> Recommendations:
Georgia Atlantic drainages

Prior reviews of the conservation status of the Georgia Atlantic freshwater gastropod fauna have justifiably focused on the substantial number of endemic or narrowly-restricted species of the family Hydrobiidae inhabiting the region.  As of 1994, M. agarhecta and Somatogyrus tenax were candidates for listing as federally threatened or endangered species (Neves et al. 1997), the former being classified by the Association for Biodiversity Information (ABI) as “critically imperiled” globally (Herrig and Shute 2002).  The only Atlantic-drainage gastropod species listed as "high priority animals" in the recent Comprehensive Wildlife Conservation Strategy for Georgia were hydrobiids - Marstonia agarhecta, Somatogyrus tenax, and S. alcoviensis, (GaCWCS 2005).  The NatureServe Explorer ranks four Georgia Atlantic hydrobiids in its database as either "G1" (critically imperiled) or "G2" (imperiled) - the three mentioned above as well as the more recently described Marstonia gaddisorum (Thompson 2005).

The two Somatogyrus are indistinguishable from the widespread S. virginica, and in our opinion are its junior synonyms.  But M. agarhecta (with M. gaddisorum) is distinct, the two taken together apparently restricted to isolated small springs and spring-fed creeks in three counties (Wilcox, Pulaski, and Laurens).  Clearly the agarhecta + gaddisorum populations are legitimate objects of some conservation concern.

The Georgia Atlantic fauna includes four other hydrobiid species with narrow or limited ranges: Notogillia sathon, Spilochlamys turgida, Marstonia halcyon, and Floridobia species A.  Notogillia and Spilochlamys have distributions very similar to that of agarhecta + gaddisorum: the same scattered springs and small creeks in Pulaski, Wilcox, and Laurens Counties.  It is odd that neither Notogillia nor Spilochlamys was mentioned in the Georgia CWCS, and that both species are listed as G5 ("secure") by NatureServe.  These species are as worthy of careful monitoring as M. agarhecta.  And since the ranges are almost identical, no additional effort would be required.

Marstonia halcyon and the undescribed Floridobia species A both appear to be endemic to the same (roughly 100 km) stretch of the Ogeechee River in Georgia's eastern coastal plain.  Although the status of these two hydrobiid populations does not appear as precarious as that of Notogillia, Spilochlamys, and M. agarhecta + gaddisorum, a single calamitous spill of some pollutant into the Ogeechee River above Millen could induce their extinction.  And again, both M. halcyon and Floridobia could be monitored with identical effort.  Some such effort is warranted.

In addition to the hydrobiids mentioned above, the NatureServe Explorer also ranks three nominal species of pleurocerids from Georgia Atlantic drainages as either G1 or G2 - Goniobasis (or "Elimia") darwini, G. mutabilis, and G. timida.  The two former nomena are junior synonyms of the widespread G. catenaria, and timida is a subspecies of Goniobasis floridensis, also quite common in other drainage systems (Dillon & Robinson in review).  The remainder of the (32) freshwater gastropod species of Georgia Atlantic drainages listed by NatureServe were ranked G4 (apparently secure) or better.


>References

Dillon, R. T., Jr. & Robinson, J. D. (in review)  Genetic relationships among populations of Goniobasis ("Elimia") from central Georgia.  GaCWCS (2005)  A Comprehensive Wildlife Conservation Strategy for Georgia.  Georgia DNR, Wildlife Division.  Social Circle, GA.  202 pp.   Herrig, J., and A P. Shute (2002)  Aquatic animals and their habitats. pp. 537-579 in Wear, D.N., and J.G. Greis (eds). Southern forest resource assessment. U.S. Department of Agriculture, Forest Service, Southern Research Station, Asheville, North Carolina. General Technical Report SRS-53.    Neves, R.J., A.E. Bogan, J.D. Williams, S.A. Ahlstedt, and P.W. Hartfield (1997)  Status of aquatic mollusks in the southeastern United States: a downward spiral of diversity. pp. 43-85  in Benz, G.W. and D.E. Collins (eds.). Aquatic Fauna in Peril: a Southeastern Perspective. Southeast Aquatic Research Institute Special Publication 1, Lenz Design and Communications, Decatur, Georgia.   Thompson, F. G. (2005)  Two new species of hydrobiid snails of the genus Marstonia from Alabama and Georgia.  Veliger 47: 175-182.  Watson, C.  (2000)  Results of a survey for selected Hydrobiidae (Gastropoda) in Georgia and Florida.  Proc. First Freshwat. Moll. Conserv. Soc. Sympos. 233 - 244.