The Freshwater Gastropods of North Carolina
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> Introduction
Like most states
of the Union, at no time in its history has North Carolina seen a
comprehensive field survey of its freshwater gastropod fauna. Charlotte
Dawley (1965) published a simple checklist based on collections then
housed at the Academy of Natural Sciences and the University of
Michigan, together with her personal observations and those of Walter
(1956). From NC Atlantic drainages she documented the
22 species listed (together with 8 synonyms) in the rightmost
column of Table 1. Much more recently, the NatureServe
Explorer database
(accessed 6/06) contained records for 58 species of freshwater
gastropods in North Carolina, generally inferred from the North
American ranges of the individual species. Subtracting synonyms
and species restricted to interior drainages would reduce this
list to the 39 taxa reported in the center column of Table 1. From
a systematic standpoint, however, the freshwater gastropods
of North Carolina were essentially unsurveyed prior to the present
report.
Nevertheless, the state has seen considerable primary research conducted on its
freshwater gastropod populations. North Carolina populations of the pleurocerid
genus Goniobasis have served as important models in evolutionary biology
(Dillon 1984, 1988, Dillon & Reed 2002, Dillon & Frankis 2004, Stiven & Kreiser
1994), as well as occasional studies of a more ecological nature (Foin & Stiven
1970, Dillon & Davis 1991). NC populations of Campeloma have figured
in research on the origin of parthenogenesis (Johnson 1992). A great many important
studies on the relationships between pulmonate snails and their trematode parasites
have been conducted in Charlie’s Pond, north of Winston-Salem (e.g., Snyder & Esch
1993, Sapp & Esch 1994, Esch et al. 1997), and some parasitological interest
has been directed toward NC populations of G. proxima as well (Barger & Esch
2000, Lang 1968). A unique species of caddisfly has recently been described from
the Little River of Montgomery County, with a larval stage predatory on Somatogyrus
virginicus (Morse & Lenat 2005). The ecological experiments of McCollum
et al. (1998), although conducted in aquaria, were designed to mimic natural
communities of fish, snails, and periphyton typical of the Raleigh-Durham area.
North Carolina spans four ecoregions (at US EPA Level III): Blue Ridge,
Piedmont, the Southeastern Plains and the Middle Atlantic Coastal
Plain. These areas drain toward the Atlantic through six major river
systems: the Dan/Roanoke, the Tar, the Neuse, the Cape Fear, the
Yadkin/Pee Dee, and the Catawba, as well as several smaller systems.
The Blue Ridge ecoregion also extends across the eastern continental
divide to include one tributary of the Ohio River and several
tributaries of the Tennessee River only peripherally dealt with in this
study.
The present survey focuses on the gastropod fauna of the Atlantic
drainages. We are aware of several nominal species whose North Carolina
ranges include only interior drainages, including Leptoxis
praerosa, Leptoxis dilatata, and Goniobasis christyi (or interrupta.) Treatment of these species will be deferred to future FWGNA web resources still under development.
> Methods
The database here analyzed
includes 5,645 records from three primary sources. The largest fraction (2,533
records) are from field observations collected by contractors and staff of
the NC Wildlife Resources Commission 1977–2002 and tabulated by BTW. A
total of 805 records are from the catalogued collections of the North Carolina
State Museum in Raleigh, 1958–2004. An additional 2,256 records are from
macrobenthic collections made by the NC Division of Water Quality 1985–2005,
housed at the NCSM but not catalogued as of 2005. The remainder of the records
were collected by RTD from 2000–2005, largely funded through a subcontract
with Normandeau Associates related to FERC relicensing of dams in the Yadkin
drainage.
Sample sites were located throughout the state, in all ecoregions, all drainages,
and all counties. A map (in PDF format) showing the distribution of sites is
available as Figure 1. No “absence stations” are shown. If freshwater
gastropods were not collected at a site, then no record resulted.
Collecting methods have varied greatly. The NCDWQ samples are
semi-quantitative, taken by EPA standard methods (Barbour et al. 1999)
combining kick-nets, timed searches, etc. Other collections were
entirely qualitative, the result of simple untimed searches. All
collections are now or soon will be housed at the NCSM, or (in the case
of NCWRC) are extensively vouchered there. Our entire 5,645 record
database is available (as an excel spreadsheet) from the senior author
upon request.
> Acknowledgements
> References
Robert T. Dillon, Jr.
Department of Biology, College of
Charleston
Charleston, SC 29424
P: 843.953.8087
F: 843.953.5453