Although perhaps not as environmentally heterogeneous as neighboring states, South Carolina does include some land form diversity. The state has traditionally been divided into three physiographic provinces, corresponding closely with US Forest Service “Ecoregions” as well as with USDA plant hardiness zones. The (rather low) fall line runs diagonally across the middle of the state, from Cheraw in the northeast, through the capital city of Columbia, to Augusta (GA) in the southwest. Thus the state may be divided into its Atlantic Coastal Plain Province in the southeast and its Piedmont Province through most of the northwest. The three most northwestern counties of the state contact a third physiographic province, the Blue Ridge. 

In South Carolina the Blue Ridge Province is equivalent to the “Central Appalachian Broadleaf Forest” ecoregion, and to USDA plant hardiness zone 7a (average annual minimum temperature 0 – 5 degrees C). The Piedmont is equivalent to the “Southeastern Mixed Forest” ecoregion, or USDA zone 7b (5 – 10 degrees C ). The Coastal Plain is equivalent to the “Outer Coastal Plain Mixed Forest” ecoregion and primarily zone 8a (10 – 15 degrees C.) There is a small strip of USDA plant hardiness zone 8b (average annual minimum temperature 15 – 20 degrees C) along the southern coast.

The surface geology of South Carolina is almost entirely sedimentary and quite sandy, with small regions of Paleozoic granite in the extreme northwest. There are three major river systems, all of which originate in the mountains of western North Carolina and flow southeast to the Atlantic: the Pee Dee, the Broad/Catawba/Santee, and the Savannah. The state also contains several smaller coastal plain drainages: the Black, the Ashley/Cooper, the Ashepoo/Combahee/Edisto and the Coosawhatchie.

The state was deforested by timber interests beginning in the early eighteenth century, and intensive row crop agriculture through the ensuing 200 years led to severe erosion. Although today’s land use practices are much improved, most South Carolina rivers now carry heavy burdens of sediment, and solid substrate is rare (Harding et al. 1998). The first half of the twentieth century saw most of the major rivers impounded for hydroelectric power. The “Santee-Cooper Project” created Lakes Marion and Moultrie, diverting most of the flow of the Santee River down the (previously minor) Cooper River into Charleston Harbor. Other large impoundments in the Santee system include Lakes Greenwood and Murray on the Saluda River west of Columbia and Lake Wateree north of Columbia. The Savannah River was dammed at four points upstream from Augusta, creating a series of lakes from its headwaters to the fall line. Although the Pee Dee River has escaped impoundment in South Carolina, several large dams in North Carolina have doubtless impacted its habitat quality.

Like most of the United States, at no time in its history has South Carolina seen a comprehensive survey of its freshwater gastropods.  The state’s molluscan fauna was first catalogued by Gibbes (1848) and then by Mazyck (1913), the latter contributing his own scattered observations (primarily from the Charleston area) to a thorough survey of the literature. Mazyck compiled a list of 43 freshwater gastropod species, citing an example locality if one was known to him or a published reference if he himself had made no confirming collection. Subsequent taxonomic revisions would reduce Mazyck’s list to 23 species by synonymy, plus four dubious entires.  

The freshwater environment of South Carolina has unquestionably seen tremendous change since Mazyck’s 1913 catalogue. Meanwhile, modern improvements in transportation have made comprehensive field surveys of large scope feasible, and modern methods of information processing have made data retrieval convenient. The purpose of this web site, and indeed of the larger FWGNA project, is to document the freshwater gastropod fauna of South Carolina as it inhabits the rivers, streams, and ponds of The Palmetto State today, for no other reason than the love of science. 

> Methods

Recently the US Environmental Protection Agency has coordinated a joint effort involving the USGS, the US Forest Service, state natural resource agencies, and conservation groups aimed at producing a uniform system of ecoregions.  This system features four tiers.  At Level I, the entire state of South Carolina is classified as "Eastern Temperate Forest."  The three Level II ecoregions recognized in South Carolina correspond to the the USFS ecoregions outlined in the introduction above.  At Level III, the federal system recognizes five ecoregions in this state: Blue Ridge, Piedmont, Southeastern Plains, Middle Atlantic Coastal Plain, and Southern Coastal Plain.

The FWGSC database as of October 2023 comprises 1,989 records. A nucleus of 104 records dates from 1988, when RTD was awarded a small grant by the SC Heritage Trust to survey the state for Pleurocera (formerly Goniobasis) catenaria (Dillon 1988). He visited 233 sites in connection with the work, which were combined with data from 447 sites visited by E. P. Keferl and ultimately published in the proceedings of the Freshwater Mollusk Conservation Society (Dillon & Keferl 2000). Although only 44 of these sites were positive for pleurocerids, the opportunity presented itself to collect freshwater gastropods of all species, and the present survey was born.

Major long-term contributions to this effort have been made by Mr. Jim Glover, Mr. David Eargle, and Mr. Justin Lewandowski of the South Carolina Department of Health and Environmental Control.  SC-DHEC personnel annually take semi-quantitative macrobenthos samples at hundreds of sites throughout the state in connection with their water quality monitoring responsibilities.  RTD was given access to sorted voucher-type freshwater gastropod collections dating back into the 1970s, entire (unsorted) macrobenthos samples taken 1989 – 1994, and extensive records and collections taken thereafter, from which have been extracted 771 freshwater gastropod records.

Our colleague Will Reeves made available to us the Entomology Collection at Clemson University, which included 31 freshwater snail records among the aquatic insect samples, and contributed numerous personally-collected samples from the upstate.  Mr. Jeremy W. Pike of the SCDNR was also most forthcoming with his personally-collected records, which total 279 to date.

As the FWGNA project has expanded, we have been accorded the opportunity to examine the systematic collections of eight national or regional museums: the National Museum of Natural History (Smithsonian), the Academy of Natural Sciences of Philadelphia, The Carnegie Museum of Natural History (Pittsburgh), the Delaware Museum of Natural History, the Virginia Museum of Natural History (Martinsville), The North Carolina Museum of Natural Sciences, the Georgia Museum of Natural History (Athens), and the Florida Museum of Natural History (Gainesville). Although the South Carolina holdings of some of these institutions have not been extensive, their curatorial staffs have always been most helpful.

Approximately 614 records were ultimately contributed by RTD in field surveys conducted from 1988 to 2022 over all ecoregions, all subdrainages, and all counties of South Carolina, using standard qualitative techniques (Dillon 2006).  Click the image above to download a pdf map.  No “absence stations” are shown. If freshwater gastropods were not collected at a site, then no record resulted.  Our entire 1,989 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 39 species and subspecies of freshwater gastropods we have confirmed from South Carolina are figured in the FWGSC gallery and distinguished on the FWGSC 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

The contributions of Jim Glover, David Eargle, Justin Lewandowski, Will Reeves, and Jeremy Pike have already been detailed above. Assistance in the field was also provided by Bryan England, Arnie Eversole, Jacob Herman, David Knott, Laura Kirk, Larry McCord, David McLean, John Robinson, Amy Wethington, John Wise, Elizabeth Gooding and especially by our student and colleague Tom Smith, whose enthusiam during the 2002-03 field season is gratefully acknowledged.

Gracious hosts at the many museums we have visited over the course of this project have included Bob Hershler at the USNM, Gary Rosenberg, Paul Callomon and Amanda Lawless at the ANSP, Tim Pearce at the CMNH, Liz Shea at the DMNH, Richard Hoffman at the VMNH, Art Bogan and Jamie Smith at the NCSM, Liz McGhee at the GMNH,  and John Slapcinsky at the FMNH.

For help with the mapping effort we thank Norm Levine and especially Doug Florian, without whose GIS skills this project would have remained an ugly heap of data.  Ms. Jasmine Wu designed the version of this site on line 2003 - 2005, and Mr. Steve Bleezarde has overseen its subsequent expansion and refinement.

> References

Dillon, R. T., Jr. 1988. The status of the catenate river snail, Goniobasis catenaria, in South Carolina. Report to the SC Heritage Trust. Columbia, SC. 16 pp. 
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. 
Dillon, R. T., Jr., & E. P. Keferl. 2000. A survey of the pleurocerid gastropods of South Carolina. Pp. 153 – 160 in Freshwater Mollusk Symposium Proceedings (Tankersley, Warmolts, Watters, Armitage, Johnson & Butler, eds.). Columbus, OH, Ohio Biological Survey.  
Gibbes, L. 1848. Mollusca. Appendix pp. xix – xxii in Report on the Geology of South Carolina (M. Tuomey, ed.).  
Harding, J., E. Benfield, P. Bolstad, G. Helfman, & E. Jones. 1998. Stream biodiversity: The ghost of land use past. Proc. Natl. Acad. Sci. USA, 95: 14843 - 14847.  
Mazyck, W. 1913. Catalog of Mollusca of South Carolina. Contributions from the Charleston Museum, Vol. II. (P. Rea, ed.). Charleston, SC, Charleston Museum. 39 pp.