> Recommendations
   Virginia Atlantic Drainages

Virginia's Wildlife Action Plan was developed in 2005 under the US Fish & Wildlife Service's State Wildlife Grant program.  The plan lists 20 species of freshwater gastropods as being needy of conservation, ranked into four tiers - Tier 1 (critical conservation need), Tier 2 (very high), Tier 3 (high), and Tier 4 (moderate).  Twelve of these 20 species might range into Virginia Atlantic drainages, and as such are covered by the present report (Table 2).

Over the course of the present survey we collected 13 freshwater gastropod species at fewer than ten sites, and failed to collect 10 additional species that might have been expected to inhabit Virginia Atlantic drainages, based on previous reviews (Table 1).  Ten of these 23 species were also listed on the Virginia CWCS.  These have been transferred to Table 2, along with their abundance data.

Four of our 23 species are exotic or invasive – Bithynia tentaculata, Viviparus georgianus, Bellamya chinensis and B. japonica.  That these four have appeared infrequently in our collections is a blessing.

Two of our 23 are certainly undercollected – Littoridinops tenuipes and Pomatiopsis lapidaria.  Littoridinops populations inhabit brackish and tidal freshwater habitats inadequately covered by this survey.  Pomatiopsis is amphibious, primarily inhabiting moist and muddy habitats above water level, and is more widespread in interior drainages than in regions draining east to the Atlantic.

Nine of our 23 species are on the edges of more extensive ranges in the present study area, spottily distributed or accidentally dispersed in Virginia.  Aplexa elongata, Promenetes exacuous, and Planorbula armigera are elements of the marshy or vernal faunas of northern states, while Ferrissia parallela, Gyraulus deflectus, and the two Valvata species are more common in northern lakes.  Hebetancylus excentricus is primarily an inhabitant of marshes and ponds in Florida and the south.  Goniobasis catenaria dislocata is a morphological variant of G. catenaria catenaria, possibly ecophenotypic in origin, and ranges primarily south through the Carolinas to Georgia.  All 9 of these species are more common elsewhere, and their rarity in Virginia Atlantic drainages no cause for conservation concern.

The conservation status of the remaining eight species bears closer examination.  This subset includes four epigean or phreatic hydrobiids (Holsingeria species 1, Fontigens orolibas, F. morrisoni, and F. bottimeri) three inhabitants of medium to large Piedmont rivers (Lioplax subcarinata, Gillia altilis, and Somatogyrus virginicus), and the obscure pulmonate Stagnicola neopalustris.

Like all the biotic elements of Virginia piedmont rivers, Lioplax, Gillia and Somatogyrus have doubtless suffered greatly from the high sedimentation loads that have eroded into their habitats from intensive agricultural practices for over 200 years.  All three of these species may have at one time been common throughout the southern Atlantic drainages.  Today populations of Lioplax and Gillia have nearly disappeared from Virginia, South Carolina and Georgia, and seem only locally common in North Carolina.  Somatogyrus seems to have been somewhat less impacted over the four state area, by virtue of its range into smaller rivers.  But the conservation status of all three of these species is a legitimate object of concern.

Of the four epigean hydrobiids, Fontigens orolibas is by far the most secure.  The monograph of Hershler et al. (1990) catalogued about 40 populations in a variety of caves, springs and seeps over approximately 15 counties.  Our 2007 audit of these data returned positive results in five of seven localities we were able to revisit.  The two other Fontigens species, F. bottimeri and F. morrisoni, are both much narrower in their ranges and habitat requirements.  Hershler and colleagues listed just seven localities for the former and four for the latter.  The springs and cave streams inhabited by Fontigens bottimeri and F. morrisoni merit protection.

The taxonomic status of "Holsingeria species 1" remains in limbo.  Hershler noted, in his (1989) description of H. unthanksensis from Lee County, that "numerous lots" of a "probable additional congener" from Skyline Caverns in Warren County were available in the collections of the US National Museum, and that "efforts to collect living representatives of these snails are in progress."  But 20 years later, the "Skyline Caverns Snail" remains undescribed.  We fear that the introduction of rainbow trout into the Cavern pools, together with the ecosystem enrichment and disruption that attends such practices, may have foreclosed any further research in this direction.

Stagnicola neopalustris has not been re-collected since its original description from Orange County, Virginia, by F. C. Baker (1911).  If it was indeed a Stagnicola, a Virginia population would be extralimital.  Snails of the subgenus Stagnicola (as Baker applied the taxon) typically range through the northern states and Canada, inhabiting marshes, bogs, and lake margins.  All 24 species and subspecies Baker assigned to the taxon in 1911 were synonymized under the circumboreal Lymnaea palustris by Hubendick (1951).  Its seems possible that Baker’s neopalustris may have represented a senescent or deformed Lymnaea columella.  In any case, it seems unlikely to us, even should a population of oddly-shaped lymnaeids be rediscovered in Orange County in the present day, that “Stagnicola neopalustris” would prove to be a valid specific nomen.


> References

Baker, F.C. 1911. The Lymaeidae of North and Middle America, Recent and Fossil. Chicago Academy of Sciences Special Publication No. 3., Chicago, Illinois.  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.  Hubendick, B. (1951) Recent Lymnaeidae.  Their variation, morphology, taxonomy, nomenclature, and distribution. Kungl. Svenska Vetensk. Akad. Handl., 3, 1-223.  Virginia Department of Game and Inland Fisheries (VADGIF 2005)  Virginia Wildlife Action Plan.  VA: Richmond.