It is perhaps not surprising that the freshwater gastropod fauna of the state is so poorly known.  Although some of the major rivers in the western half of the state have received adequate attention (e.g., Clench & Turner 1956), all the freshwater gastropod surveys conducted in Georgia Atlantic drainages have been limited and local, prior to the present report.

Previous workers in eastern or central Georgia have focused almost entirely on selected prosobranch families - the Viviparidae (Call 1894, Goodrich 1942a, Clench 1962), the Pleuroceridae (Goodrich 1942b, Mihalcik & Thompson 2002), or the Hydrobiidae (Thompson 1969, 1977, Watson 2000).  Goodrich (1939) reported the results of a general survey conducted by Henry van der Schalie on the Ogeechee River, listing Valvata bicarinata, Ferrissia rivularis, Pleurocera (formerly Goniobasis) catenaria, and various species in the genera Campeloma, Amnicola, Somatogyrus, Physa, and Helisoma.  More recently, Sukkestad et al. (2006) have reported seven freshwater gastropod taxa inhabiting the Fort Stewart Army Installation of northern coastal Georgia - Valvata bicarinata, Campeloma decisum, Marstonia halcyon, Pleurocera catenaria, Physa acuta, Helisoma trivolvis, Laevapex fuscus, and Ferrissia sp.

Thompson & Hershler (1991), although focusing primarily on the hydrobioids, offered some general observations on the biogeography of the entire freshwater gastropod fauna of Georgia.  They described an area virtually "devoid of freshwater snails" in the Suwannee, St. Marys, and Satilla Rivers of the state's southern quarter.

Thompson & Hershler also suggested that, with the exception of Lyogyrus latus and the two Viviparus species, the Atlantic drainages of Georgia share no prosobranch species in common with the other major river system of the state, the Chattahoochee/Flint, which drains the western half of the state south to the Gulf.  Dillon & Robinson (2011) have confirmed, however, the occurrence of Pleurocera floridensis in Atlantic drainages around Hawkinsville, a species widespread in the Chattahoochee/Flint and other Gulf drainages south into Florida.  We have also presented evidence that many of the Pleurocera populations formerly believed endemic to Chattahoochee/Flint drainges (e.g. P. albanyensis, P. viennaensis) are P. catenaria, widespread in Atlantic drainages north to Virginia.  Additional faunal similarities may be uncovered as our survey extends west.

In the ecological literature, populations of both Pleurocera catenaria and "Ferrissia sp" (presumably F. fragilis) were involved in a study published by Nelson & Scott (1962) on food web dynamics in the Middle Oconee River.  Krieger and Burbanck (1976) described microhabitat distribution and movement patterns of Pleurocera catenaria (under the alias "Goniobasis suturalis") inhabiting the Yellow River, a tributary of the Ocmulgee. They related environmental features to P. catenaria distribution for purposes of identifying factors limiting local variation in abundance.

The present survey focuses on the gastropod fauna of the Atlantic drainages only.   The gastropod fauna of Tennessee River tributaries draining portions of 7 counties at the northern margin of the state is covered by the FWGTN survey elsewhere on this site.  Our long term plans include an extension of coverage to include tributaries flowing south through Florida and Alabama to the Gulf of Mexico, as resources permit. 

> Methods

The database here analyzed includes 895 records from two primary sources. The largest fraction come from museum collections, primarily the Florida Museum of Natural History in Gainesville (394 records), with smaller contributions from the Georgia Museum of Natural History in Athens, the North Carolina State Museum in Raleigh, the US National Museum, and the Academy of Natural Sciences of Philadelphia.  We queried online databases as available to extract freshwater gastropod records from the 86 Georgia counties draining into the Atlantic, deleted brackish-water records, and inspected the remainder to eliminate any Gulf drainage records from counties on the margins.  We also deleted records collected prior to 1955 or those with no date, as well as duplicate records (usually differing only by date).  We then traveled to the locations of the five museums to verify identifications and examine problematic lots.

The remainder of the records are from our own original collections (231 WKR, 114 RTD), made 2003-21 using simple untimed searches (Dillon 2006).  Ultimately our survey covered approximately 280 discrete sample sites, located throughout the Atlantic drainages of Georgia, in all ecoregions, all subdrainages, and all counties.  A map (in PDF format) showing the distribution of these sites can be downloaded by clicking the figure above.  No “absence stations” are shown.  If freshwater gastropods were not collected at a site, then no record resulted.  Our entire 895 record database is available (as an excel spreadsheet) from the senior author upon request.

The taxonomy employed by the FWGNA project is painstakingly researched, well-reasoned and insightful.  Needless to say, it often differs strikingly from the gastropod taxonomy in common currency among casual users and natural resource agencies.  First-time visitors looking for information about particular species or genera might profitably begin their searches with a check for synonyms in our alphabetical index.
 

> Results

The 41 species and subspecies of freshwater gastropods we have confirmed from the Atlantic drainages of Georgia (plus 2 unconfirmed) are figured in the FWGGA gallery and distinguished on the FWGGA dichotomous key.  Ecological and systematic notes for each species and subspecies are provided on dedicated pages, together with regional distribution maps.  Their distributions and abundances on a continental scale are analyzed in our sections on Biogeography and Synthesis. 

> Acknowledgements

We thank John Robinson and Tom Smith for their help with the field work.  Gracious hosts included John Slapcinsky and Fred Thompson at the Florida Museum of Natural History, Liz McGhee at the Georgia Museum of Natural History, Art Bogan and Jamie Smith at the North Carolina State Museum, Bob Hershler and Jerry Harasewych at the USNM, and Gary Rosenberg, Paul Callomon, and Amanda Lawless at the Academy of Natural Sciences of Philadelphia. The early success of this project in large part depended on the GIS and data analysis skills of Dr. Doug Florian, and continues to depend on the webmastery of Mr. Steve Bleezarde.

> References

Call, R.E. 1894. On the geographic and hypsometric distribution of North American Viviparidae.  Amer. J. Science 48:132-140.   
Clench, W.J. & R.D. Turner. 1956. Freshwater mollusks of Alabama, Georgia, and Florida from the Escambia to the Suwannee River. Bull. Fl. State Mus., Biol. Sci. 1:95-239.   
Clench, W.J. 1962. A catalogue of the Viviparidae of North America with notes on the distribution of Viviparus georgianus Lea. Occas. Pprs. Mollusks 2:261-285. 
Dillon, R.T., Jr. 2006. Freshwater Gastropoda. pp 251 - 259 In The Mollusks, A Guide to their Study, Collection, and Preservation. Sturm, Pearce, & Valdes (eds.) American Malacological Society, Los Angeles & Pittsburgh.Goodrich, C. 1939. Certain mollusks of the Ogeechee River, Georgia. Nautilus 52:129-131. 
Dillon, R. T., Jr. & J. D. Robinson (2011)  The opposite of speciation: Genetic relationships among the Pleurocera populations (Gastropoda: Pleuroceridae) in central Georgia.  Am. Malac. Bull. 29: 1 - 10.
Goodrich, C. 1942a. The American species of Viviparus. Nautilus 55:82-92.   
Goodrich, C. 1942b. The Pleuroceridae of the Atlantic Coastal Plain. Occas. Pprs. Mus. Zool. Univ. Mich. 456:1-6.   
Krieger, K.A. & W.D. Burbanck. 1976. Distribution and dispersal mechanisms of Oxytrema (= Goniobasis) suturalis Haldeman (Gastropoda: Pleuroceridae) in the Yellow River, Georgia, U.S.A. Amer. Midl. Natur. 95:49-63.   
Mihalcik, E. L. & F. G. Thompson 2002.  A taxonomic revision of the freshwater snails referred to as Elimia curvicostata, and related species.  Walkerana 13: 1 - 108.   
Nelson, D.J. & D.C. Scott. 1962. Role of detritus in the productivity of a rock-outcrop community in a piedmont stream. Limnol. Oceanog. 7:396-413.   
Sukkestad, K.E., E.P. Keferl, E.P. & T.D. Bryce. 2006. Freshwater mollusks of Fort Stewart, Georgia, U.S.A. Amer. Malac. Bull. 21:31-38.  
Thompson, F.G. 1969. Some hydrobiid snails from Georgia and Florida. Quarterly J. Fl. Acad. Sci. 32:241-265.   
Thompson, F.G. 1977. The hydrobiid snail genus Marstonia. Bull. Fl. State Mus. 21:113-158.   
Thompson, F.G. & R.H. Hershler. 1991. Two new hydrobiid snails (Amnicolinae) from Florida and Georgia, with a discussion of the biogeography of freshwater gastropods of South Georgia streams. Malac. Rev. 24:55-72.   
Watson, C.  2000.  Results of a survey for selected Hydrobiidae (Gastropoda) in Georgia and Florida.  Proc. First Freshwat. Moll. Conserv. Soc. Sympos. 233 - 244.