Blue Ridge Two-lined Salamander
© 2013 Todd Pierson (1 of 41)
Country distribution from AmphibiaWeb's database: United States
Eurycea wilderae Dunn, 1920
David M. Sever1
1. Historical versus Current Distribution. Until raised to full species status by Jacobs (1987), Blue Ridge two-lined salamanders (Eurycea wilderae) were considered a subspecies of northern two-lined salamanders (E. bislineata) as described by Dunn (1920). Dunn (1920) stated that the range of his new taxon is the “southern division of the Blue Ridge,” and Dunn (1926) reported that the distribution is “from White Top Mountain, Virginia; south in mountains to Clayton, Rabun County, Georgia, and Cherry Log, Gilmer County, Georgia. They inhabit the whole Southern Blue Ridge region.” The range is sometimes loosely given as “the southern Appalachian Mountains” (Jacobs, 1987; Conant and Collins, 1998), but essentially the range as defined by Dunn (1926) is restricted to the Southern Blue Ridge Mountain physiographic province. Blue Ridge two-lined salamanders occur from base-level streams to the tops of the highest peaks (about 1,900 m). The most remarkable characteristic of this species is the presence of two male morphs that differ dramatically in morphology, especially in regards to the male secondary sexual characters (Sever, 1979, 1999c). One of these is considered the typical “wilderae” morph because it possesses labial cirri, which also characterize males in the type series (Dunn, 1920). This gracile form also possesses a mental gland, seasonally enlarged premaxillary teeth, and 0–2 costal grooves between toes of the adpressed limbs. Males of the other morph, called “morph A” by Sever (1979), lack cirri, mental glands, and seasonally enlarged premaxillary teeth, and they possess 2–3 costal grooves between toes of the adpressed limbs. During the breeding season, the muscles comprising the jaw adductors hypertrophy, making morph A the "big-headed" form in the Southern Blue Ridge. Hypertrophy of the jaw adductors is also known in populations of northern two-lined salamanders and Junaluska salamanders (E. junaluska), but these species all possess mental glands and enlarged premaxillary teeth, and cirri also occur in Junaluska salamanders (Sever, 1979). Females associated with the two male morphs of Blue Ridge two-lined salamanders are indistinguishable but generally have 2–4 costal grooves between adpressed limbs. Morph A has been reported from Blount, Monroe, and Sevier counties, Tennessee, and Graham, Haywood, Macon, and Watuga counties, North Carolina (Sever, 1989), and probably occurs throughout the Southern Blue Ridge. Whether the morphs represent separate species or a polymorphism in Blue Ridge two-lined salamanders still is unresolved, but morph A also occurs in populations in the Piedmont and Coastal Plain of North Carolina within the defined range of southern two-lined salamanders (E. cirrigera; Sever, 1999b). Note that in some other populations of southern two-lined salamanders, such as in northern Alabama and the Cumberland Plateau of southeastern Tennessee, “big-headed” males occur (Mount, 1975; Sever, 1999b), but these individuals possess mental glands and cirri and therefore are not identifiable as morph A. Specimens resembling the male wilderae morph also have been found outside of the Southern Blue Ridge. Individuals morphologically similar to the wilderae morph have been reported by Chermock (1952) from Mount Cheaha in Alabama (which Chermock, as well as Mount, 1975, considers an extension of the Blue Ridge) and by Rossman (1965b) from Wilcox County in the Coastal Plain of Alabama. Allozyme analysis of specimens from these localities, however, align them with Eurycea cirrigera (Jacobs, 1987). I have seen specimens that resemble the male wilderae morph from Cloudland Canyon State Park, Dade County, Georgia, and Kings Mountain State Park, York County, South Carolina. Howell and Switzer (1953) reported “integrades” between E. cirrigera and E. wilderae in the Piedmont of Georgia. An allozyme analysis of the contact zone between E. wilderae and E. cirrigera in northwestern South Carolina revealed the presence of populations of E. wilderae in the Piedmont of Anderson, Oconee, and Pickens counties (Kozak, 1999). The limits of the range of E. wilderae and interactions with E. bislineata and E. cirrigera in areas of contact or sympatry need much more study (Sever, 1999a,b,c). Finally, Jacob’s (1987) group E of Eurycea wilderae included samples from the type locality (Grayson County, Virginia) and two samples from Watuga County, North Carolina, whereas his group F contains all other samples of E. wilderae from more southern areas of the Blue Ridge. Mean D = 0.30 between the E and F groups, far exceeding levels (as low as D > 0.15) commonly used to denote species level differences (Highton, 1998; Thorpe, 1982). Thus, E. wilderae is likely polyspecific; the northern taxon (group E) is referable to E. wilderae, but the southern taxon (group F) requires a new name.
2. Historical versus Current Abundance. Early reports indicate that Blue Ridge two-lined salamanders were frequently encountered during fieldwork. Dunn (1917a) reported on collections of the species near Brevard, Transylvania County, and Linville, Avery County, North Carolina. He stated, “We found the larvae of this species common in every small stream examined, and even in those as large as the Linville River. Adults were found rarely at Brevard. Only 1 adult and 1 transforming specimen were taken near there. At Linville both adults and larvae were common, but adults were found only on land under logs in situations similar to those chosen by various Plethodons and by Desmognathus o. carolinensis (D. carolinensis), in fact often in company with these species.” In Rutherford County, North Carolina, Weller (1930) found Blue Ridge two-lined salamanders to be “very common, both at camp and in the surrounding mountains.” King (1939) stated, “This is one of the common salamanders in the Great Smokies. It may be found in nearly every spring, seep and permanently damp place at suitable elevations.” In another account on Blue Ridge two-lined salamanders in the Smokies, Huheey and Stupka (1967) reported, “This common salamander ranges throughout the Park, occurring at all altitudes.” I have been collecting the species for over 35 yr. I believe that historically the species probably occurred in every rocky mountain stream in the Southern Blue Ridge. Today, Blue Ridge two-lined salamanders are still likely to be found in every stream that has not been damaged by pollution, siltation, deforestation, channeling, and other factors. The species, however, appears rather resilient, and one should not be surprised to find it almost anywhere in the Southern Blue Ridge, even in seemingly inhospitable habitats. For example, Tullulah Creek in Graham County, North Carolina, is historically a clear-flowing rocky, base-level stream. Large samples of Blue Ridge two-lined salamanders could be collected in the 1970s where Tullulah Creek runs through Robbinsville. In the past 15 yr, the stretch through Robbinsville has become increasingly murky and exposed as businesses and homes along the creek have flourished. Other formerly common salamanders, such as three-lined salamanders (E. guttolineata), Junaluska salamanders, and black-bellied salamanders (D. quadramaculatus), are now rare along Tullulah Creek in Robbinsville, but Blue Ridge two-lined salamanders are still common. Adults aggregate at mating/nesting sites from October–April and may be abundant in streams where few adults can be found in mid summer. However, mass metamorphosis of larvae can again make the species seem incredibly abundant along rocky mountain streams in summer, but these individuals are mostly juveniles.
3. Life History Features. Consult Sever (1999a) for additional references on Blue Ridge two-lined salamanders.
A. Breeding. Reproduction is aquatic.
i. Breeding migrations. Many authors have noted that adults can be found considerable distances from water (e.g., King, 1939; Huheey and Stupka, 1967). In mid summer on Wayah Bald, Macon County, North Carolina, I have found dozens under single strips of bark on fallen trees hundreds of meters from the nearest streams. Because the eggs are laid in water and the larvae are aquatic, however, migration must occur to suitable nesting sites. Also, because both males and females migrate, nesting sites constitute mating areas as well. Aggregations start in the fall, and at higher elevations, the mating/nesting areas also serve as hibernation sites. The peak concentration of adults in mating/nesting areas is in spring. Courtship and mating occur on the banks of streams adjacent to nesting areas. The projecting premaxillary teeth of males of the wilderae morph scrape the female’s skin during courtship, allowing secretions of the male’s mental gland to enter the superficial circulation of the female (Arnold, 1977).
ii. Breeding habitat. Usually the eggs are attached to the underside of rocks in flowing water. I have not noticed any consistency in the size of the rock (large or small) or shape (flat or round). Females remain with the eggs. The gelatinous matrix of the eggs is naturally adhesive; eggs may be in one rather discreet cluster or more scattered. A large, favorable rock may have nests of several females. I occasionally have found eggs (with attendant females) by digging through gravelly spring heads; an individual egg in these situations may adhere to several small pieces of gravel.
i. Egg deposition sites. As reported above, nests most frequently have been found under rocks in streams. A considerable amount of variation, however, occurs in the timing of oviposition in this species. Dunn (1920) reported: “At Linville a batch of eggs was found hatching on July 19. They were attached to the under side of a stone in a brook just as are the eggs of bislineata.” Wood (1949) stated that late summer deposition occurs at elevations of 1,525 m, and egg laying occurs earlier at lower elevations. At 1,220 m on Mount Mitchell on 4 May, Wood (1949) found a batch of 87 eggs suspended from the lower surface of a flat stone in a small seepage spring. Bruce (1982a) reported numerous egg clusters in late winter and early spring in streams in the Tuckasegee River basin (695–1,050 m) in Jackson County, North Carolina. At Santeetlah Creek (650 m), Graham County, North Carolina. Bruce (1982b) reported finding nests on 13 and 15 May; at the same site, however, I have found nests in mid March.
ii. Clutch size. The batch of 87 eggs reported by Mitchell from the lower surface of a rock in a small spring on Mount Mitchell probably represents the clutches of > 1 female. Clutch sizes in various populations have been reported to range from 8–34 and 28–56 (Ryan and Bruce, 2000).
C. Larvae/Metamorphosis. Ryan (1997) provides an excellent drawing of the larva. The larvae of Blue Ridge two-lined salamanders are a pale yellow to yellow-green dorsally with a thin, broken dorsolateral stripe, ventral to which is fine mottling and three rows of unpigmented lateral line spots (Eaton, 1956; Ryan, 1997). The tail is flattened and mottled while the venter is clear and a light cream color. Bruce (1986) reported on drift movements of Blue Ridge two-lined salamanders in a stream at 1,170 m in Macon County, North Carolina. He found that downstream movements are dominated by first-year larvae. Upstream movements are not sufficient to compensate for downstream drift, so drift may represent a density-dependent means of population regulation.
i. Length of larval stage. Bruce (1982a, 1985b) reported metamorphosis usually occurs in late spring and early summer after 1–2 yr at a mean 18.5–23.9 mm SVL in stream populations, and at 26.4 mm SVL in a pond. Although a tendency exists for growth rates to be lower at higher elevations, no corresponding tendency occurs for the larval period to be prolonged (Bruce, 1985b). At Santeetlah Creek, Graham County, North Carolina, the larval period typically is 2 yr with mean 31.8 mm SVL in the oldest cohort to metamorphose (Bruce, 1982b). Voss (1993b) found that larvae metamorphose after 1 yr in first-order streams, whereas, in higher-order streams metamorphosis may be delayed for an additional year. This variation is due to warmer temperatures in first order streams (Voss, 1993b). Beachy (1994) found that survival and growth of Blue Ridge two-lined salamander larvae raised in the laboratory together was independent of density, suggesting a lack of competition.
ii. Larval requirements.
a. Food. I am unaware of any study specifically dealing with food habits of larval Blue Ridge two-lined salamanders, although such studies do exist for the sibling species E. bislineata (Smallwood, 1928; Burton, 1976) and E. cirrigera (Petranka, 1984b).
b. Cover. As Petranka (1984b) reported for the sibling species E. cirrigera, larval Blue Ridge two-lined salamanders are found under rock cover during the day and move about stream beds feeding continuously at night (Wiltenmuth, 1997a).
iii. Larval polymorphisms. None are known.
iv. Features of metamorphosis. As reported in "Length of larval stage" above, metamorphosis occurs after 1–2 yr of larval development. Newly metamorphosed juveniles are often abundant around breeding areas in late spring and summer, indicating some synchrony in metamorphosis within a population.
v. Post-metamorphic migrations. Individuals that metamorphose in the late spring or summer may participate in breeding activities the following spring, at the beginning of their third or fourth year (Bruce, 1988b). Thus, the juvenile stage is short, and juveniles may not move far from streamside habitats along the natal area. I have found mature gonads in dissected individuals that are only 25–28 mm SVL, within the range of body sizes characterizing newly metamorphosed animals in some populations (Bruce, 1982a,b, 1985b).
vi. Neoteny. Not known to exist.
D. Juvenile Habitat. As mentioned above, juveniles often are found in streamside habitats. They may be found under rocks and logs, by scraping through leaves and other detritus. Bruce (1986) did not find significant differences between upstream and downstream movements in second-year larvae and metamorphosed individuals.
E. Adult Habitat. Males frequently are found with females under rocks in streams during the spring mating period. Females subsequently stay in the water with their nests, whereas the males move into terrestrial habitats. After eggs hatch, females must follow males into more terrestrial habitats because adults of either sex are usually uncommon along streams in midsummer.
F. Home Range Size. I am unaware of any literature on whether individuals of Blue Ridge two-lined salamanders establish home ranges during any period of the year or stage of life. The study done by Bruce (1986) on upstream and downstream movements suggests that adults and second-year larvae move upstream and downstream in equal frequencies, which no doubt contributes to maintaining a certain density at a locale. First-year larvae, however, move downstream more frequently, resulting in a density dependent mechanism of regulation of excess production (Bruce, 1986).
G. Territories. Wiltenmuth (1997a) reported aggression in larval Blue Ridge two-lined salamanders, but whether this behavior is due to territorial or nonterritorial interference competition requires further investigation.
H. Aestivation/Avoiding Dessication. Not known to occur. Hutchison (1961) reported on critical thermal maxima in a number of salamanders, including three juvenile Blue Ridge two-lined salamanders. He found a CTM of 32.1 ˚C, the lowest of any salamander tested (Hutchison, 1961).
I. Seasonal Migrations. Movements between terrestrial and stream habitats associated with mating/nesting activities were discussed in "Breeding migrations" above.
J. Torpor (Hibernation). Numerous individuals can be found by digging through gravelly spring heads in mid winter, even at high elevations where harsh winter weather surely precludes much surface activity. At lower elevations, however, activity may occur through mid winter.
K. Interspecific Associations/Exclusions. The Southern Blue Ridge physiographic province is a center of salamander diversity in North America (Bruce et al., 2000). The Blue Ridge two-lined salamander commonly is found in association with a dozen or more other species. Brodie (1981) reported that yellow-striped Ocoee salamanders (Desmognathus ocoee; called D. ochrophaeus by Brodie) from several North Carolina localities are mimics of Blue Ridge two-lined salamanders. However, this model-mimic relationship is not as prevalent as in New York between Allegheny Mountain dusky salamanders (D. ochrophaeus) and northern two-lined salamanders (E. bislineata), which are relatively more common in association with Allegheny Mountain dusky salamanders than Blue Ridge two-lined salamanders are with Ocoee salamanders in North Carolina.
L. Age/Size at Reproductive Maturity. The smallest individuals I have dissected that definitely possess mature gonads are 25 mm SVL for a female and 28 mm SVL for a male. However, some individuals as small as 23 mm SVL may be mature, and many are still immature at 30 mm SVL. Bruce (1988b) reported that individuals spend ≥ 1 yr as juveniles after 1–2 yr as larvae. Age at first reproduction in both sexes is estimated to be 3–4 yr, but usually the latter, since most individuals metamorphose at 2 yr (Bruce, 1988b). Mean SVL of adults from various populations ranges from 30.3–49.0 mm (Sever, 1999a), with total lengths of 60–90 mm (Bishop, 1943). The record specimen came from Indian Gap in the Great Smoky Mountains and is 120 mm TL (King, 1939).
M. Longevity. Bruce (1988b) constructed a life table for a population of Blue Ridge two-lined salamanders from 1,100 m in Macon County, North Carolina. He found that R0 = 0.821, indicating a declining population and an unstable age distribution. Bruce believed that this R value was a result of procedural errors and used alternative methods (that do not rely upon any assumptions concerning R) to calculate an estimate mean generation time of 4.4 yr; an annual survivorship of 0.408 was calculated for females. Few animals survive beyond 5 yr and none beyond 10 yr.
N. Feeding Behavior. I am not aware of any studies that specifically address feeding behavior of Blue Ridge two-lined salamanders.
O. Predators. Huheey and Stupka (1967) mention that spring salamanders (Gyrinophilus porphyriticus; see also Bruce, 1979; Beachy, 1994) and common garter snakes (Thamnophis sirtalis) are predators. Larval (Beachy, 1994, 1997) and metamorphosed (Davic, 1991) black-bellied salamanders are known predators, and it is likely that several other larger plethodontids (including red salamanders, Pseudotriton ruber and shovel-nosed salamanders, D. marmoratus) eat Blue Ridge two-lined salamander larvae or adults as well (Bruce, 1982a). Beachy (1994) raised larval Blue Ridge two-lined salamanders in the laboratory for 30 d with larvae of spring salamanders and/or black-bellied salamanders. He found that both predators significantly reduced survivorship of Blue Ridge two-lined salamanders, but that spring salamanders were more effective. Larvae of spring salamanders exposed to high prey densities grew more than those exposed to low prey densities, but prey density had no effect on prey survival. When grouped together with Blue Ridge two-lined salamanders, predator effects on prey survival were additive, indicating neither a mutualistic nor a competitive interaction between spring salamanders and black-bellied salamanders. Beachy (1997a) conducted additional experiments in which he exposed larval Blue Ridge two-lined salamanders to larval black-bellied salamanders. Risk of predation caused significant variation in growth rate, with larvae under highest predation risk growing faster during certain periods. However, larvae metamorphosed at the same time regardless of different growth rates and predation risks. Beachy (1997a) hypothesized that no advantage exists in varying time or size at metamorphosis due to the permanency and low productivity of mountain streams.
P. Anti-Predator Mechanisms. Wiltenmuth (1997a) conducted experiments to determine whether differences in body size among age classes of Blue Ridge two-lined salamander larvae affect intraspecific agonistic behavior, and whether cover availability in the presence of a predator species (larval black-bellied salamanders) affects spacing behavior of larvae. She found that larvae of Blue Ridge two-lined salamanders prefer the vicinity of rock cover and that larger larvae are dominant to smaller larvae. However, Blue Ridge two-lined salamanders did not increase use of rock cover in the presence of visual or chemical cues from black-bellied salamanders. She concluded that either black-bellied salamanders do not pose a substantial threat to Blue Ridge two-lined salamanders or that Blue Ridge two-lined salamanders do not hide under cover to avoid black-bellied salamanders (Wiltenmuth, 1997a).
Q. Diseases. None are known.
R. Parasites. I am not aware of any reports on parasites of Blue Ridge two-lined salamanders.
4. Conservation. There are no current conservation concerns associated with Blue Ridge two-lined salamanders. They are not state or Federally listed (Levell, 1997). Habitat remains plentiful throughout their range, and they remain abundant in suitable streams.
1David M. Sever
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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Citation: AmphibiaWeb. 2019. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 18 Mar 2019.
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