> Introduction

The 102,671 km² enclosed by the Commonwealth of Virginia includes seven (Level III) US EPA ecoregions and four (Level 2) USGS hydrologic units – Mid Atlantic, South Atlantic, Tennessee and Ohio.  The survey of freshwater gastropods we report here is focused on the eastern 75% of the state only, draining from headwaters in the Ridge & Valley ecoregion eastward through the Blue Ridge, Piedmont and Coastal Plain to the Atlantic Ocean.  Our long term plans include an extension of coverage over the western 25% of the state, including tributaries of the Ohio River and Tennessee River draining westward, as resources permit.

The published literature includes two previous statewide inventories of Virginia’s freshwater gastropod fauna, as well as several regional surveys.  Prominent in the latter category are the surveys conducted in the coastal plain by Rehder (1949), in the James River Basin and Hanover County by Burch (1950, 1952), again in the James River by Clench and Boss (1967), in the Holston River by Stansbery (1972, Stansbery and Clench 1974a, 1974b, 1977), and in the New River by Dillon & Benfield (1982).  Hershler and colleagues (1990) combined museum records together with field collections in their comprehensive review of the Fontigens species inhabiting Virginia and surrounding states.  Beetle (1973) compiled a statewide checklist from museum records, which Stewart & Dillon (2004) included with their larger review of all published accounts and records of freshwater gastropods in the state.  But the present survey reports the first comprehensive inventory of Virginia's freshwater gastropod fauna to be based on original field collections.

Several species of freshwater snails have been originally described from Virginia type localities in the modern era.  Somatogyrus virginicus was described from a population in the Rapidan River in Culpeper County (Walker 1904).  Baker (1911) described the lymnaeid Stagnicola neopalustris from Orange County Virginia, although the species has not been subsequently collected.  Hubricht (1957) described Fontigens orolibas from springs and cave streams in Shenandoah National Park, and Hershler et al. (1990) added F. morrisoni from Bath and Highland Counties.  Holsingeria unthanksensis was described from a population inhabiting Unthanks Cave, in the southwestern corner of Virginia, by Hershler (1989).

Virginia populations of freshwater gastropods have also served as models for basic research of an ecological or evolutionary nature.  The distribution and abundance of Leptoxis populations in small tributaries of the James River has been studied by Miller (1985) and Stewart & Garcia (2002).  Dillon has conducted extensive evolutionary studies of Goniobasis populations from the southern and western regions of the state (Dillon & Davis 1980; Dillon 1986, 1988, 1989).  In the most intensive freshwater gastropod conservation initiative to date in the region, Io fluvialis was reintroduced to sites in southwestern Virginia in the 1970s where it had suffered local extinctions (Ahlstedt 1979).  The reintroduction was successful, as several populations were restored by the early 1990s (Ahlstedt 1991).

> Methods

The database here analyzed contains 1,447 records.  A subset of 372 records were gathered by RTD from a review of the macrobenthic collections made by Virginia Commonwealth University biologists as a part of the INSTAR project.  An examination made by RTD of collections held by the VADEQ office in Glen Allen on 7/07 yielded 126 records, and a 1/05 visit to the Virginia Museum of Natural History in Martinsville by RTD and BTW contributed 121 records.  The remaining 828 records were almost primarily collected by RTD, BTW, and TRS in field surveys from 2002 to 2007 in all ecoregions, all drainages, and all counties, using standard qualitative techniques (Dillon 2006).

A map (in PDF format) showing the distribution of our sample sites is available as Figure 1 (not as yet available.)  No “absence stations” are shown.  If freshwater gastropods were not collected at a site, then no record resulted.  Our entire 1,447 record database is available (as an excel spreadsheet) from the senior author upon request.  Data obtained solely through the Virginia Department of Game & Inland Fisheries will require DGIF approval prior to release.


> Acknowledgements

We thank Dr. Len Smock, Drew Garey, and their colleagues at VCU for providing access to the INSTAR collections and hosting us graciously during our visits to Richmond.  Our appreciation is also due to Dr. Richard L. Hoffman of the VMNH and Bill Shanabruch of the VADEQ office in Glen Allen for providing access to the collections under their care. The success of this project has in large part depended on the GIS and data analysis skills of Dr. Doug Florian, and the webmastery of Mr. Steve Bleezarde, to whom we offer our sincere thanks.


> References

Ahlstedt, S.A. 1979. Recent mollusk transplants into the North Fork Holston River in southwestern Virginia. Bulletin of the American Malacological Union 1979:21-23.  Ahlstedt, S.A. 1991. Reintroduction of the spiny riversnail Io fluvialis (Say, 1825) (Gastropoda: Pleuroceridae) into the North Fork Holston River, Southwest Virginia and Northeast Tennessee. American Malacological Bulletin 8:139-142.  Baker, F.C. 1911. The Lymaeidae of North and Middle America, Recent and Fossil. Chicago Academy of Sciences Special Publication No. 3., Chicago, Illinois.  Beetle, D.E. 1973. A checklist of the land and freshwater mollusks of Virginia. Sterkiana 49:21-35.  Burch, J.B. 1950. Mollusks: In James River Project Committee of the Virginia Academy of Science, ed., The James River Basin, Past, Present, and Future., Virginia Academy of Science, Richmond, Virginia.  Pp. 129-137.  Burch, J.B. 1952. Preliminary checklist of Mollusca of Hanover County, Virginia. Nautilus 66:60-63.  Clench, W.J. & K.J. Boss. 1967. Freshwater Mollusca from James River, VA and a new name for Mudalia of authors. Nautilus 80:99-102.  Dillon, R.T., Jr., and G.M. Davis. 1980. The Goniobasis of southern Virginia and northwestern North Carolina: genetic and shell morphometric relationships. Malacologia 20:83-98.  Dillon, R.T., Jr. & E.F. Benfield 1982. Distribution of pulmonate snails in the New River of Virginia and North Carolina, U.S.A.: interaction between alkalinity and stream drainage area. Freshwater Biology 12:179-186.  Dillon, R.T., Jr. 1986. Inheritance of isozyme phenotype at three loci in the freshwater snail, Goniobasis proxima: mother-offspring analysis and artificial introduction. Biochemical Genetics 24:281-290.  Dillon, R.T., Jr. 1988. Evolution of transplants between genetically distinct populations of freshwater snails. Genetica 76:111-119.  Dillon, R.T., Jr. 1989. Karyotypic evolution in pleurocerid snails. I. Genonomic DNA estimated by flow cytometry. Malacologia 31:197-203.  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.  Hershler, R. 1989. Holsingeria unthanksensis, a new genus and species of aquatic cavesnail from eastern North America. Malacological Review 22:93-100.  Hershler, R., J.R. Holsinger & L. Hubricht 1990. A revision of the North American freshwater snail genus Fontigens (Prosobranchia: Hydrobiidae). Smithsonian Contributions to Zoology 509:1-49. Hubricht, L. 1957. New species of Fontigens from Shenandoah National Park. Nautilus 71:9-10.  Miller, C.  1985.  Correlates of habitat favorability for benthic macroinvertebrates at five stream sites in an Appalachian Mountain drainage basin, USA.  Freshw. Biol. 15: 709-733.  Rehder, H.A. 1949. Some land and freshwater mollusks from the coastal region of Virginia and North and South Carolina. Nautilus 62:121-126.  Stansbery, D.H. 1972. The mollusk fauna of the North Fork Holston River at Saltville, Virginia. Bulletin of the American Malacological Union 1971:45-46.  Stansbery, D.H. & W.J. Clench 1974a. The Pleuroceridae and Unionidae of the North Fork Holston River above Saltville, Virginia. Bulletin of the American Malacological Union 1974:33-36.  Stansbery, D.H. & W.J. Clench 1974b. The Pleuroceridae and Unionidae of the Middle Fork Holston River in Virginia. Bulletin of the American Malacological Union 1974:51-54.  Stansbery, D.H. & W.J. Clench 1977. The Pleuroceridae and Unionidae of the upper South Fork Holston River in Virginia. Bulletin of the American Malacological Union 1977:75-79.  Stewart, T.W. & R.T. Dillon, Jr. 2004. Species composition and geographic distribution of Virginia’s freshwater gastropod fauna: a review using historical records. American Malacological Bulletin 19:79-91.  Stewart, T. W. & J. E. Garcia. 2002.  Environmental factors causing local variation in density and biomass of the snail Leptoxis carinata, in Fishpond Creek, Virginia.  Am. Midl. Natur. 148: 172-180.  Walker, B. 1904. New species of Somatogyrus. Nautilus 17:133-142.