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Ambystoma bishopi Goin, 1950Reticulated Flatwoods Salamander
Federal Protection: Listed Endangered
State Protection: Endangered
Global Rank: G2
State Rank: S1
Element Locations Tracked in Biotics: Yes
SWAP High Priority Species (SGCN): Yes
Element Occurrences (EOs) in Georgia: 7
Habitat Summary for element in Georgia: Pine flatwoods, moist savannahs, isolated cypress/gum ponds (Mesic longleaf pine-wiregrass flatwoods and savannas)
The reticulated flatwoods salamander has a chocolate-black background with a net-like (“reticulated”) pattern of gray lines on the back, sides, head, and tail. The body is slender relative to other mole salamanders (genus Ambystoma); the head is relatively small, and the tail is quite fat. Adults are typically 12 - 15 cm (4.5 - 6 inches) in total length. The broad-headed, bushy-gilled larva is very distinctive with a prominent tan or beige stripe running the length of the otherwise chocolate-brown body. The larva also has a dark brown stripe through each eye, extending from the nostril to the gills.
Adult reticulated flatwoods salamanders may be confused with the southeastern slimy salamander (Plethodon grobmani) at first glance as the distribution of these two species overlap and adults can be found in the same terrestrial habitats; however, the latter species differs in appearance by having unconnected, widely scattered light spots on the back and sides and a groove between each nostril and the upper lip. Besides having non-overlapping geographic distributions (see the description of its Range below), the reticulated flatwoods salamander can be distinguished from the frosted flatwoods salamander (Ambystoma cingulatum) by slight differences in general appearance and in having a more robust, stout build (lacking a constriction at the neck, and a plumper tail); the frosted flatwoods salamander has a pattern on its underside composed of discrete light spots on a dark background rather than one resembling salt and pepper, and the pattern on its back is lichen-like or “frosted” in appearance rather than the reticulated, net-like pattern of the reticulated flatwoods salamander.
This salamander is endemic to mesic flatwoods habitats within the vanishing longleaf pine-wiregrass community. Slash pine was incorrectly reported in early species accounts as a commonly associated tree species within its non-breeding habitat. Nearly all flatwoods salamander sites currently dominated by slash pine have been converted from historic longleaf pine stands. Pine flatwoods are fire-dependent communities, requiring periodic burns to promote grasses and forbs, while limiting shrubs and hardwoods. Breeding sites are typically shallow, seasonally inundated cypress and/or swamp tupelo ponds or "domes," although flooded borrow pits, roadside ditches, and deep firebreaks are occasionally used. Breeding sites are also dependent on periodic dry season fires, which maintain an open canopy conducive to the luxuriant growth of emergent and submerged grasses, sedges, and forbs necessary for sheltering the aquatic larvae. The reticulated flatwoods salamander in Georgia is confined to the Dougherty Plain (bound by the Pelham Escarpment on the southeast and the Coastal Plains Red Uplands to the northwest) in the southwestern corner of the State; this karst nature of this flat topography (typically characterized by 0-2% slope) is evidenced by the many, actively forming sinkholes that are sites of numerous ponds and marshes. Ephemeral depressional wetlands, occurring throughout this region, that are embedded within a typically open canopied upland pine forest landscape are utilized as breeding ponds by reticulated flatwoods salamanders; these depressions are produced through the gradual dissolution of the underlying limestome and subsidence of the overlaying soil.
Adults are known to eat earthworms, but likely consume other invertebrates as well. Larvae eat a variety of aquatic invertebrates, especially crustaceans such as amphipods and isopods. Captive larvae readily eat small tadpoles and may also do so in the wild.
As adults, flatwoods salamanders are primarily fossorial, living in burrows just below the soil surface. Triggered by rain-laden cold fronts during the fall and early winter breeding season, mature salamanders nocturnally migrate to isolated wetlands en masse. Movements of more than 1.6 km (1 mile) from a breeding site to a terrestrial retreat have been reported. Following mating, female flatwoods salamanders deposit up to 225 eggs singly or in small groups in the dry portions of the pond basin or in grassy areas at the pond margin, usually under leaf litter or logs, at the bases of grass clumps, or at the entrance of crayfish burrows. In most years, repeated rain events eventually fill the wetland and inundate the developing eggs, inducing hatching. However, in some years insufficient rainfall following egg deposition prevents complete inundation, resulting in few eggs hatching and low recruitment. Unlike wetlands that dry completely on a cyclic basis, wetland habitats that have permanent surface water and wetlands associated with surface drainageways usually contain predatory fish. Flatwoods salamander larvae, like larvae of many other amphibian species, need a predatory fish-free environment to survive. Frequent drying of their breeding ponds assures that populations of large predatory fish cannot survive from year to year within these wetlands, even if occasionally introduced during flood events. Larvae are primarily inactive during the day but will emerge from the sheltering vegetation at night to feed. A developmental period of 11 - 18 weeks follows hatching, and larvae typically metamorphose in March or April.
Long-term conservation strategies within Georgia and throughout the distribution of both flatwoods salamander species should not only focus on regular monitoring of known populations (i.e., species presence & abundance and habitat condition), but on locating additional populations through the identification and sampling of suitable habitat through the development of species distribution models and the use of other remote sensing data sources such as LiDAR. Flatwoods salamanders are best surveyed for as larvae, where they can be dip-netted or minnow-trapped from breeding ponds. Aquatic surveys should focus on areas with abundant emergent and submerged plants. Adults are very difficult to find, but are occasionally encountered on rainy fall and winter nights by slowly driving roads that cross between their upland habitat and breeding wetlands. Drift fences equipped with funnel traps and placed adjacent to breeding ponds can intercept migrating adults, but are costly and labor-intensive. Recent research has demonstrated that environmental DNA (eDNA) can detect the presence of flatwoods salamanders and other imperiled pond breeding amphibians even when not detected through traditional physical dip-netting larval surveys.
This species is restricted to the Coastal Plain of Georgia, Florida, and Alabama, but in Georgia, is known to be extant within only a single site. The elusive habits of the flatwoods salamander have posed an impediment to achieving a complete understanding of its geographic distribution and variation. Nearly 85 years following its discovery (1867), based on observed variations in pattern, coloration, and morphology, two forms of the complex were designated as subspecies (1950), one from the Atlantic Coastal Plain (reticulated salamander, A. cingulatum cingulatum) and the other from the Gulf Coastal Plain (frosted salamander, A. cingulatum bishopi). Just 15 years later (1965), these subspecific designations were peremptorily dismissed based largely on conjecture that the reported variations were inconsistent and the distribution of the flatwoods salamander across the Coastal Plain was contiguous permitting gene flow across the range and preventing speciation. Although recent molecular research (2007) has confirmed genetic differences in the subspecies designated nearly 60 years earlier representing divergence sufficient for separate species designation, the observed geographic separation of these two forms by watershed was arbitrarily disregarded; instead a river system was suggested to be a barrier to gene flow, thus separating the respective species, the reticulated flatwoods salamander (A. bishopi) to the west and the frosted flatwoods salamander (A. cingulatum) to the east of the Flint-Apalachicola rivers. This theory however fails to consider the position and distribution of suitable habitat across the landscape and presents one river course as a barrier to movement while ignoring numerous others, many of equal or greater order (e.g., the Escambia, Chicola, Chattahoochee, Altamaha, Savannah, and Edisto rivers, just to name a few). In 2012, molecular researchers using available flatwoods salamander tissue samples from across the Coastal Plain identified two genetically distinctive clades within A. cingulatum, purportedly separated in Georgia and Florida by the Suwannee River yet the lack of significant genetic variation between specimens from South Carolina and those from portions Florida and Georgia suggest that Savannah River has not been a major historical barrier to gene flow. It is unlikely that any river within the Coastal Plain of southeastern North America has been within its current course long enough within the relevant geologic or evolutionary time frame to act as a significant barrier to gene flow. A more likely explanation for the observed genetic divergence within and between species of the flatwoods salamander complex, is that a more permanent landscape feature or features creates such a barrier. The Pelham Escarpment rises as much as 100 feet in elevation, runs from the southwest corner of Georgia for over 100 miles separating the low limestone Dougherty Plain on its eastern flank from Tifton Uplands characterized by well-developed dendritic drainages with narrow and rounded interfluves rising 50 to 200 feet above the narrow valley floors. Such rolling topography does not harbor the typically low sloped flatwoods or the isolated wetlands required as breeding habitat for flatwoods salamanders and thus is a barrier to dispersal and genetic exchange between the two species. Unlike most other rivers of the Coastal Plain, the Apalachicola Basin is positioned within a rift dating to the late Jurassic (~150 million years ago), making this river course a relatively permanent landscape feature. Thus, the reticulated flatwoods salamander (A. bishopi) is restricted to the west of the Pelham Escarpment in Georgia and to the west of the Apalachicola River in Florida, while the distribution of the frosted flatwoods salamander (A. cingulatum) is restricted to the east of Tifton Uplands in Georgia and the east of the Apalachicola River in Florida.
Of the five historical occurrences of the reticulated flatwoods salamander in Georgia, only one is still known to be extant.. Any species with such a reduced range is vulnerable to extinction. Habitat loss has been the primary cause of this salamander's demise throughout its range. Agriculture and silviculture have eliminated the vast majority of the once widespread longleaf pine flatwoods community in Georgia and elsewhere. Because pine flatwoods are typically underlain by semi-hydric soils, forestry practices often involve altering the hydrology by ditching, draining, and/or bedding. These activities are detrimental to both the fossorial and aquatic existence of this species and may interfere with successful migration. Ditching and draining isolated wetlands used by breeding flatwoods salamanders significantly shortens their hydroperiod, halting larval development prior to metamorphosis. Apparent increases in the frequency and duration of changes in rainfall patterns during the last 50 years related to global climate change (i.e., within the southeastern United States, La Niña events resulting in droughts and El Niño events resulting extreme rainfall) coupled with extensive habitat fragmentation across the Coastal Plain have presented the most significant challenge to this species’ continued persistence to date. While shifts in weather and rainfall patterns have certainly occurred over the millennia, historically these changes were attenuated by the resiliency of an unfragmented landscape; in a given area, slight variations in wetland hydroperiod and differences in interconnectedness of wetland features meant that suitable habitat conditions were almost always present somewhere on the landscape for successful breeding, and larval recruitment and survival. The advent of mechanized intensive forestry practices in the 1950s across the Coastal Plain resulted in a dramatic decrease in suitable upland flatwoods habitat; fire suppression on the landscape and exclusion of fire from isolated wetlands, particularly during seasons when wetland basins are typically dry has resulted in increasingly degraded breeding habitats for this species. Consequently, the occurrence of both suitable upland with suitable embedded wetland habitats have become exceptionally rare on the landscape. Extensive efforts to identify suitable habitat in Georgia from 2002 – 2010 were unsuccessful, and during many of these seasons rainfall patterns were not conducive for locating larval within breeding ponds. Even where habitat has been specifically managed through the use of lighting-season prescribed fire and thus maintained in a suitable condition for flatwoods salamanders, a number of prolonged periods of drought within the last 20 years (e.g., 1998-2001) have negatively impacted successful recruitment of young and resulted in the extirpation of some of the last remaining occurrences of this species in Georgia. Perkinsus, a protozoan-like organism known to infect and kill larvae of certain other amphibians, was detected at the one breeding pond on Mayhaw Wildlife Management Area during a particularly wet year. The potential impact of Perkinsus on flatwoods salamanders is unknown. Although not detected in North America, an emerging infectious disease, salamander chytrid fungus (Batrachochytrium salamandrivorans [Bsal]) is of concern for many salamander species world-wide; fortunately, salamanders of the genus Ambystoma are resistant and non-carriers of this often lethal pathogen.
Protected populations occur at, Mayhaw Wildlife Management Area, but apparently have become extirpated from formerly occupied wetlands at the J.W. Jones Ecological Research Center. This species was listed as Threatened under the Endangered Species Act (1999) while it was considered to be the same species as the frosted flatwoods salamander (A. cingulatum); in recognition of the change in taxonomy and in consideration of its conservation status range-wide, the frosted flatwoods salamander was up-listed to Endangered in 2009.
With only one known population of reticulated flatwoods salamander in Georgia, forest management plans of occupied habitats should consider the conservation of this species a top priority. Avoidance of mechanical disturbance to the soil and discontinuing practices which may result in adverse hydrological impacts to breeding sites are critical, especially within at least a 1.6 km (1 mile) radius from the edge of all known breeding wetlands. Periodic lightning-season burns should be prescribed in pinelands inhabited by flatwoods salamanders, and these fires allowed to burn into isolated wetlands. Known breeding sites should be annually monitored.
Federal Register. February 10, 2009. Endangered and threatened wildlife and plants; determination of endangered status for reticulated flatwoods salamander; designation of critical habitat for frosted flatwoods salamander and reticulated flatwoods salamander; final rule. Federal Register 74(26): 6700–6774 [E9–2403].
Goin, C. J. 1950. A study of the salamander, Ambystoma cingulatum, with the description of a new subspecies. Annals of the Carnegie Museum 31(14): 299-321.
Jensen, J. B., and D. J. Stevenson. 2008. Flatwoods salamander Ambystoma cingulatum. Pp. 133-135 in Jensen, J. B., C. D. Camp, J. W. Gibbons, and M. J. Elliott (eds.). Amphibians and Reptiles of Georgia. University of Georgia Press, Athens. 575 pp.
Martof, B. S. 1968. Ambystoma cingulatum. Catalogue of American Amphibians and Reptiles 57.1-57.2.
Martof, B. S. and H. C. Gerhardt. 1965. Observations on the geographic variation in Ambystoma cingulatum. Copeia 1965(3): 342-346.
Means, D. B. 1986. Flatwoods salamander. Pages 42-43 in Mount, R. H., ed. Vertebrate animals of Alabama in need of special attention. Alabama Agricultural Experiment Station, Auburn University, Auburn.
Means, D. B., Palis, J. G., and M. Baggett. 1996. Effects of slash pine silviculture on a population of flatwoods salamander (Ambystoma cingulatum). Conservation Biology 10:426-437.
Palis, J. G. 1996. Element stewardship abstract: flatwoods salamander (Ambystoma cingulatum). Natural Areas Journal 16(1): 49-54.
Palis, J. G. 1997. Breeding migration of Ambystoma cingulatum in Florida. Journal of Herpetology 31:71-78.
Pauley, G. B., O. Piskurek, and H. B. Shaffer. 2007. Phylogeographic concordance in the southeastern United States: the flatwoods salamander, Ambystoma cingulatum, as a test case. Molecular Ecology 16:415-429.
Seyle, W. 1994. Distribution and status of the gopher frog (Rana capito) and flatwoods salamander (Ambystoma cingulatum) in Georgia. Unpublished Report to Fish and Wildlife Service. 18pp.
Stevenson, D. J., and A. E. Davis, Jr. 1995. A summary of rare herpetofaunal species surveys - Fort Stewart Inventory. . The Nature Conservancy Fort Stewart Inventory. Unpublished Report to U.S. Department of Defense.. 21pp.
Vickers, C. R., L. D. Harris, and B. F. Swindel. 1985. Changes in herpetofauna resulting from ditching of cypress ponds in the Coastal Plain flatwoods. Forest Ecology and Management 11: 17-29.
Vitt, L. J. 1981. A survey of the status, distribution and abundance of potentially threatened and endangered vertebrate species in Georgia, Part II: reptiles and amphibians. Unpublished Report to Georgia Department of Natural Resources. 210pp
Whiles, M. R., J. B. Jensen, J. G. Palis, and W. G. Dyer. 2004. Diets of larval flatwoods salamanders, Ambystoma cingulatum, from Florida and South Carolina. Journal of Herpetology 38:208-214.
Thomas M. Floyd and Dirk J. Stevenson
J. Jensen and D. Stevenson, March 2009: original account
T. Floyd, December 2018: account revision