The peculiar pleurocerids of the Interior Highlands I: Pleurocera potosiensis

You all like maps, am I right?  Who among my elite and erudite readership does not, at least occasionally, revel in an old-time paper map, and lament their impending extinction?

 So last summer I was taking a walk down memory lane in Derring Hall, home to both the Biology Department and the Geology Department at my alma mater [1], Virginia Tech (1973 – 1977).  And I stopped to admire a gigantic (1996) Tectonic Map of North America [2], preserved behind floor-to-ceiling Plexiglas sheeting outside the Geology Department office.  And snapped the photo below.

I was stricken by the obvious inference that at some point in the ancient past, a chunk broke off my old familiar East Tennessee stomping grounds and floated west beyond the Mississippi into the wilds of Arkansas and Oklahoma.  That chunk is the Ouachita Mountains.  Indeed, the tectonic theory of North America suggests that the Ouachita Mountains and the Appalachians are “sisters,” created together by the collision of the Gondwanan plates around 300 mya, subsequently separated by the Cretaceous Embayment.

 

Like most of us here in The East, I tend to lump the Ouachita Mountains together in my mind with the Ozark Highlands, but the Ozarks were uplifted as a dome and subsequently dissected.  That rugged region, extending north from NW Arkansas well into Missouri, is not visible in the 1996 map above.  I cannot find any consensus on the date or cause of the Ozark uplift; it may also have been a function of the Paleozoic orogeny that formed Ouachita Mountains, or may have been post-Paleozoic.  That doesn’t matter for the yarn I’m fixin’ to spin.

 

Melania potosiensis [6]

The most important thing is the snails.  Today, the characteristic freshwater gastropod of the USGS Interior Highlands Physiographic Division, which includes the Ozark Highlands, the Ouachita Mountains, and the Arkansas Valley between them, is Pleurocera potosiensis.  That snail is a regional endemic – widespread and locally quite common in rivers and streams throughout the physiographic division, unknown elsewhere.  Shi-Kuei Wu and colleagues [3] documented populations across the entire southern half of Missouri, an observation we have now thoroughly confirmed [FWGMO map].  Christian and Hayes [4] reported P. potosensis populations equally widespread across the northwestern quarter of Arkansas.  The species range also extends westward into Oklahoma, and touches the SE corner of Kansas [FWGGP map].  Further south, populations of P. potosiensis become less common in tributaries of the Arkansas River, and spotty in tributaries of the Ouachita.

Isaac Lea’s brief, Latinate description of Melania potosiensis appeared in 1841 [5], as #46 in that same “litter of 57 pleurocerid puppies” I catalogued in my essay of [20Aug25], with a more complete English description and figure following in 1843 [6].  Tryon [7] transferred the nomen to Goniobasis, reprinting Lea’s 1843 description verbatim, while adding, perceptively, 

“Were it not for the wide differences of locality I should suspect this to be identical with simplex.  I have not seen specimens, but the figure and description are certainly very close to that species.”

Goodrich [8] recognized four subspecies.  The most widespread he identified as Goniobasis potosiensis plebius (Anthony 1850), which he considered common in rivers and creeks throughout the Ozarkian area of Missouri, Arkansas, and Eastern Oklahoma.  The typical subspecies Goniobasis potosiensis (ss) he considered “a shell of the upland streams of a few Missouri counties” only.  Goodrich also recognized a Goniobasis potosiensis crandalli (Pilsbry 1890) “known only from Mammoth Springs, Fulton County, Arkansas” and a Goniobasis potosiensis ozarkensis (Call 1886) which he considered a “depauperate” form [9, 10], “only from springs of Shannon, Carter, Washington, Dent, and Camden counties, Missouri.”  Burch [11] transmitted Goodrich’s entire four-subspecies system along with their ranges verbatim, pausing only to swap out the well-established genus Goniobasis for the zombie taxon [12] Elimia.

 

As a laboratory for the study of evolution, the widely-dispersed and genetically diverse Ozark/Ouachita populations of P. potosiensis may rival the Pleurocera proxima populations of the southern Appalachians [14].  By the Grace of God, they seem to have slipped through 200 years of malacological malpractice to arrive in the 21st century almost unsplit by taxonomic exuberance.  Our colleague Russ Minton and his coworkers took advantage of this happy situation in both a shell morphological study [15] published in 2011, and in a 2017 study of intraspecific genetic divergence [16].

 

The 2011 paper, a landmark-based study of 500 individual shells sampled at 25 m intervals from a spring run and adjacent tributary of the Ouachita River in Garland County, Arkansas, was most memorable for its peculiar Figure 1.  True to the school of landmark-based morphometrics, there was no scale on Minton’s photo, reproduced below.  The caption simply read, “Morphological variation in Elimia potosiensis from Arkansas.”

Minton et al. [15] Figure 1

The first thing that struck me when I read Minton's 2011 paper some years ago was that the second shell (B) was clearly that of Leptoxis arkansensis, not P. potosiensis at all.  I’m sure that’s a common mistake, to naïve eyes.  I myself had no field experience in The Interior Highlands until 2024.  All I knew about the malacofauna of that biogeographically fascinating part of the world until quite recently was what I had learned from a week studying the Wu-Oesch-Gordon Missouri collections at the University of Colorado Museum in 2021, and even there I found some not-insubstantial Leptoxis/Pleurocera confusion.

But what really struck me upon my first reading of Minton’s 2011 morphometric study was that third shell (C).  It was clearly out of scale with the other two – probably 30% magnified, by my eye.  And recalling the words of Tryon, I found that shell completely indistinguishable from my old friend from the East, Pleurocera simplex. 

 

I picked up my first Pleurocera simplex when I was a student at Virginia Tech back in 1975, and since then have sampled hundreds of populations from SW Virginia all across Tennessee, Kentucky, and north Alabama.  I have published five papers and notes on P. simplex thus far [17], supplemented by at least eight blog posts.  Rob Dillon knows Pleurocera simplex.  Were populations of P. simplex on that plate-tectonic raft when it broke loose from its Tennessee moorings and washed up on the banks of the Wide Missouri way back in the Paleozoic?

 

Russ Minton’s 2017 paper was an even more interesting read.  He and his colleagues reported the results of two separate studies, a fine-scale study using ISSR markers very similar to the allozyme study I published on P. proxima way back in 1988 [14], and a study of 16S sequence divergence at the scale of many of the allozyme studies I published on P. proxima and others in the early-2000s [18].  The fine-scale study was poorly designed, with only 10 snails sampled for each of 12 sites down approximately 500 meters of stream, such that the ISSR markers (110 unique genotypes among the 120 individuals) returned no results.  But the study of mtDNA sequence divergence was fascinating.

Adapted from Figure 1 of Minton et al [16]

Minton and colleagues sequenced the 16S gene from 61 individual snails identified as “Elimia potosiensis” from 16 sites in southern Missouri, 14 sites in northern Arkansas, and 1 site in eastern Oklahoma.  Their map of sample sites, color-coded by drainage system, is reproduced above. This is the second-best data set [19] on interpopulation mtDNA sequence divergence ever published for any nominal species of pleurocerid snail.

 

Minton discovered four strikingly different sets of sequences, each about 10% different from the other three, none of which demonstrated any correlation to geography whatsoever.  Minton’s Figure 4 is reproduced below.  I have labelled those four sets of haplotypes X, Y, Z, and L.

 

Who among my loyal readership finds this result surprising, in the least?  How many blog posts have I dedicated to the phenomenon of mitochondrial superheterogeneity in freshwater gastropods [20], since Bob Frankis and I first stumbled upon the phenomenon [21] back in 2004?  Speaking now to any new visitors we might be entertaining in the columns of the FWGNA Blog this month, and to any other readers who might otherwise imagine that double-digit mitochondrial sequence diversity is unusual within pleurocerid populations, you are earnestly invited to footnote [22] for approximately 30 minutes of remedial study. 

Adapted from
Minton [16] Fig. 4

Ah, but.  Some of the details in Minton’s Figure 4 did not match the expectation I have developed over years of familiarity with mtSH.  Yes, Minton identified a majority haplotype, which I have labelled X, just as Whelan and Strong found in the best study of mtSH to date, their 2016 paper on Alabama Leptoxis [19].  Whelan & Strong also discovered five other haplotypes, all demonstrating double-digit sequence divergence from the majority haplotype, four of which were quite rare.  My jetlagged wildebison model would suggest that those five rare Leptoxis haplotypes had evolved somewhere far away (in snail-space or snail-time) to be scattered into the present-day study area by dirty birds.  And in the case of the Whelan & Strong dataset, we cannot identify four of those other five places.  Fine.

And yes in fact, the cluster I have labelled Y in Minton’s Figure 4 does fit our expectation for mtSH, under the jetlagged wildebison model.  That haplotype is 10.1% different from haplotype X, it is rare, and there is no divergence among the five individuals (found in three populations) carrying it.

 

But the clusters labelled Z and L in Minton’s Figure 4 do not look like mitochondrial superheterogeneity to me.  They are not rare.  Moreover, both show evolutionary structure – a branching within cluster.  Within cluster Z, for example, Population #2 branches first – the only two individuals sampled for the study, together.  Then population OK (from Oklahoma) branches off – all three of the individuals sampled, together.

 

And as I sat at my desk late one evening several years ago, examining the population OK data published in that paper, a bell tinkled way in the back of my addled brain.

 

Russ Minton only figured one shell in his 2017 paper, pasted into the corner of his Figure 2, showing a map of the sample sites for his ISSR study.  Quoting his Figure 2 caption: “Shell of E. potosiensis from population OK is shown.”  I have clipped that shell from Russ’ 2017 Figure 2 and pasted it in the lower left corner of my adaptation of his Figure 1 map above.  That is very clearly the same scaleless individual shell he labelled “Elimia potosiensis from Arkansas” in his 2011 paper.  And that shell looked as much like Pleurocera simplex in 2017 as it did in 2011.

 

All three of the individual snails that Minton sequenced from Oklahoma carried haplotype Z.  And the other 13 individuals carrying haplotype Z were scattered all across Minton’s three-state study area, as I have marked in red above.  In what direction could all those clues be leading?  Tune in next time.

 

Notes:

 

[1] For sweet, gauzy memories from my halcyon days at dear old Virginia Tech, see:

• Water hardness, stream size, and A.E. Boycott: A New River Reminiscence. [8July25]

[2] Muehlberger, W.R. (1996) Tectonic Map of North America.  American Association of Petroleum Geologists, Tulsa, OK.

 

[3] Wu, S-K., Oesch, R. & Gordon, M. (1997) Missouri Aquatic Snails. Jefferson City: Missouri Department of Conservation. 97 pp.

 

[4] Christian, A. D. and D. M. Hayes (2007) Diversity and distribution of freshwater gastropods from the Ozark Region of Arkansas.  Arkansas Game & Fish Commission, unpublished report. 34 pp.

 

[5] Lea, Isaac (1841) Continuation of Mr. Lea's paper on New Fresh Water and Land Shells.  Proceedings of the American Philosophical Society 2: 11 – 15.

 

[6] Lea, Isaac (1843) Description of New Fresh Water and Land Shells.  Transactions of the American Philosophical Society (New Series) 8: 163 – 250.

 

[7] Tryon, G. W. (1873) Land and Freshwater shells of North America Part IV, Strepomatidae.  Smithsonian Miscellaneous Collections 253: 1 - 435.

 

[8] Goodrich, C. (1939) Pleuroceridae of the Mississippi River basin exclusive of the Ohio River system.  Occasional Papers of the Museum of Zoology, University of Michigan 406: 1 – 4.

 

[9] We first mentioned “depauperization” in our essay of [20Aug25] on Melania acutocarinata.  Goodrich [10] defined “depauperization” as “the outward manifestation of disease, accident or malnutrition or a reaction to inimical environment.”

 

[10] Goodrich, Calvin (1939) Aspects of depauperization.  The Nautilus 52: 124 – 128.

 

[11] This is a difficult work to cite.  J. B. Burch's North American Freshwater Snails was published in three different ways.  It was initially commissioned as an identification manual by the US EPA and published by the agency in 1982.  It was also serially published in the journal Walkerana (1980, 1982, 1988) and finally as stand-alone volume in 1989 (Malacological Publications, Hamburg, MI).

 

[12] We reviewed the taxonomic controversy here:

• Goniobasis and Elimia [28Sept04]

It ultimately didn’t matter, because both Goniobasis and Elimia were synonymized under Pleurocera by Dillon [13] in 2011.

 

[13] Dillon, R. T., Jr. (2011) Robust shell phenotype is a local response to stream size in the genus Pleurocera (Rafinesque, 1818). Malacologia 53: 265-277. [pdf]  For a review, see:

• Goodbye Goniobasis, Farewell Elimia [23Mar11]

[14] General references on the population genetics of P. proxima:

Dillon, R.T. and G.M. Davis (1980) The Goniobasis of southern Virginia and northwestern North Carolina: Genetic and shell morphometric relationships. Malacologia 20: 83-98. [pdf]

Dillon, R.T. (1984) Geographic distance, environmental difference, and divergence between isolated populations. Systematic Zoology 33:69-82. [pdf]

Dillon, R.T. (1988) Evolution from transplants between genetically distinct populations of freshwater snails. Genetica 76: 111-119. [pdf]

Dillon, R.T. (1988) The influence of minor human disturbance on biochemical variation in a population of freshwater snails. Biological Conservation 43: 137-144. [pdf] For a review, see:

• Intrapopulation gene flow: The polymorphic Pleurocera of Naked Creek [12Oct21]

[15] Minton R.L., Lewis E.M., Netherland B, Hayes D.M. (2011) Large differences over small distances: plasticity in the shells of Elimia potosiensis (Gastropoda: Pleuroceridae). International Journal of Biology 3(1): 23 - 32.

 

[16] Minton, R.L., B.L. McGregor, D.M. Hayes, C. Paight, and K. Inoue (2017) Genetic structuring in the pyramid Elimia, Elimia potosiensis (Gastropoda, Pleuroceridae), with implications for pleurocerid conservation. Zoosystematics and Evolution 93(2) 437-449.

 

[17] General references on the population genetics of P. simplex in the Southern Appalachians:

Dillon, R. T., Jr., & G. M. Davis (1980) The Goniobasis of southern Virginia and northwestern North Carolina: Genetic and shell morphometric relationships. Malacologia 20: 83-98. [pdf]

Dillon, R. T., Jr., & J. D. Robinson (2007) The Goniobasis ("Elimia") of southwest Virginia, I. Population genetic survey. Report to the Virginia Division of Game & Inland Fisheries, 25 pp. [pdf]

Dillon, R. T., Jr. (2016a) Two reproductively isolated populations cryptic under Pleurocera simplex (Say, 1825) inhabiting Pistol Creek in Maryville, Tennessee. Ellipsaria 18(2): 15-16. [pdf]

Dillon, R. T., Jr. & J. D. Robinson (2016) The identity of the "fat simplex" population inhabiting Pistol Creek in Maryville, Tennessee. Ellipsaria 18(2): 16-18. [pdf]

Dillon, R. T., Jr. (2016) Match of Pleurocera gabbiana (Lea, 1862) to populations cryptic under P. simplex (Say, 1825) Ellipsaria 18(3): 10 - 12. [pdf]

 

[18] Regional surveys of pleurocerid population genetics:

Dillon, R. T. and A. J. Reed (2002) A survey of genetic variation at allozyme loci among Goniobasis populations inhabiting Atlantic drainages of the Carolinas.  Malacologia 44: 23-31. [pdf]

Dillon, R T. and J. D. Robinson (2009) The snails the dinosaurs saw: Are the pleurocerid populations of the Older Appalachians a relict of the Paleozoic Era?  Journal of the North American Benthological Society 28: 1 - 11.  (Rosemary Mackay Award)  [pdf]

Dillon, R. T. and J. D. Robinson (2011) The opposite of speciation: Population genetics of Pleurocera (Gastropoda: Pleuroceridae) in central Georgia.  American Malacological Bulletin  29: 159-168.  [pdf]

 

[19] The blue ribbon goes to the data set of Whelan, N.V. & E. E. Strong (2016) Morphology, molecules and taxonomy: extreme incongruence in pleurocerids (Gastropoda, Cerithiodea, Pleuroceridae). Zoologica Scripta 45: 62 – 87.

 

[20] A search on the word “superheterogeneity” using the box in the upper right of your screen will return hits in an impressive 24 essays.  And that doesn’t even include the essays I posted on the subject before I coined the term “mitochondrial superheterogeneity” in 2016.

 

[21] Dillon, R. T., and R. C. Frankis. (2004) High levels of DNA sequence divergence in isolated populations of the freshwater snail, Goniobasis.  American Malacological Bulletin 19: 69 - 77. [pdf]

 

[22] Mitochondrial superheterogeneity (mtSH), where two or more of the members of a single population demonstrate greater than 10% divergence in any single-copy mtDNA gene, not sex linked, is remarkably common in freshwater gastropods.  In pulmonate populations, I wouldn’t be surprised if most or all mtSH is ultimately traceable to cytoplasmic male sterility [23].  In prosobranch populations, however, I think mtSH is a signature of great age, plus low-frequency long distance dispersal, the “Jetlagged Wildebison Model.”  Here is a sample of my previous posts on mtSH:

• The Snails the Dinosaurs Saw [16Mar09]
• Mitochondrial superheterogeneity: What we know [15Mar16]
• Mitochondrial superheterogeneity: What it means [6Apr16]
• Mitochondrial superheterogeneity and speciation [3May16]
• Mitochondrial heterogeneity in Marstonia lustrica [3Aug20]
• Testing the periwinkle hypothesis [9May23]

[23] David, Patrice, Cyril Degletagne, Nathanaëlle Saclier, Aurel Jennan, Philippe Jarne, Sandrine Plénet, Lara Konecny, Clémentine François, Laurent Guéguen, Noéline Garcia, Tristan Lefébure, Emilien Luquet (2022) Extreme mitochondrial DNA divergence underlies genetic conflict over sex determination.  Current Biology 32: 2325 - 2333.  https://doi.org/10.1016/j.cub.2022.04.014.  For a review, see:

• Cytoplasmic Male Sterility in Physa! [9June22]

The Freshwater Gastropods of Missouri

The FWGNA Project is pleased to announce that a ninth region has been added to our burgeoning portfolio of online resources: The Freshwater Gastropods of Missouri, by R.T. Dillon, Martin Kohl, and Bruce Stephen.  Our coverage now extends across all or part of 23 states, from the Atlantic drainages onward into The Great Plains.

And just for fun, try entering the FWGMO site from our easy-to-use front page, freshly enhanced by our new friend Greg Nemes of Tanager Creative with a fancy clickable map, here:

FWGNA

Our survey of approximately 788 springs, streams, rivers, swamps, ponds and reservoirs across the Show-Me State yielded 1,760 records of 44 species and subspecies, eight of which are new to the FWGNA Project [1]. Fresh species pages for each of these eight brings our total coverage up to 156.  Two of the pleurocerid subspecies are new combinations, more about which in coming months.  Our database, as usual, is freely available for the asking.

The major drainage basins of Missouri, showing 788 sample sites.

We have stood on the shoulders of giants.  The giant of whom we must make special mention here is Dr. Shi-Kuei Wu, who along with Ronald Oesch and Mark Gordon published the wonderful 97-page, staple-bound report, Missouri Aquatic Snails, in 1997 [2].  We spent a very productive week working in Shi-Kui’s carefully-curated collection at the University of Colorado Museum back in 2021, ultimately yielding 1,261 (70%) of the records transmitted here.  Our new FWGMO web resource is dedicated to him.  We also owe special debts of gratitude to Leanne Elder and Hsiu-Ping Liu for hosting us graciously in the collection and in the home, respectively.

And speaking of gracious hosts.  Our colleagues Randy Sarver and Dave Michaelson were most generous with time, talent, and seven-year-old blacktop vials of macrobenthos at the Missouri Department of Natural Resources in Jefferson City [3].  Sorting through those vials, and the meticulous records that came with them, yielded another 325 (18%) of the records in the FWGMO database.

Ste. Genevieve-Modoc Ferry at low water

The remainder of our records were personally-collected by the three of us. The vastly-trapezoidal patch of the world enclosed by the boundaries of Missouri in 1821 is flat-out gorgeous, not all over but in spots, and I for one greatly enjoyed wetting a boot toe in her sparkling waters.  We concentrated our efforts on undersampled regions and habitats, especially the main Mississippi and Missouri Rivers, which we collected at historic low waters in September of 2023.

I have cousins in St. Louis and in Moberly, about an hour north of Jeff City, and had it explained to me that Missouri is not one state but two, “Mi-zoor-ree” in the northern flatlands and “Muh-zoor-rah” in the Ozark highlands of the south.  A biogeographer might point out that the Mississippi lowlands of the bootheel region could be considered a third state, at minimum.  The freshwater gastropod fauna reflects those striking physiographic, cultural, and military [4] distinctions.  See the FWGMO Discussion [link] for an elaboration.

We have also updated our Synthesis of relative abundances across the entire 127 species, 23-state fauna covered by the FWGNA project to the present date.  This new “Version 3.2” [link] has been a long time coming.  Since our previous Synthesis v3.1 (12May22), we have added the Great Plains (1,482 records) and the Gulf drainages of Georgia (650 records) as well as the 1,760 records newly collected from Missouri, for a grand total of 25,468.  The present update has (of course) resulted in an adjustment of the incidence rankings over the entire 127 species set, the less common half of the distribution, in any case.

The Gasconade River, Osage Co.

And finally.  We gratefully acknowledge and sincerely thank Mr. Greg Nemes of Tanager Creative for his skillful enhancement of the entire FWGNA site.  In addition to the keen clickable map on the front page, Greg did a tremendous job re-wiring the site to facilitate routine maintenance and update, freshening up the fonts, adding cool new analytics and hooking up an email platform with subscription boxes at the bottom of every page, to name but a few improvements.  So, remember the little red bird with the great big bag of skills, tanager.org, when clear communication matters to your nature, science, or humanities nonprofit!

Notes:

[1] The eight new species and subspecies freshly added: Amnicola stygia, Antrobia culveri, Fontigens aldrichi, F. antroecetes, F. proserpina, Leptoxis arkansensis, Pleurocera simplex ozarkensis, P. canaliculata lawrencii.

[2] Wu, S-K., Oesch, R. & Gordon, M. (1997) Missouri Aquatic Snails. Missouri Department of Conservation, Natural History Series #5. 97 pp.

[3] We posted a photo of our handsome colleagues from the Missouri DNR late last year:

• Art, science, and public policy: A dialogue in three languages [10Dec25]

[4] Infantry representing the northern half of Mi-zoor-ree shot south with rifled muskets; Muh-zoor-rah State Guard returned fire with obsolete smoothbores.

The ICE Detention Center and the Snail

OK, listen up!  It seems likely to me that the title of this month’s essay may attract more than the usual trickle of casual surfers and random googlers to this arcane little crack in the internet.  You new visitors and guests will not find anything newsworthy in the paragraphs that follow, nor any information relevant to any ongoing controversy, nor anything interesting, entertaining, nor probably even intelligible.  And absolutely no politics!  This is a blog post written by a snail scientist, for snail scientists.  Everybody else, please go away.  You’re scaring us.

Now for my colleagues still remaining, all six of you all.  Here is the background.  In the late morning of Wednesday 1Apr26 [1] I missed two phone calls but did successfully receive a voicemail and a follow-up email from one Ms. Maddi O’Neill with the subject line, “Media request on deadline.”  In her email, Ms. O’Neill identified herself as a freelance journalist based in Baltimore. And here, verbatim, is the background she supplied, which is really all I know about the political controversy to this day:

“I'm working on a story about a proposed ICE detention center in Washington County, Maryland, and the state of Maryland's effort to block its construction through litigation. Maryland's lawsuit hinges on the need for an Environmental Impact Statement, which the feds have not completed, and points to possible harms to state-endangered species and species in need of conservation that live near the proposed detention center site. Specifically, the state references [2] … the Appalachian springsnail, and I was wondering if you'd be open to speaking with me for a story.”

A quick google search on my part reminded me [3] that the “Appalachian springsnail” is Fontigens bottimeri.  For background on the biology of that obscure little black speck of a gastropod see the FWGNA [species page], and for contextualization see my essays of [9Aug22] and [12Feb26].

At the Hopewell Road entrance.

So I returned Ms. O’Neill’s phone call right away, and we arranged a convenient time for a telephone interview a couple days later, Friday morning 3Apr26.  In the interim, I did a bit of homework – googling up more info on the proposed ICE Detention Center, located on a 54-acre site in the crotch of I-81 and I-70, just north of Williamsport. 

I initially labored under the false impression that the feds were proposing to construct a new facility.  But in fact, their proposal was to repurpose an 800,000 square foot warehouse already on that site, newly constructed (on speculation? really?) but never used [7].  The monstrosity was large enough to have two addresses: 10900 Hopewell Road and 16220 Wright Road.

And digging through the FWGNA database, I found a Fontigens bottimeri record in the Smithsonian (USNM-874706) collected by one D. Feller in 1991 from “Kemps Spring No. 4,” the lat/long coordinates of which (39.6136, -77.8136) mapped just a half mile East of 16220 Wright Road.  I also took the opportunity to email my buddy Matt Ashton at the Maryland DNR for his input but received no response [8].

I really enjoyed getting to know Ms. Maddi O’Neill, however, in our roughly 30-minute telephone conversation Friday.  It turned out that she herself was planning a field trip to hunt Fontigens in the waters around the proposed detention center.  I like that sort of positive mental attitude.  I did my best to help her over the phone, emphasizing that Fontigens populations are restricted [9] to springs and spring runs – cold, clear, pristine 100% groundwater.

And I was pleased to receive a couple follow-up texts from Ms. O’Neill Sunday afternoon 12Apr26, apparently in the field, asking for the lat/long coordinates of Kemps Spring #4, and following with several photos of individual Lymnaea humilis perched on her finger. Bless her heart!

So on 27Apr26 she texted me a link to her article, newly published in an online magazine called “Slate,” [html].  I found the article behind a paywall.  But I was so curious to read it that I ponied up the dough for a three-month subscription, so I could copy-and-paste the text into a [pdf] document, here:

An Ingenious New Strategy for Blocking ICE Detention Warehouses Depends on a Minuscule Snail, by Madeleine O’Neill.

Spoiler alert!  Our friend Maddi did not find any Fontigens bottimeri.  But by that point I had already made plans to drive up I-81 to Williamsport and do the survey right.

I laid out a sampling scheme with five sites down Semple Run (A, B, C, D, F), the little stream just beneath the gigantic warehouse at 16220 Wright Road.  I had also noticed, using the yellow man on Google street view, what looked like an old springhouse by Wright Road not 100 yards down the hill from 16220 (E). And of course, I dropped a pin (G) on 39.6136, -77.8136.  At which coordinates I could find no evidence of a spring on any map available to me.  Satellite imagery seemed to suggest that point was in somebody’s back yard.

So the bright sunny morning of Tuesday, 5May26, found me touring around the besieged little valley of Semple Run.  And the first entry into my field notebook was this: “Semple Run low and clear over silt and debris. 150 years a ditch through ag fields, a ditch under the interstate thereafter.”

Marl falls at Site (D).

From the topo maps, it had seemed possible to me that Semple Run might bear a lot higher proportion of groundwater than it actually carries here in the 21st Century.  The current picked up speed downstream, over a cobble bottom, with some marl.  But alas, at no point was the environment fit for Fontigens, headwaters to mouth [10].  I found patchy populations of the usual Physa (both acuta and gyrina) and Maddi’s Lymnaea (Galba) humilis in the five sample sites I had marked down its length, and (quite unexpectedly) a couple individual Helisoma trivolvis, doing the anceps job. No limpets.  Period.

And perhaps unsurprisingly, the Wright Road springhouse (E) was bone dry, alas again.  The ground was boggy below the springhouse, on the other side of Wright Road, no habitat for Fontigens in evidence.

Springhouse at Site (E).

And what of Kemps Spring #4?  I parked at the south end of Celeste Drive, walked over the railroad tracks, and knocked on the door of the lovely circa 1820 brick farmhouse at 39.6136, -77.8136, repeatedly.  And a dog inside barked loud enough to wake the dead.  And nobody came to the door.  So, I let myself through the gate into the back yard and toured around, finding no evidence of spring nor springhouse.

Ultimately a nice lady, in her dishabille (as my mother used to say) came out to greet me [11].  She confirmed that no spring exists on her property, nor has any spring ever existed in that neighborhood to her knowledge, although she was familiar with the dry springhouse at Wright Road, on the other side of the tracks.  It seems likely to me that the dry springhouse at site (E) was indeed built over Kemps Spring #4, with an error of 0.0012 degrees latitude and 0.0070 degrees longitude.

Big farmhouse at Site (G).

“Lovely farmland spoiled.”  That’s the last note in my field book for the morning of May 5, 2026.  And back at the truck, as I shucked off my boots, it occurred to me that same observation would apply equally to the country around my own hometown of Waynesboro [12], two hours south, in the same sprawl that has enveloped the country around Williamsport.  And indeed, sadly, the Great Valley of Virginia.  And as one of my favorite philosophers once observed, “If this valley is lost, Virginia is lost.”  And if Virginia is lost, what of America?

Notes:

[1] Yes, the thought that this might be an April Fool’s joke did occur to me.

[2] Ms. O’Neill also mentioned “the brook floater mussel, the green floater mussel,” as well as “a few species of fish.”

[3] Somewhat startlingly, the “AI overview” at the top of my google results for “Appalachian springsnail” referred back to me, myself, in a pdf document I posted on my own FWGNA site for the Commonwealth of Virginia back in 2011 [pdf].  At the request of my buddy Brian Watson, I had included the common name below the scientific name.  Otherwise, none of the other nine hits on the first page my google search for “Appalachian springsnail” were relevant [4].

[4] By contrast, my exploratory search for “Fontigens bottimeri” returned much more relevant information, including my species page on the FWGNA site.  In fact, from my search on Fontigens bottimeri I found the relevant US FWS species page, at which F. bottimeri is called the “Potomac Springsnail [5].”

[5] Whose ridiculous idea was it [6] to conjure out of thin air an elaborate parallel taxonomy of “common names” for obscure little creatures that legitimately have no common name?  When I was in fifth grade, my teacher explained that the binomial system of nomenclature was proposed by Linnaeus in 1753 to solve the chaos of multiple common names for the same organism.  Now it is happening again!  We have two “common names” for the same tiny little black speck-snail that never had a common name to begin with.

[6] Turgeon, D.D., J.F. Quinn, A.E. Bogan, E.V. Coan, F.G. Hochberg, W.G. Lyons, P.M. Mikkelson, R.J. Neves, C.F.E. Roper, G. Rosenberg, B. Roth, A. Scheltema, F.G. Thompson, M. Vecchione, and G.D. Williams (1998) Common and scientific names of aquatic invertebrates from the United States and Canada: Mollusks (second edition), American Fisheries Society Special Publication 26, Bethesda, Maryland, 526 pp.

[7] A deserted warehouse on the edge of town, seriously?  Staffed with henchmen, wearing black turtleneck sweaters, perhaps?

[8] I followed up with Matt on Tuesday morning 4/28.  He replied that “Because the State, and specifically the Secretary of DNR, is party to an ongoing lawsuit, I referred your inquiry to our Public Relations Manager, Gregg Bortz.”  I have yet to hear from Mr. Bortz.

[9] To be complete, F. nickliniana populations in the East and F. aldrichi in Missouri can extend some significant distance downstream.  But F. bottimeri populations, in my limited experience, are restricted to the springhead and immediate spring run.

[10] See Maddi’s April 27 article for a nice photo of Semple Run tumbling under Celeste Road at Site (F).

[11] I did apologize, sincerely and profusely.  Okay, it was 8:30 AM, still early, I suppose.  I honestly thought that all the racket I made on her front porch would have brought her to the door, but no.  I did not get her name.

[12] See here for a tribute to my home town of Waynesboro, Virginia:

• The Clean Water Act at 40 [7Jan13]

George Morgan Davis (1938 – 2024): The Director’s Cut

Dillon, R.T., Jr., G. Rosenberg & P.M. Mikkelsen (2025) George Morgan Davis (1938 - 2024): Life, work, and legacy.  Malacologia 68: 3 - 26. [pdf]

The email was delivered to my inbox in the mid-afternoon Thursday, June 20, 2024, and I don’t remember being terribly surprised by the news.  Dr. George M. Davis, my major advisor at Penn 1977 – 1982 was dead.  His wife, my old friend Elaine Hoagland, was asking me to pass the word along to the wider malacological community.

King George was the last monarch of American Malacology, guiding our discipline from the classical typology of the 19th century to the neoclassical typology of the present day.  I posted single-paragraph tributes on Facebook and the Mollusca list server early that next morning, and was gratified to see how rapidly the word spread.

George M. Davis (1938 - 2024)

Gary Rosenberg, George’s successor at the Academy of Natural Sciences in Philadelphia, stepped forward to offer a memorial at the annual meeting of the American Malacological Society, upcoming just six weeks away in Pasadena, and President Pat Krug found room on the program.  Gary also began to compile a bibliography of George’s published works at that time.

Elaine also mentioned to me, in the days immediately following her husband’s death, that she had separately contacted our colleague Chuck Lydeard, George’s immediate successor as Editor-In-Chief of Malacologia, about a special volume of to be published in his memory as well.  I suppose I had assumed that Gary would take the lead on George’s professional obituary for that volume, just as he had taken the lead for the oral tribute at the AMS. 

So, the email from Chuck that arrived in my inbox 15Aug25 surprised me quite a lot.  Chuck confirmed that an entire issue of Malacologia, dedicated to the memory of my influential mentor, was indeed nearing completion.  Paula Mikkelsen and Alan Kabat had joined Gary Rosenberg to compile an extensive GMD bibliography, now grown to 200 titles, together with lists of all the species and higher taxa he had described, all the species named for him, and all the articles written about him, for publication as the lead article in that memorial issue.  But none of our distinguished colleagues apparently felt called to write a biography of the man to explain all the fuss. Nor could anybody else alive on God’s green earth be found to volunteer.

 

And so at this late date, 14 months into a 15-month project, with every other option exhausted and time running out, pushed beyond the point of despair, Chuck Lydeard was contacting me to ask if I would take the lead authorship of the lead article in a George M. Davis memorial issue of Malacologia.  My coauthors Rosenberg and Mikkleson would contribute the bibliography half, and I the biography half.  My deadline would be the end of September, six weeks away.

 

And I felt duty-bound to accept.  I didn’t like George Davis.  I don’t know anybody who did.  And although I did work closely with him during that brief window 1977 – 1982, and got to know him better than I cared to during those five years, after I left Philadelphia we really did not keep in touch.  Our areas of research interest just barely intersected, and our philosophies of science not at all.

 

But George Davis helped me.  He administered the best facilities for malacological research in the world at that time, and he made the superb ANSP collections, the wonderful library, the modern laboratory, and rooms full of equipment and cabinets bulging with supplies all available to me, free and without obligation, and otherwise left me alone, and that is exactly what I needed.

 

So, I went to work on a tribute for my major advisor.   And I confess I did not quite make my deadline, but by the first week of October had a first draft ready to share with my coauthors.  Divided into six sections, that first draft reviewed George’s 60-year career, contextualized his manifold scientific contributions, and transmitted some feeling for the outsized influence he wielded in American Malacology during the latter half of the 20th Century, an influence that continues to the present day.  And in an effort to humanize the man, each of those six sections was introduced with a story, told in the first person, in which I reminisced about my own personal experiences with my major advisor in the late 1970s.

 

And I added a top layer as well.  Looking back on 20th Century Malacology from a 25-year perspective, I found myself able to trace the evolution of our entire discipline in the career of Dr. George M. Davis.  Working on his dissertation at the University of Michigan Museum of Zoology 1960 - 1965, Davis was born into classical, 19th-century typology.  But the Modern Synthesis of Darwin + Mendel was ascending, hypothesis-driven, grounded in the theory of Fisher, Haldane, and Wright, rigorously scientific.  And just dawning at that very moment was a new age of molecules and computer analysis, ultimately to devolve into a 21st-century neoclassicism just as typological as the 19th.

 

Davis did, in fact, include a set of rigorously-designed breeding experiments in his dissertation research, published in 1967, as well as classical morphological studies and remarkably forward-looking protein electrophoretic analysis.  Yet even though his breeding studies answered the question his dissertation addressed, and neither the morphology nor the molecules contributed, Davis never tested another hypothesis throughout the remainder of his 60-year career.  Quoting myself directly: 

“George Davis had been baptized Presbyterian-form in modernity with his early laboratory experiments on hybridization, sprinkled not dunked.  Then finding objective, hypothesis-driven science too constraining, he jumped over the deeper waters of Fisher, Mayr, Dobzhansky and Simpson to the Neoclassical now, drawing our discipline along with him.”

 Well, such vivid language is never going to find publication in a scientific journal, and well I knew it, even as the Christian denominations were flying off my fingertips.  That first draft of early October was edited significantly by my coauthors, as is their right.  Paula, in particular, objected to my use of the first person in the reminiscences, which I certainly understand.  But conversion to the third person and the passive voice, much color is sacrificed.  And awkwardness left in the wake.

 

And Paula, Gary, and I kept Chuck Lydeard on the cc line as we passed the drafts around.  Rather early in the process Chuck alluded to sending our manuscript out for peer review, which seemed a wry comment on the vitality of our discipline.  “I’m not saying our science is dead, but in Malacology, obituaries are peer-reviewed.”  I needn’t have worried about that step, however, as Alan Kabat ultimately contributed a couple excellent insights which I was pleased to incorporate.

 

So, the George M. Davis Memorial issue of Malacologia was published in December, and the lead article by Dillon, Rosenberg and Mikkelsen is downloadable from this [pdf] link.  Although the paper as ultimately published does convey the overall flavor of the Scotch pie I baked in September, much of the spice has been lost.

 

Then for those of my readership who prefer their monthly dose of Rob Dillon redolent of creekbank, ancient tome, and spoiled ethanol, this month I have made FWGNA Circular #9 available for download from the website, here:

 

George Morgan Davis (1938-2024): The Director’s Cut

 

This version is very nearly that first early-October 2025 draft of my manuscript, unexpurgated, with a sprinkling of subsequent improvements.  It is missing the section on George Davis’ personal life, which was subsequently added by Gary Rosenberg, as well as the complete GMD bibliography and supporting sections as contributed by Gary and Paula working together. It does conclude with a literature-cited section, to the references cited in text only.  Also included are several nice figures not appearing in the published journal article, and a couple really good stories.  Bon appetite.

Horton hears two new species of Fontigens

Wanted: Collaborator.  Washed-up malacologist tragically enthralled by The Modern Synthesis of Darwin + Mendel seeks bright young evolutionary biologist with good molecular skills and the patience to (1) slog through last month’s discursive essay, (2) wade through this month’s ridiculous essay as well, and (3) write a grant proposal accordingly.  Apply within.

Last month [12Feb26] we refreshed our collective memory on the seven species of the hydrobioid genus Fontigens that were known, at the close of the twentieth century, to inhabit caves, springs, and spring runs in the Great Valley of Virginia [1], including one that isn’t a Fontigens but should be [2], and one that hasn’t been confirmed from the Great Valley but could be.

F. malabadi, Repass Saltpetre Cave

And we reviewed the mighty works of our heroes, Wil Orndorff and Tom Malabad of the VaDCR, collecting 87 samples of tiny gastropods from caves and springs in The Great Valley 2013 – 2019 [3] and delivering them in good order to my Charleston doorstep in three batches 2018 - 2020.  Five of those samples, collected from caves in Scott and Giles Counties, contained Fontigens that were unique to my eyes, which I dissected, described, and forwarded onward to our colleague Hsiu-Ping Liu in Colorado for sequencing.  Our description of three new species was published in 2023 [4], bringing the Valley total fauna of phreatic hydrobioids up to ten.

What I did not mention last month is that one single sample, collected from Repass Saltpetre Cave in Bland County in 2019, was of a population of Fontigens bearing shells unique to my eyes, that I forwarded on to Hsiu-Ping for sequencing, from which she was unable to amplify any DNA.  Disappointed, I settled for an identification of Fontigens-orolibas-question-mark and dropped it.

And what I concluded last month’s essay with was a teaser, strongly implying that we had not heard the last of Tom Malabad and Wil Orndorff.  For their explorations of the caves, karst features, springs and spring runs of the Great Valley of Virginia have continued, even unto the present day.  And on September 24, 2024, another big batch of 52 tiny vials, each containing even bigger batches of even tinier snails, floated down upon my Charleston doorstep light as Horton’s speck.

That batch of 52 samples, collected 2020 – 2025, contained 19 vials of snails that my daddy would have dismissed as “no count” – land snails, freshwater gastropods more common in above-ground waters, and one Fontigens too busted up to identify.  Then in the 33 samples of consequence, I identified 35 populations of phreatic gastropods: 10 Fontigens orolibas, 4 F. nickliniana, 4 F. bottimeri, 3 F. morrisoni, 3 Holsingeria, 2 F. tartarea, 1 F. hershleri [5], and 8 populations of Fontigens bearing shells unlike any I had ever seen before. Almost.

Now to be quite precise.  Among those 52 samples were a pair of fresh samples, one collected in 2022 and another in 2024, from that same peculiar population inhabiting the waters of Repass Saltpetre Cave in Bland County I had flagged several years previous.  The shells borne by the Fontigens in that pair of samples reinforced the impression of uniqueness that had first struck me in the 2019 sample, characterized by tighter whorls, a smaller body whorl, and a higher spire than any Fontigens previously described.  See the figure up at the top of this essay.

Gallohan Cave #1

And also among the 52 vials that arrived on my doorstep in September were a pair of samples collected 22Jan25 and 5Aug25 from The Caverns of Natural Bridge Village in Rockbridge County, bearing shells that matched the Repass Saltpetre population. And good grief!  In a third vial, collected in 2021 from Gallohan Cave #1 way down at the tip of Virginia in Lee County, I found a mixture of 5 Holsingeria and 2 Fontigens (red arrows above) bearing that same, peculiar Repass Saltpetre shell morphology.

Here I describe a new species, Fontigens malabadi Dillon MS, in honor of my esteemed colleague Thomas E. Malabad.  The shell of Fontigens malabadi is distinguishable from that of all previously-described species in the genus by relatively tight, rounded whorls, a small body whorl, and a high spire.  The type locality is a stream in Repass Saltpetre Cave, Bland County, Virginia.  Other populations of F. malabadi are known from cave streams in Rockbridge County and Lee County, Virginia.

F. orndorffi, Kinzer Hollow Cave

But wait, there’s more.  Also among the 52 vials delivered to my Charleston address in September were three samples of Fontigens bearing shells really, seriously unlike anything I had ever seen before, not just in the published literature but in all 87 samples collected by Wil & Tom 2013 – 2019.  These were collected from Spangler Cave and Kinzer Hollow Cave way down south in Lee County, and in Rogers Belmont Cave way up north in Warren County, Va.  That last sample, just a single individual actually (red arrow below), was mixed with two individual Fontigens orolibas.

Here I describe a second new species, Fontigens orndorffi Dillon MS, in honor of my esteemed colleague William D. Orndorff.  The shell of Fontigens orndorffi is distinguishable from that of all previously-described species in the genus by relatively tight, flat-sided whorls, a small body whorl, and a high spire.  The type locality is a stream in Kinzer Hollow Cave in Lee County, Virginia.  Other populations of F. orndorffi are known from streams in Spangler Cave (Lee County) and Rogers Belmont Cave (Warren County).

Rogers Belmont Cave

These are but manuscript descriptions at present.  As I noted in last month’s essay, in this day and age it is irresponsible to formally describe a new species without genetic confirmation of some sort.  And I have none.

But let me stop right here, back out of my disorderly narrative, and try to cast a broad perspective over the entire inventory of 87 + 52 = 139 samples of tiny snails stacked at the end of my lab bench this afternoon, and all six essays I have posted on this subject thus far, 2006 - 2026 [6].  There has been an endemic radiation of Fontigentid gastropods in The Great Valley of Virginia.  And several generations of malacologists, including my own, have been Humpfing around the edges of it for years, like sour kangaroos.  

Sure, I’d be pleased to find a collaborator to sequence a couple genes on a few snails and help me with the descriptions of Fontigens malabadi and F. orndorffi, no matter how small.  But what we really need is a PI to write a big grant proposal to take all 139 little vials off the end of my lab bench and see if we can work out the fascinating history of the entire evolutionary radiation.

Because the joint distribution of these 12+ enigmatic little creatures is a codex of the Appalachian orogeny.  Exactly like the pleurocerid snails, their distributions are older – much older – than the drainage basins in which they live.  Populations of Fontigens do not give a rat’s rear end whether their cave stream is running toward the Atlantic, the Ohio, or the Tennessee.  Even modern crow-fly distance means nothing to them.  Let me give you just one example.

The Great Valley of Virginia

Bob Hershler described Holsingeria unthanksensis – certainly the most peculiar element of the fauna – as endemic to Unthanks Cave in Lee County, draining toward the Tennessee River way down in the SW tip of Virginia [2].  Since 1989, Holsingeria populations have been discovered in four other Lee County caves (Spangler, Tater, Burial, and Gibson #1).  Then in 2003, Hershler and colleagues documented a highly disjunct population of Holsingeria in Skyline Caverns, way up north in Warren County, draining through the Shenandoah River to the Atlantic [7].  And no populations of Holsingeria have ever been discovered in the 500 linear kilometers between Lee and Warren County whatsoever.

Now here in the present essay I have described a new species, Fontigens orndorffi, with exactly that same bizarre distribution.  Fontigens orndorffi co-occurs with Holsingeria in Spangler Cave, way down in Lee County, as well as in Kinzer Hollow Cave, a few km E of Spangler.  And F. orndorffi is also found in Warren County, in Rogers Belmont Cave just a couple km W of Skyline Caverns.  And no populations of F. orndorffi are known in the 500 km between Lee and Warren Counties, either.

That is not a coincidence.  These tiny snails are trying to tell us something big about the ancient history of the Southern Appalachians.  If you hear that Yopp as clearly as I do, and you want to help, apply within.

Notes:

[1] 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.  For a review and an appreciation, see:

• Springsnails of the Blue Ridge [26July06]
• My Buddy Bob [6July22]

[2] Hershler, R. H. (1989) Holsingeria unthanksensis, a new genus and species of aquatic cavesnail from eastern North America. Malac. Rev. 21: 93-100.  For more, see:

• Cave Snail Adventure [22Aug07]

[3] Actually one sample from 1987 and one from 2008.  But the rest from 2013 – 2019.

[4] Dillon, R.T., Jr., T.E. Malabad, W.D. Orndorff & H-P. Liu (2023) Three new Fontigens (Caenogastropoda: Fontigentidae) from caves in the Appalachian Ridge and Valley Province, Virginia. Pp. 283 - 306 in Dillon, R.T., Jr. et al. The Freshwater Gastropods of North America Volume V: Ohio, Cumberland, and Tennessee River Systems. FWGNA Press, Charleston. [pdf]  For a review, see:

• Three New Fontigens from Virginia [9Jan24]

[5] This is just the second population of F. hersheri ever discovered: Litton Cave #1, Lee County.

[6] In addition to my essays of 26July06, 22Aug07 and 9Jan24 linked above, one must count last month's essay (12Feb26), this month's essay (5Mar26) and my review of the 2021 molecular study published by Liu, Schroeder, Berry, and Dillon [pdf]:

• Startled by Fontigens, sort-of, I suppose [9Aug22]

[7] Hershler, R. H., H-P. Liu & F. G. Thompson (2003) Phylogenetic relationships of North American nymphophiline gastropods based on mitochondrial DNA sequences. Zoologica Scripta 32: 357-366.