two-lined Salamander is a relatively common species and is in minimal need of protection. Like many other salamanders, this species is sensitive to timbering, land clearing, stream pollution and stream siltation and is often absent from urban areas or highly disturbed landscapes. This species is most common in small, shaded streams that tend to be detritus-based food webs. Johnson and Wallace (2005) found that both the density of larvae and their growth rates declined significantly after leaf litter was experimentally prevented from entering a stream stretch. This emphasizes the importance of having a forested buffer to support both the adult and larval populations.

Photo Gallery for Eurycea wilderae - Blue Ridge Two-lined Salamander		33 photos are available. Only the most recent 30 are shown.
	Recorded by: A. Burgos-Melendez Avery Co.	Recorded by: Andrew W. Jones Polk Co.
	Recorded by: Andrew W. Jones Polk Co.	Recorded by: B. Bockhahn United States Co.
	Recorded by: K. Bischof Transylvania Co.	Recorded by: B. Bockhahn, J. Thomson Buncombe Co.
	Recorded by: Pete Dixon Madison Co.	Recorded by: K. Bischof Transylvania Co.
	Recorded by: K. Bischof Transylvania Co.	Recorded by: Owen McConnell Graham Co.
	Recorded by: K. Bischof, E. Corey Transylvania Co.	Recorded by: tom ward Buncombe Co.
	Recorded by: tom ward Buncombe Co.	Recorded by: tom ward Buncombe Co.
	Recorded by: tom ward Buncombe Co.	Recorded by: tom ward Buncombe Co.
	Recorded by: Steve Hall and Bo Sullivan Ashe Co.	Recorded by: tom ward Buncombe Co. Comment: A view of the prominent cirri that develop on males during the breeding season.
	Recorded by: tom ward Buncombe Co.	Recorded by: tom ward Buncombe Co.
	Recorded by: tom ward Buncombe Co.	Recorded by: J. Zimmardi Burke Co.
	Recorded by: Owen McConnell Graham Co.	Recorded by: Owen McConnell Graham Co.
	Recorded by: T. Nergart Transylvania Co.	Recorded by: K. Safley Watauga Co.
	Recorded by: A. Wallace Rutherford Co.	Recorded by: Jim Petranka Macon Co. Comment: A view of the prominent cirri that develop on males during the breeding season.
	Recorded by: Steve Hall, Haven Wiley, Dee Stuckey, UNC Vertebrate Field Biology Class Swain Co.	Recorded by: Steve Hall, Haven Wiley, Dee Stuckey, UNC Vertebrate Field Biology Class Swain Co.

Eurycea wilderae - Blue Ridge Two-lined Salamander

Photo Gallery for Eurycea wilderae - Blue Ridge Two-lined Salamander

33 photos are available. Only the most recent 30 are shown.