Jollyville Plateau Salamander, Tonkawa Springs Salamander
© 2013 Nathan Bendik (1 of 2)
Eurycea tonkawae Chippindale, Price, Wiens and Hillis, 2000
Paul T. Chippindale1
1. Historical versus Current Distribution. Jollyville Plateau salamanders (Eurycea tonkawae) were described by Chippindale, Price, Wiens, and Hillis (2000); the type locality is a spring at the margin of the Jollyville Plateau in the city of Austin, Travis County, Texas. Other spring populations of this species are known from the Jollyville Plateau and Brushy Creek areas of Travis and Williamson counties (Chippindale et al., 2000; Davis et al., 2001). Chippindale et al. (2000) provisionally considered populations from several caves in the area, including the recently discovered Buttercup Creek Cave system in the Cedar Park area of Williamson County, to represent this species. However, they emphasized that some of these cave forms may prove to be distinct species. Most of the known populations were discovered recently; the few populations known prior to the work of Chippindale (1995) and Chippindale et al. (2000) had been considered peripheral isolates of E. neotenes (Baker, 1961; B.C. Brown, 1967a,c; Sweet, 1978a, 1982). Eurycea tonkawae is a member of the "northern group" of Chippindale (1995, 2000) and Chippindale et al. (2000); this monophyletic group occurs northeast of the Colorado River in the Edwards Plateau region of central Texas. Based on molecular markers, this and other northern species are extremely divergent from E. neotenes and other Eurycea from the southern Edwards Plateau region (Chippindale et al., 2000).
2. Historical versus Current Abundance. Little is known of the historical abundance of this species. Individuals may be common at some spring outflows. Krienke Spring, a site in the Brushy Creek drainage of Williamson County from which a large series was collected (preserved at the Texas Memorial Museum, Austin, Texas), apparently was destroyed by quarrying operations in the 1960s (Sweet, 1978a). An office building recently was built directly above the one other known Brushy Creek locality (Chippindale et al., 2000). A morphologically unusual cave population on the Jollyville Plateau, which may represent this species (Salamander Cave; Sweet, 1978a), now lies beneath an apartment complex (J. Reddell, personal communication). Chippindale et al. (2000) briefly addressed some aspects of the conservation biology of this species; Price et al. (1995) provided a more detailed discussion. Currently, the City of Austin is conducting comprehensive studies of spring populations in the Jollyville Plateau region and formulating policies for protection of this species (Davis et al., 2001; unpublished data). This work involves detailed analyses of habitat and water quality parameters and their relationship to salamander distribution and abundance. Preliminary results indicate an inverse correlation between the degree of urbanization and salamander abundance at spring outflows.
3. Life History Features.
A. Breeding. Reproduction is aquatic.
i. Breeding migrations. Unlikely to occur.
ii. Breeding habitat. Unknown; a subset of the adult habitat.
i. Egg deposition sites. Unknown; some other spring-dwelling species of central Texas Eurycea are thought to deposit eggs in gravel substrate. The highest ratios of small juveniles to large juveniles and adults have been observed in March–August (City of Austin, 2000).
ii. Clutch size. Unknown.
C. Larvae/Metamorphosis. This species is paedomorphic, and natural metamorphosis is unknown.
D. Juvenile Habitat. City of Austin personnel found that juveniles are more likely than adults to occur in shallow water near stream edges; they appear to prefer substrates with smaller particles than do large juveniles or adults (Davis et al., 2001).
E. Adult Habitat. Completely aquatic. Jollyville Plateau salamanders are known only from the vicinity of spring outflows, under rocks and leaves, and in gravel substrate. City of Austin personnel have found a positive correlation between abundance of large juvenile and adult salamanders and area of cobble available (Davis et al., 2001). Individuals in spring populations of the Jollyville Plateau region were found behaving (apparently) normally at water temperatures that ranged from 10.6–30.0 ˚C, and no correlation was found between water temperature and salamander abundance (Davis et al., 2001). Preliminary results indicate that salamander abundance decreases as the degree of urbanization increases (Davis et al., 2001). Nitrate levels are a particular concern; during a 2-yr study, the highest observed incidences of dead individuals and animals with spinal deformities occurred at one site (the type locality) for which nitrate levels were particularly high (Davis et al., 2001). 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. However, available evidence suggests that this species makes extensive use of subterranean aquatic habitat, especially when surface spring flows decrease (Davis et al., 2001). On several occasions, City of Austin personnel found apparently healthy adult salamanders with the return of spring flow at sites that had been dry for months.
I. Seasonal Migrations. Unlikely to occur, although there may be seasonal variation in surface versus subsurface habitat use (Davis et al., 2001).
J. Torpor (Hibernation). Animals are probably active throughout the year.
K. Interspecific Associations/Exclusions. Other species of salamanders are not known from the habitat of this species.
L. Age/Size at Reproductive Maturity. Unknown. Average length of specimens measured by Chippindale et al. (2000) was 30.5 mm SVL; all measured were thought to be sexually mature, but this was only verified for some of the specimens.
M. Longevity. Unknown.
N. Feeding Behavior. Prey probably consist mainly of small aquatic invertebrates, but no detailed studies of feeding in this species have been conducted. City of Austin personnel analyzed gut contents of individuals that were found dead and found a wide range of invertebrate prey items representative of the diversity found in salamander habitats (Davis et al., 2001). Particularly common prey items included chironomid larvae, physid snails, copepods, and ostracods.
O. Predators. Circumstantial evidence suggests that centrarchid fishes may substantially reduce numbers of salamanders at some sites (Davis et al., 2001).
P. Anti-Predator Mechanisms. Secretive.
Q. Diseases. Unknown.
R. Parasites. Analyses of specimens found dead revealed encysted metazoan parasites (species unknown) in ova, pancreas, gut, and skeletal muscle. One individual had nematode parasites in the intestine (Davis et al., 2001).
4. Conservation. Because Jollyville Plateau salamanders were described only recently and most of the known populations were discovered recently, little is known of the historical abundance of this species. Individuals may be common at some spring outflows, although development is known to have affected some populations and may be affecting others. Currently, the City of Austin is conducting comprehensive studies of spring populations in the Jollyville Plateau region and formulating policies for protection of this species. This work involves detailed analyses of habitat and water-quality parameters and their relationship to salamander distribution and abundance. Not surprisingly, preliminary results indicate an inverse correlation between the degree of urbanization and salamander abundance at spring outflows.
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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