Valdina Farms Salamander
Country distribution from AmphibiaWeb's database: United States
Eurycea troglodytes Baker, 1957
Paul T. Chippindale1
1. Historical versus Current Distribution. Valdina Farms salamanders (Eurycea troglodytes) were described by Baker (1957) from Valdina Farms Sinkhole, Medina County, Texas. Sweet (1978a, 1984) demonstrated that this population includes individuals with a spectrum of morphological features, ranging from highly cave-associated morphologies most similar to those of Comal blind salamanders (E. tridentifera) to surface-like morphologies most similar to those of what he considered Texas salamanders (E. neotenes). He hypothesized that this range of morphologies was the result of hybridization between surface Texas salamanders and a cave-dwelling species, perhaps Comal blind salamanders (note that the known range of Comal blind salamanders is far to the east of the type locality for Valdina Farms salamanders; Sweet suggested that Comal blind salamanders might have a more extensive subterranean range than was recognized). Most recent authors have not recognized E. troglodytes as a distinct species. However, Chippindale et al. (2000) found that salamanders from the Valdina Farms Sinkhole system were phylogenetically nested (based on mitochondrial DNA analysis) within a group of spring and cave populations of Eurycea in the southwestern Edwards Plateau region, where Valdina Farms Sinkhole is located. Combined analyses of allozyme and mitochondrial sequence data support monophyly of this group and reveal deep divergences among many populations. Chippindale (2000) and Chippindale et al. (2000) included all these southwestern populations in the E. troglodytes complex, but noted that additional undescribed species may exist. At present, the E. troglodytes complex encompasses a large and wide-ranging array of spring and cave populations in Bandera, Edwards, Gillespie, western Kerr, Medina, Real, and Uvalde counties. Populations from Val Verde County probably represent the E. troglodytes complex as well, but have not yet been examined for molecular markers. It is likely that salamanders from the E. troglodytes complex occur in Kinney County, but no populations have yet been discovered.
2. Historical versus Current Abundance. Salamanders of the E. troglodytes complex are often abundant at spring outflows, especially in canyons of Bandera, Kerr, and Real counties. It is difficult to assess densities for cave populations. Construction of a diversion dam in the 1980s temporarily submerged Valdina Farms Sinkhole, the type locality of Valdina Farms salamanders, and introduced catfish and other predators. Subsequent surveys (Veni and Associates, 1987; G. Veni, personal communication) have failed to reveal any Valdina Farms salamanders, even in areas of the cave where they once were common.
3. Life History Features.
A. Breeding. Reproduction is aquatic.
i. Breeding migrations. Unlikely to occur.
ii. Breeding habitat. Likely the same as adult habitat.
i. Egg deposition sites. Unknown; closely related species are thought to deposit eggs in gravel substrate.
ii. Clutch size. Unknown.
C. Larvae/Metamorphosis. Most populations in this species complex are paedomorphic, and metamorphosis is unknown for these. However, natural metamorphosis has been observed in populations from several springs in the Sabinal River drainage of Bandera County (Bogart, 1967; Sweet, 1977a). Sweet (1978a) observed a transformed individual in a Uvalde County cave and reported on a transformed individual observed by B.C. Brown in another cave in Uvalde County. Bogart (1967) induced transformation in animals from the type locality through implantation of frog pituitary glands.
D. Juvenile Habitat. Probably the same as adult habitat.
E. Adult Habitat. Individuals in most populations are completely aquatic, but Sweet (1977a, 1978b) found remains of terrestrial invertebrates in stomachs of some transformed individuals that were captured in water; this suggests that transformed animals may venture short distances onto land. Members of the E. troglodytes complex are known only from caves that contain water and the immediate vicinity of spring outflows; individuals in caves are often seen in the open on submerged rock or mud substrate, whereas individuals from spring populations are found under rocks and leaves and in gravel substrate. Water temperature in springs and caves of the Edwards Plateau is relatively constant throughout the year and typically ranges from 18–20 ˚C in the areas inhabited by this species (Sweet, 1982). Sweet (1982) provided a comprehensive distributional analysis of the central Texas Eurycea and discussed hydrogeology of the region in relation to salamander distribution.
F. Home Range Size. Unknown.
G. Territories. Unknown.
H. Aestivation/Avoiding Dessication. Unknown.
I. Seasonal Migrations. Unlikely to occur.
J. Torpor (Hibernation). Probably active throughout the year.
K. Interspecific Associations/Exclusions. As described above, Sweet (1978a, 1984) considered the population at the type locality to be hybrids between E. neotenes and E. tridentifera. Chippindale (1995) and Chippindale et al. (2000) regarded this as unlikely, based on molecular data and geographical considerations, and continued to recognize E. troglodytes as a distinct species.
L. Age/Size at Reproductive Maturity. Sweet (1977a, 1978a) found that in transforming populations (which he considered to be E. neotenes), sexual maturity is concurrent with transformation at 30–32 mm SVL. Bruce (1976) studied Kerr County populations, which almost certainly are part of this species complex (he also considered them E. neotenes). He found that individuals under 25 mm were invariably immature and concluded that males become reproductively active early in their second year, while females mature at the same time but first oviposit at 2 yr of age. Bogart (1967) artificially induced hybridization between Eurycea troglodytes from the type locality and E. tridentifera.
M. Longevity. Unknown.
N. Feeding Behavior. Prey probably consists mainly of small aquatic invertebrates, but no detailed feeding studies of this species have been conducted. Sweet (1977a, 1978a) found remains of terrestrial collembolans and isopods in stomachs of transformed specimens. Transformed individuals maintained on wet moss by Bogart (1967) accepted Drosophila as food.
O. Predators. Unknown.
P. Anti-Predator Mechanisms. Spring-dwellers are secretive.
Q. Diseases. Sweet (1978a,b) found evidence of "red-leg" disease, thought to be caused by bacteria of the genus Aeromonas, in some populations (note that Sweet considered these populations to be E. neotenes).
R. Parasites. Unknown.
4. Conservation. Valdina Farms salamanders were described from Valdina Farms Sinkhole, Medina County, Texas. While it is difficult to assess densities for cave populations, salamanders of the E. troglodytes complex often are abundant at spring outflows, especially in canyons of Bandera, Kerr, and Real counties. Construction of a diversion dam in the 1980s temporarily submerged the type locality of Valdina Farms salamanders and introduced catfish and other predators. Subsequent surveys have failed to reveal any Valdina Farms salamanders, even in areas of the cave where they once were common. This species has not been given special conservation status by either the State of Texas or the Federal Government.
1Paul T. Chippindale
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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Citation: AmphibiaWeb. 2018. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 11 Dec 2018.
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