Dr. Rob Dillon, Coordinator





Friday, June 5, 2020

What is Melania edgariana?


If you follow the FWGNA blog on a regular basis, bless your heart, it is possible, indeed likely, that a terrible revelation has by now dawned upon you.  You have become ensnared in a series of essays on shell morphological variation in the pleurocerid fauna of the Tennessee/Cumberland that began back in August of 2019, eight episodes ago, with no end in sight.

And even as this soggy mat of dubious science, arcane history, and overwrought pontification has unrolled these many months, the supercilious weaver who labors today to augment its warp and weft expects you to remember threads now gone, and appreciate patterns as yet emerging. 

But he will deign to refresh your memory, briefly.  In August we heard the story of Captain S. S. Lyon, who in 1862 sent a sample of pleurocerid snails collected from Cumberland Gap to the eminent scientist Dr. Isaac Lea in Philadelphia.  Although Lea gave four new names to this collection of snails, the evidence available to us today suggests that only two species were actually present, best identified as Pleurocera simplex (Say 1825) and P. troostiana (Lea 1838).  And in Gap Creek, at least, their shell morphology seemed to vary together.  Both populations were dwarfed upstream and typical downstream, demonstrating the phenomenon we abbreviate CPP, for “cryptic phenotypic plasticity,”

In September and October, we learned that populations of P. simplex range throughout Tennessee and Kentucky, varying strikingly in their shell morphology, likely as a consequence of CPP.   And in December, January, April and May, we documented a similar but even more extreme phenomenon in populations of Pleurocera troostiana, inhabiting a big swath of the Tennessee drainage from SW Virginia through East Tennessee into North Alabama. Everywhere in this vast region we have seen simplex and troostiana living side-by-side, varying together.

Melania edgariana [1]
Now the main theme of our September post was this.  In the Cumberland River drainages of Middle Tennessee and Kentucky, populations of Pleurocera simplex inhabit larger rivers than they do in the Tennessee River drainages further east.  And correlated with this range extension, they bear shells that are larger, broader, and heavier than the P. simplex populations of East Tennessee drainages.  The middle Tennessee populations are so different from populations of East Tennessee that they have traditionally been identified by a different specific nomen, ebenum (Lea, 1841), and in some cases even a different genus, Lithasia.

Might the range of P. troostiana also extend through the Cumberland drainages of Middle Tennessee into Kentucky as well?  Perhaps shifting shell morphology in parallel with P. simplex, demonstrating similar levels of CPP?

Yes.  In 1841 Isaac Lea published a brief, Latinate description of “Melania edgariana,” with full description and figure in 1843, sent to him from “Cany Fork, Tenn.” by Mr. S. M. Edgar [1].  This must be a misspelling of Caney Fork, the tributary of the Cumberland River from which we extracted the Pleurocera simplex populations we studied in September.   Lea described the shell of edgariana as “spire elevated,” and enthused “it is remarkable for being folded and transversely striate on all the whorls.”

In 1873 G. W. Tryon [2] synonymized edgariana under Goniobasis nassula, which T. A. Conrad had described from the Big Spring at Tuscumbia, Alabama, in 1834 [3].  Tryon said, and I quote verbatim: “Mr. Lea agrees with me that his Edgariana is a synonym of nassula.”  Lea despised Conrad [4].  Wouldn’t you have loved to be a fly on the wall when Lea and Tryon had their conversation about edgariana?

Goodrich disagreed with Tryon, however, removing Goniobasis edgariana from under the synonymy of Conrad’s G. nassula, suggesting for the range of edgariana “Streams of Cumberland, Duck and Elk Rivers, Tennessee” and listing 13 synonyms underneath it [5].

And as usual, I’m with Goodrich.  I really think that the population of pleurocerids inhabiting Tuscumbia’s Big Spring is something else.  The biological situation at Tuscumbia’s Big Spring is even more fascinating than the situation at Huntsville’s Big Spring, and I feel sure we will come back to Tuscumbia in some future post.  But for now, we will stipulate that Lea’s edgariana and Conrad’s nassula are two entirely different things, and that’s all I’ve got to say about that.

So back to the Caney/Collins River system.  It will be remembered from our September post that populations of Pleurocera simplex become progressively more robust and heavily-shelled from headwater tributaries on the west slope of the Cumberland Plateau north toward the confluence of the Caney with the Cumberland River at Carthage, TN.  I’ve taken a slice from the map I published in September and expanded it below, retaining simplex sites J, K, and L.  

(J) Collins River, (I) Center Hill Lake, (H) Caney Fork
The cryptic phenotypic plasticity demonstrated by populations of P. simplex in the Caney/Collins is especially important for the argument I’m preparing to advance below.  So if my September post is not vivid in your memory, I’d be gratified if you opened this link [4Sept19] in a separate window and reviewed the material featured therein.  We will wait for you.

Are you back?  Good.  Going forward now.

Crawling around on the rocks with P. simplex in the Collins River at site J (35.5874, -85.6994) is a population of pleurocerids bearing shells with elevated spires, folded and transversely striate, as depicted at far left in the figure below.

This must be Isaac Lea’s Melania edgariana.  The snails bearing shells such as depicted in figure (J) below are occupying the same habitat as topotypic troostiana in East Tennessee, and all of those troostiana synonyms we reviewed in January, and topotypic perstriata in North Alabama, and all of those perstriata synonyms we reviewed in May.  In the company of P. simplex, they are grazing on the rocks of a small stream coursing down off the Cumberland Plateau.

There are two differences between edgariana of the Cumberland drainage and troostiana of the Tennessee drainage.  One is that, just as is the case with simplex, the edgariana populations of the Caney/Collins system extend much further downstream than the troostiana of East Tennessee and North Alabama.  My biological intuition suggests to me that a combination of current speed, substrate, temperature, and oxygenation is involved, such that the Caney/Collins, and many other rivers of Middle Tennessee and Kentucky, retain more of their upstream character downstream.  They look like big trout streams, not bass rivers.

In response to common environmental conditions, the shell morphology demonstrated by freshwater gastropod populations may vary together.  One of the more interesting papers to pass across my desk in recent years reports a shell morphological study conducted by Kistner and Dybdahl [6] in the Snake River of Idaho [7].  The authors demonstrated that generalized Procrustes variance in populations of the (native) Pyrgulopsis robusta and the (introduced) Potamypyrgus antipodarium varied in parallel, apparently as a function of current speed.

(J) Collins R, (I) Center Hill Lake, (H) Caney Fork
So the only other distinction between the edgariana of the Cumberland drainage and the troostiana of the Tennessee is the degree of shell costation – strong for edgariana, weak for subspecies perstriata in North Alabama, and absent for the typical subspecies in East Tennessee.  We devoted some considerable fraction of our April post to research on shell costation or plication.  Intraspecific variation in that trait has been well-documented – sometimes apparently heritable, sometimes not – but intraspecific, in any case. 

I cannot find any evidence counter to the hypothesis that Melania edgariana (Lea 1841) of the Cumberland is a junior synonym of M. troostiana (Lea 1838) of the Tennessee.  But let us save Lea’s name “edgariana” as a subspecies to describe populations of P. troostiana bearing strongly costate shells, shall we?  Again, I am duty-bound to remind my readership that we here in the FWGNA project define the term “subspecies” in its original, classical sense, and to point you to my essays of February and March, 2014, for elaboration [8].

I do not want to nominate the population of edgariana at site J as topotypic, however, since it inhabits the Collins River, and Lea specified “Cany” Fork.  So further downstream, in 1948 the US Army Corps of Engineers built Center Hill Dam near Smithville, and impounded the Caney Fork upstream 64 miles, almost to its junction with the Collins River.  Most unexpectedly, to me in any case, several pleurocerid populations, including edgariana, have survived the impoundment [9].  The shell labelled (I) in the figure above was collected during the winter draw-down from a population inhabiting the sandy shallows of Center Hill Lake at the Floating Mill Recreation Area (36.0460, -85.7620).

But again, I hate to restrict an 1841 type locality to a 1948 impoundment.  So the Caney Fork picks up again below the Center Hill Dam and flows another 25 miles to its mouth at The Cumberland River.  The shell labelled (H) in the figure above was sampled at the TN 264 bridge (36.1816, -85.9081), a spot I suggest as the type locality for Pleurocera troostiana edgariana by virtue of ease of access, as well as historical fidelity.

As Goodrich [5] suggested, Pleurocera troostiana edgariana populations seem to range widely across the Cumberland drainage of TN/KY, including the Stones, Harpeth, and Obey Rivers as well as the Caney/Collins.  And indeed, several of the larger tributaries of the Tennessee River in Middle Tennessee also host edgariana populations, including the Duck [10] and the Elk.  We depicted a specimen from the Elk River at Kelso (site “G”) last month, as a teaser for this month’s essay.

Well, I do appreciate the forbearance of my rapidly-dwindling readership as yet another soggy length of malacological tapestry has rolled off the FWGNA loom, dripping with arcana and arrogance.  Next month we’ll finish up where we started, back in Kentucky with Captain Lyon, and summarize, at long last, I promise.


Notes:

[1] These were the same publications in which Lea described the M. ebenum about which we obsessed in October, and the M. teres and M. strigosa we mentioned in January:
  • Lea, Isaac (1841) Continuation of Mr. Lea's paper on New Fresh Water and Land Shells.  Proceedings o the American Philosophical Society 2: 11 – 15.
  • Lea, Isaac (1843)  Description of New Fresh Water and Land Shells.  Transactions of the American Philosophical Society 8: 163 – 250.
[2] Tryon, G. W. (1873)  Land and Freshwater shells of North America Part IV, Strepomatidae.  Smithsonian Miscellaneous Collections 253: 1 - 435.

[3] Conrad, T.A. (1834)  New fresh water shells of the United States, with coloured illustrations, and a monograph of the genus Anculotus of Say.  Also a synopsis of the American naiades.  Judah Dobson, Philadelphia.  76 pp.

[4] For all we know about the Lea/Conrad relationship, see:
  • Isaac Lea Drives Me Nuts [5Nov19]
[5] Goodrich, C. (1940) The Pleuroceridae of the Ohio River drainage system.  Occas. Pprs. Mus. Zool. Univ. Mich., 417: 1-21.

[6] Kistner, E.J., and M.F. Dybdahl.  2014.  Parallel variation among populations in the shell morphology between sympatric native and invasive aquatic snails.  Biological Invasions  16(12):2615-2626.

[7] We devoted a significant number of column inches to the Pyrgulopsis robusta populations of the Snake River some years ago.  See:
  • Idaho Springsnail Showdown [28Apr05]
  • Idaho Springsnail Panel Report [23Dec05]
  • When pigs fly in Idaho [30Jan06]
  • FWS Finding on the Idaho Springsnail [4Oct06]
[8] Subspecies are populations of the same species in different geographic locations, with one or more distinguishing traits.  For elaboration, see:
[9]  In addition to P. troostiana edgariana, the pleurocerid species inhabiting the margins of Center Hill Reservoir include P. canaliculata, which does not surprise me, and P.laqueata alveare, which is really rather interesting.  But no, I have not seen any P. simplex in the shallows of Center Hill Lake.  Why not?  We may come back to this.

[10] According to van der Schalie (Sterkiana 52: 45 - 56), in 1931 Goodrich recorded Goniobasis edgariana way up the Duck River at Manchester.  He did not apparently find edgariana, or any pleurocerid populations that looked anything like troostiana, anywhere else in the Duck drainage.  But I am  not sure how well Goodrich surveyed the smaller tributaries.

Sunday, May 10, 2020

A House Divided

Editor’s Note – This the eighth essay in a seemingly-endless series on phenotypic variety and taxonomic confusion in the pleurocerids of the Tennessee/Cumberland.  To appreciate the arguments advanced below, you really must have read last month’s post, and it would help to have read December and January as well.

By the spring of 1862, America had reached a point of crisis.  Isaac Lea had run out of names for pleurocerid snails.

Between 1834 and 1861 Lea had described 184 species in the genus Melania, which he now wrote had become “so enormously extended as almost to prevent the possibility of finding suitable names for its species.”  So in April of 1862 Lea [1] proposed to split a large subset of Melania bearing shells with “auger-shaped” apertures into a new genus Trypanostoma.  And in May [2] he proposed to split another large subset bearing shells with “subrhomboidal” apertures into a second new genus, Goniobasis.

Lea then went on to describe 242 new pleurocerid species in 18 months, as though the pressure in some vast balloon of Latinate adjectives had suddenly been exploded by nomenclatorial pin prick.  The splatter included spinella which we reviewed in January [3] and the aterina / porrecta / vittatella / cumberlandensis clot we featured way back in August [3], sent to Lea by Captain Lyon from way down yonder in Cumberland Gap.  Also detonated onto the pages of learned journals in 1862/63 were a tremendous variety of additional nomina assigned to pleurocerid populations from throughout the Tennessee/Cumberland region, including Goniobasis gabbiana, which immediately arced into oblivion, only to be called back on this blog in 2016 [4].


Lea’s genus Trypanostoma never caught on.  George Tryon [5] considered it “unquestionably” a junior synonym of Rafinesque’s Pleurocera [6], as did Goodrich [7] and Burch [8].  But Lea’s genus Goniobasis was accepted by both Tryon and Goodrich as describing a “natural” group, hanging on until the 1980s, when Burch resurrected the zombie taxon, Elimia, to replace it.

We now understand, of course, that the distinction made by Lea in 1862 was illusory.  There is no  evolutionary difference between Trypanostoma, Pleurocera, Goniobasis or Elimia whatsoever [9].  The tragic rift that tore the pleurocerid fauna apart in 1862, setting brother against brother, would not be healed for 150 years.

Nevertheless, in 1873 George Tryon, almost certainly in direct consultation with Isaac Lea himself, divided all 184 species that Lea had described prior to the Trypanostoma/Goniobasis crisis of 1862 into either Pleurocera or Goniobasis.  In general, the larger and more heavily-shelled nomina went into the former genus and the more lightly-shelled species into the latter.  During that process, all five of the previously-described slender, striate East Tennessee species we discussed in January [3] were allocated to Goniobasis: troostiana (Lea, 1838), teres (Lea, 1841), strigosa (Lea, 1841), striatula (Lea 1841) and arachnoidea (Anthony 1854).  As well as the perstriata Lea described from North Alabama in 1852. 

So last month we reviewed the situation with Melania (now Goniobasis) perstriata, suggesting that the Huntsville-area populations described by Lea using that particular sobriquet might best be understood as a plicate subspecies of the troostiana population he described from East Tennessee way back in 1838.  We also hinted that quite a few additional names for similar populations inhabiting similar waters of North Alabama might have been described in the aftermath of  the 1862 unpleasantness [10].  Among these were pybasii (1862), paupercula (1862), crispa (1862) and decampii (1863).

Pleurocera troostiana populations, Note [21] and map below.

Lea led his 1863 description of Goniobasis pybasii [11] with “shell folded, very much drawn out,” and went to unusual lengths comparing it to four other species previously described: “reminds one of laqueata (Say),” “allied to deshaysiana but more slender [12],” “very much like grata (Anthony) [13],” and “differs from lyonii by not being striate [14].”  He did not distinguish pybasii from perstriata, nor indeed from any of his East Tennessee species, troostiana or any of the synonyms we reviewed in January.  Lea gave the habitat of Goniobasis pybasii as “Tuscumbia, Alabama, B. Pybas [15].”

Tryon [5] passed pybasii along verbatim.  Goodrich opened his 1930 treatment of G. pybasii [16] with the observation that “this species does not seem to have been collected in recent years.”  He did, however, examine nine shells (bearing poor data) then held by the Alabama museum, writing “The chief characteristic of the species is that, unlike the other plicate Goniobases of the region, it lacks the granulate spire and the usual revolving raised lines.”  He went on to broaden its range to “springs and streams of North Alabama.”  Burch [8] passed Elimia pybasii along on his page 140, unfigured.

So on March 12, after my tour of lovely Madison County, Alabama, I struck out across the rolling hills and lush farmlands toward Tuscumbia, the home of Hellen Keller, Annie Sullivan, and the first railroad on the American frontier [17].  And over the course of several days following, I was able to inventory, lightly but completely, the freshwater gastropod fauna inhabiting the springs and small streams of North Alabama.

And it materializes that pleurocerid populations bearing “shells folded, very much drawn out” that match Lea’s figure of 1863 are today widespread in the springs and small streams south of Tuscumbia.  And as a type locality for Goniobasis pybasii, I hasten to nominate what may be my favorite freshwater gastropod sampling site ever, the small spring and spring run at the foot of the Rattlesnake Saloon (Q).

My favorite sampling site, ever.
By great good fortune, the hour was getting on toward quitting time on a Wednesday evening when I pulled my pickup into the ample parking lot of the Rattlesnake Saloon, about 2 miles south of Tuscumbia.  The public establishment is located a brief stroll through verdant pastureland and a steep descent under a massive rock overhang about 20 – 30 yards above Newsom Springs.  Beer and pleurocerids on a warm Alabama evening in mid-March?  I cannot remember ever enjoying anything I have called “work” more than this.  See the example shell marked (Q) above.

Lea described Goniobasis paupercula [11] in the same 1863 article as pybasii, 11 pages later, giving the habitat simply as “North Alabama, Prof. Tuomey [18].”  His description of the “subcylindrical” shell mentions whorls “folded above and striate at the apex.” But in his remarks, he confessed that he had “not a single one with an entirely perfect apex, being usually decollate at the second whorl from the base.”  In contrast to pybasii, Lea did not compare paupercula to any other pleurocerid previously described – not to perstriata or anything else – implying, I suppose, that something in his description made paupercula self-evidently unique.  Possibly the decollation?  In any case, Tryon passed paupercula along uncritically.

Goodrich (1930) reported observations on seven populations of paupercula collected by H. H. Smith from small streams in Lauderdale and Franklin Counties, Alabama.  Goodrich’s notes on shell morphology expanded those of Lea considerably, especially with respect to variation in shell sculpture.  Burch [8] picked up the species from Goodrich (1940) and passed it along (with Tryon’s redraft of Lea’s original figure) on his page 140, giving the range simply as “creeks of Northern Alabama.”
Juvenile, 9.2 mm

My surveys through Lauderdale and Franklin Counties this March did not yield any pleurocerid populations bearing decollate shells.  But I did stumble upon a population bearing shells very nearly identical to Lea’s 1863 description and figure in Lipscomb Spring, south of Huntsville, on the opposite side of the Tennessee River (R).  The figure above shows an adult shell, the figure at left a juvenile, suggesting that Lea’s speculation about striae around the apex was correct.

Lea published a brief, Latinate description of Goniobasis decampii in 1863, which he followed with a more complete English description in 1866 [19].  The shell, he reported, was “plicate, striate below, greatly attenuated, thin.”  Lea gave the habitat as “Huntsville, Alabama; Wm. H. DeCamp, MD, surgeon United States Army [20].”

To quote Goodrich (1930) verbatim: 
“This mollusk is G. perstriata in all essentials save its nearly cylindrical shape.  Quite slender specimens of perstriata have been taken in Big Spring Creek at Huntsville… It is possible that the original collector, Dr. DeCamp, had visited some spring or creek in the vicinity of Huntsville containing these shells, and that the locality has not since been examined.  A ‘pure culture’ of decampii would warrant, of  course, its definite recognition.”
In my week of sampling springs and streams around North Alabama I did not find a single individual pleurocerid bearing a shell as “greatly attenuated, thin” as Lea’s figure suggests, much less a “pure  culture.”  Goodrich’s speculation seems quite plausible to me – that the single shell sent Lea by Dr. DeCamp was subsampled from the perstriata population of Big Spring, Huntsville, subsequently much impacted by development.

The biological and morphological considerations reviewed above combine to suggest to me that all three of these nominal species, pybasii (Lea 1862), paupercula (Lea 1862), and decampii (Lea 1863), are junior synonyms of Pleurocera troostiana perstriata (Lea 1853).  All three of these nineteenth-century taxa were defined entirely by their shell morphology.  And the shell morphology demonstrated by the example populations we have identified this month rests easily within the variance of the Huntsville-area P. troostiana perstriata populations we documented last month.

North Alabama.  See footnote [21] for locality data.
But regarding crispa (Lea 1862).  Lea described Goniobasis crispa from “Florence, Alabama; Rev. G. White” in the same 1863 paper as pybasii and paupercula, two pages after the latter [11].  Goodrich neglected it in his 1930 work but brought crispa back as a subspecies of Goniobasis perstriata in 1940 [7].  No, Goniobasis crispa is not a subspecies of perstriata, nor is it a synonym of troostiana, nor is it related to any other species we have treated this month, or at any time in recent memory.  Goniobasis crispa (Lea 1862) is entirely different.  And to quote my favorite Alabaman, “That’s all I’ve got to say about that.”

But I will say two more things about two other gastropod populations and close with one rhetorical question.  The first thing I will say is that the tributaries of the Elk River in North Alabama are inhabited by pleurocerids bearing slender, lightly-costate shells no different from any of the other Pleurocera troostiana perstriata populations we have reviewed in the last couple months.  See the example shell from Mechanic Branch at Sim Corder Mill (S) figured way up above.

And the second thing is that if one samples up the main Elk River just a short way into Tennessee, one begins to discover populations of pleurocerids bearing slender, high-spired shells elaborately ornamented with both strong striae and dramatic costae down the entire length of their shells, from apex to lip. See the example from the Elk River at Kelso (G) above.

What is the situation with Pleurocera troostiana in Middle Tennessee?  Stay tuned.

Notes:

[1] Lea, Isaac. (1862) Description of a New Genus (Trypanostoma), of the Family Melanidae, and of forty-five New Species. Proc. Acad. Sci., Phila., xiv, pp. 161 - 175.

[2] Lea, Isaac. (1862) Description of a new genus (Goniobasis) of the Family Melanidae and eighty-two new species. Proc. Acad. Nat. Sci., Phila., xiv, pp. 262-272.

[3] Here’s my entire series on Pleurocera troostiana:
  • CPP Diary: Yankees at The Gap [4Aug19]
  • On the trail of Professor Troost [6Dec19]
  • The many faces of Professor Troost [7Jan20]
  • Huntsville Hunt [15Apr20]
[4] The most convenient medium by which to review the rediscovery of Pleurocera gabbiana would be to read essays 9 - 11 in:  Dillon, R.T., Jr. (2019c) Essays on The Prosobranchs.  Freshwater Gastropods of North America, Volume 3.  FWGNA Press [html].  Or, if you’d prefer to click your way through it piecemeal:
  • The cryptic Pleurocera of Maryville [13Sept16]
  • The fat simplex of Maryville matches type [14Oct16]
  • One Goodrich missed: the skinny simplex of Maryville is Pleurocera gabbiana [14Nov16]
[5] Tryon, G. W. (1873)  Land and Freshwater shells of North America Part IV, Strepomatidae.  Smithsonian Miscellaneous Collections 253: 1 - 435.

[6] Tryon turned out to be quite wrong here.  The question of whether Lea’s Trypanostoma might indeed be a junior synonym of Rafinesque’s Pleurocera was swept up into one of the longest-running feuds in American Malacology.  See:
  • Joe Morrison and the Great Pleurocera Controversy [10Nov10]
[7] Goodrich, C. (1940) The Pleuroceridae of the Ohio River drainage system.  Occas. Pprs. Mus. Zool. Univ. Mich., 417: 1-21.

[8] 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).

[9] 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 more, see:
  • Goodbye Goniobasis, Farewell Elimia [23Mar11]
[10] Isaac Lea described several more heavily-shelled species of pleurocerid snails from North Alabama bearing elevated spires and sometimes even striations that were ultimately allocated to Trypanostoma/Pleurocera.  Among these were brumbyi (1852), striatum (1862) and currieranum (1863).  Goodrich [5] synonymized striatum (from “Florence, Alabama B. Pybas”) under canaliculata.  And it is my hypothesis that the “spring in Madison County” from which Goodrich identified the brumbyi/currierianum pair is Brahan Spring in Huntsville (34.7062, -86.6003), in which case, that pair of specific nomina appear to be junior synonyms of Pleurocera canaliculata as well, subspecies pyrenellum.


[11] Lea described paupercula, pybasii and crispa in brief, Latinate form in his 1862 PANSP paper cited at note [2].  They were figured and described more completely in English the next year, in:
Lea, Isaac (1863) New Melanidae of the United States.  Journal of the Academy of Natural Sciences of Philadelphia 5: 217 – 356.

[12] Lea’s deshaysiana of 1841/42 (habitat “Tennessee”) was synonymized under laqueata (Say1829) by Goodrich [7, 16].

[13] Anthony’s 1860 grata (habitat: “Alabama”) has been buried by the sands of time.  Rest in peace.

[14] Put a bookmark here.  We will return to the Goniobasis lyonii populations of Kentucky in a couple months.

[15] About the life of Mr. Pybas I have found nothing.  Otherwise, Tuscumbia’s Oakwood Cemetery is the final resting place of one Mr. Benjamin Pybas, d1883 aged 76 years.

[16] Goodrich, C. (1930)  Goniobases of the vicinity of Muscle Shoals.  Occasional Papers of the Museum of Zoology, University of Michigan 209: 1 – 25.

[17] In 1834 local merchants completed a railroad from Decatur to Tuscumbia to bypass the 43-mile Muscle Shoals of the Tennessee River.  This line was incorporated into the Memphis & Charleston Railroad in 1850, ultimately becoming the first connection between Alabama and The East.  Cotton was, of course, the primary motivation for the construction of these commercial arteries.  The conduct of freshwater gastropods to Philadelphia was apparently an afterthought.

[18] Michael Tuomey (1805 – 1857), professor of geology at the University of Alabama, appointed first state geologist of Alabama in 1848, working out of Tuscaloosa, travelling broadly.

[19] Brief, Latinate description of Goniobasis decampii:
Lea, Isaac (1863) Descriptions of fourteen new species of Melanidae and one Paludina.  Proceedings of the Academy of Natural Sciences of Philadelphia 15: 154 – 156.
English description with figure:
1866. Lea, Isaac.  New Unionidae, Melanidae, etc. chiefly of the United States.  Journal of the Academy of Natural Sciences of Philadelphia (New Series) 6: 113 – 187.

[20] Dr. William H. DeCamp (1825 – 1898), originally from New York, removed to Grand Rapids in 1854, served as a surgeon in the First Michigan Engineers and Mechanics Regiment 1861 – 64.  He resumed practice in Grand Rapids and was ultimately elected to the presidency of the Michigan State Medical Society.

[21] Pleurocera troostiana populations referenced in this essay:
  • Q = Newsom Springs at the Rattlesnake Saloon. 34.6481, -87.9076
  • R = Lipscomb Spring. 34.5241, -86.6013
  • S = Mechanic Branch at Sim Corder Mill.  34.9364, -87.1314
  • G = Elk River 2 km N of Kelso. 35.1395, -86.4484

Wednesday, April 15, 2020

Huntsville Hunt

Editor’s Note – After a couple months of digression into other topics, today we return to phenotypic variety and taxonomic chaos in the pleurocerid fauna of the Tennessee/Cumberland.  I have written six essays in the series thus far, from August 2019 to January 2020.  But I’d especially recommend that you review my December and January posts on P. troostiana before going forward.

Variation in the number and strength of shell plicae (or costae), those little scallop-shaped folds wrapped around the whorls of diverse gastropods worldwide, no different from variance in every other character of the phenotype of every other creature that walks, creeps, swims or flies on this earth, has both genetic and environmental components [1].  It is always important to remember both.

Calvin Goodrich dedicated Number III in his “Studies of the gastropod family Pleuroceridae” to the phenomenon of shell plication in 1934 [2].  He documented variation in an impressive list of 21 species of Goniobasis, including G. arachnoidea (a junior synonym of troostiana), generally correlating plicate shell sculpture with upstream/downstream environmental gradients or with broadly-regional pattern. 

Misako Urabe [3] reported evidence that the strength of the shell costation (plication) developed by sibships of Korean Semisulcospira was a function both of the phenotype of the mother and the coarseness of the substrate upon which her offspring were raised, sand promoting costation more than cobble.  Taking inspiration from the work of both Goodrich and Urabe, I have argued that populations of Pleurocera catenaria from Atlantic drainages of The Carolinas varying dramatically in their shell plication be accorded subspecific status, regardless of the origin of the trait [4].
 
Melania perstriata [7]
In any case, none of the populations of P. troostiana we discussed in January, under any synonym of that species, bore plicate/costate shells, under any synonym of that shell character.  Nor indeed, does any population of any pleurocerid species anywhere in East Tennessee demonstrate any shell plication whatsoever [5].  If you set off on a voyage down the Tennessee River from headwaters in Virginia to heart in Alabama, you would pass thousands of populations of pleurocerid snails, comprising 16 species.  But the first plications you would see on the shell of any pleurocerid waving at you as you passed would pop up around the westward bend of the river at Chattanooga, where its dip begins into North Alabama.  Those would be the easternmost populations of Pleurocera laqueata [6], a chunky-shelled inhabitant of small rivers and mid-sized streams, widespread in Middle Tennessee but strangely absent further eastward.

And for some reason – perhaps regional substrate – the pleurocerid populations bearing slender, striate shells inhabiting the smallest tributaries of the Tennessee west of Chattanooga also begin to demonstrate plication, only where their range overlaps the characteristically-plicate P. laqueata.

So in 1853 Isaac Lea described and figured a pleurocerid from Alabama which he called Melania perstriata [7].  He focused on its striate shell, acutely conical with elevated spire, drawing no distinction between his new species and any of the pleurocerid species bearing striate shells and elevated spires he had previously described in East Tennessee.  Indeed, he observed that his new perstriata was “strongly allied” to his striatula (1841/43), which we discussed in January.  Although Lea did not mention any plication on the shell of perstriata in his description, his figure (reproduced above) shows light but distinct plicae on the upper whorls.

Lea gave the habitat of his Melania perstriata as “Coosa River, Alabama, Prof. Brumby.  Huntsville, Tenn., Mr. J. Clark.”  I feel certain that Lea meant Huntsville, Alabama, not Huntsville, Tennessee, for reasons that will become obvious shortly.  Tryon [8] passed Lea’s figure and description along uncritically as “Goniobasis” perstriata.

One of Calvin Goodrich’s best least-known works was his (1930) “Goniobases of the vicinity of Muscle Shoals” [9], by which he meant North Alabama, generally.  Here are the first two sentences of that important contribution: 
“Nine species and two subspecies of Goniobasis are recognized in this paper as inhabiting the vicinity of Muscle Shoals, Alabama.  I have not had the heart to count the names it has been thought necessary to throw into synonymy, always a slough of despond in the case of the Pleuroceridae.” 
Amen, Brother Calvin!  That second sentence could summarize much of my professional career.

Goodrich began his treatment of Goniobasis perstriata with several paragraphs of detailed observations on the shell morphology of the population inhabiting Big Spring Creek in Huntsville, which he said is “apparently the type locality.”  I am confident that Goodrich was correct about this.  The “Mr. J. Clark” credited by Isaac Lea for the type collection was quite likely a gentleman named Joseph Clark, the President of Huntsville, Alabama from 1844 to 1849.  And where else would the President of Huntsville collect shells to pack off to the Eastern Scientific Establishment than the large and impressive spring around which his city was built, the historic site of one of the earliest waterworks in America?
Goodrich’s observations on the “average specimen” from Big Spring Creek [10] matched Lea’s description and figure very well, focusing on the “slender, delicate” shell with striking sculpture consisting of “low plicae crossed by strong revolving lines.  The plicae disappear on the spire and the striae continue to the base.”  But to my eye, the most intriguing of Goodrich’s observations about the Big Spring Creek population are not about the “average specimen,” but rather: 
“A study of the variation of perstriata takes one so far afield that some of the original characteristics seem altogether lost and to be replaced with new features.  In Big Spring Creek there have been taken specimens that are only microscopically striate, some that show no plicae and others that are smooth and shining upon the last whorl.” 
Ten years later, based on his observations of the North Alabama pleurocerid fauna generally, Goodrich [12] dropped Lea’s “Coosa River” suggestion and expanded Lea’s “Huntsville” suggestion to “Springs and small streams of North Alabama.”  He then recognized three subspecies, all from Alabama tributaries of the Tennessee River: the typical G. perstriata perstriata (Lea 1853), G. perstriata crispa (Lea 1862), and G. perstriata decampii (Lea 1863). 

“Elimia” perstriata was accorded “Priority 1” conservation concern in the state of Alabama by Garner and Johnson in the big 2017 review volume edited by Shelton-Nix [13].  As a locality Garner & Johnson suggested, “Extant only in a few streams in Madison and Lawrence counties.”  Yes, modern-day Huntsville does indeed sprawl across much of modern-day Madison County.
Madison Co, AL. See note [15] for locality data
So on Monday morning March 9 I launched an expedition to North Alabama, resolving to visit as broad a sample of springs, streams, and small tributaries of the Tennessee drainage across the ten-county region as practically possible, focusing especially upon the environs of Huntsville.  I had mighty good weather as a general thing, and nothing ever happened to me at all [14].

And on Tuesday and Wednesday I was able to document six populations of pleurocerids under the bridges of Madison County, Alabama [15], in both rural and urban settings, bearing shells “acutely conical with elevated spire,” varying rather strikingly in both their striation and their plication, as figured below.  The shells most closely matching Lea’s (1853) figure were indeed borne by the population inhabiting the waters of the Big Spring of Huntsville, marked (P) on the map above.

Today the Huntsville Big Spring emerges from the rocky face of a small hill in the middle of the city and runs about a half-mile through a recently-renovated park to join Pinhook Creek.  The first couple-hundred yards of the stream are somewhat green and shady; the remainder of the course is entroughed in massive concrete bulkheads, thoroughly urbanized, and infested with gigantic koi of elaborate morphology and voracious habit.  But right at the mouth of Big Spring Creek, where it cascades down to join Pinhook Creek, I found a population of pleurocerids inhabiting what I here offer as the type locality of Melania perstriata (Lea 1853).

Madison County P. troostiana populations [15]
The shells borne by the perstriata population at its type locality (P) are entirely striated, bearing light but distinct plicae that tend to become obsolete with growth.  That is generally true upstream in Pinhook Creek (V) and at Ashburn Spring south of Huntsville (Z) as well.  But the shells borne by populations in the Flint River (W) and at Burns Spring east of Huntsville (Y) are only weakly striate or plicate, on the upper whorls alone.  And in Limestone Creek (U) no striation nor plication is detectable on the shells whatsoever.  To borrow Goodrich’s poetic imagery, they were “smooth and shining upon the last whorl.”  Compare Limestone Creek shell morphology with that demonstrated by the P. troostiana population inhabiting Gap Creek, which kicked off this long series way back in August of 2019 [16].

I cannot find any biological evidence counter to the hypothesis that perstriata (Lea 1853) is a junior synonym of troostiana (Lea 1838).  But let’s save perstriata at the subspecific level to describe lightly-plicate/costate populations of Pleurocera troostiana, shall we?  Remember that we have defined the word “subspecies” to mean “populations of the same species in different geographic locations, with one or more distinguishing traits.”  Those words mean exactly what they say, nothing less and certainly nothing more [4].  The relationship between typical troostiana and its subspecies perstriata in Alabama is the same as that between typical catenaria and its subspecies dislocata in the Carolinas.  The FWGNA database will show that sites P, V, W, Y and Z are inhabited by Pleurocera troostiana perstriata, and while site U hosts typical P. troostiana troostiana.

So what about those other species that Goodrich shifted underneath perstriata, Lea’s crispa of 1862 and decampii of 1863?  Indeed, weren’t doctors, lawyers, and Indian chiefs from all over small-town America, spurred by nineteenth-century civic pride, plucking gastropods from their local springs and packing them off to the great Isaac Lea in Philadelphia?  Why yes, they were.

But storm clouds were gathering over the fertile fields of American malacology.  In our next installment... Crisis!


Notes:

[1] For an in-depth review of the heritability of shell morphology, albeit in pulmonates, see:
  • The heritability of shell morphology in Physa h^2 = 0.819! [15Apr15]
[2] Goodrich, C. (1934)  Studies of the gastropod family Pleuroceridae – III.  Occasional Papers of the Museum of Zoology, University of Michigan 300: 1 – 11.

[3] Urabe, M. 2000. Phenotypic modulation by the substratum of shell sculpture in Semisulcospira reiniana (Prosobranchia: Pleuroceridae). J. Moll. Stud. 66: 53-59.  For more, see:
  • Semisulcospira research: A message from The East [6Jan08]
  • Semisulcospira II: A second message from The East [1Feb08]
[4] To refresh your memory on the situation with Pleurocera catenaria dislocata, and the concept of the subspecies as we use it in the FWGNA project, See:
  • What is a subspecies [4Feb14]
  • What subspecies are not [5Mar14]
[5]  Here’s a memo from the FWGNA Exception-that-Proves-the-Rule Department.  To be absolutely complete, we should note that the shells of the pleurocerid population inhabiting the Hiwassee River as it flows northwest down the mountains of East Tennessee do in fact bear dramatic costations.  This is actually a trans-Appalachian population of the Atlantic-drainage species Pleurocera catenaria.

[6] The degree of costation also varies dramatically along an upstream/downstream gradient in populations of Pleurocera laqueata as well.  See:
  • Pleurocera alveare: Another case of CPP? [8Aug18]
[7]  Melania perstriata was listed without description by Lea in 1852 (Proceedings of the American Philosophical Society Volume 5, page 252).  The species was formally described and figured the next year:
Lea, Isaac (1853)  Description of a new genus (Basistoma) of the Family Melaniana, together with some new species of American Melaniae.  Transactions of the American Philosophical Society (new series) 10: 295 – 302.

[8] Tryon, G. W. (1873)  Land and Freshwater shells of North America Part IV, Strepomatidae.  Smithsonian Miscellaneous Collections 253: 1 - 435.  For more about the relationship between Lea and Tryon, see:
  • Isaac Lea drives me nuts [5Nov19]
[9] Goodrich, C. (1930)  Goniobases of the vicinity of Muscle Shoals.  Occasional Papers of the Museum of Zoology, University of Michigan 209: 1 – 25.

[10] Goodrich’s observations were based both on the extensive collections of Dr. Bryant Walker [11] and on those of the Alabama Museum of Natural History.  He especially thanked “Mrs. Herbert H. Smith who made the selection of shells of the Alabama Museum, packed and dispatched them.”

[11] Walker’s collection was donated to the University of Michigan in 1936.  For a tribute, see:
  • Bryant Walker’s Sense of Fairness [9Nov12]
[12] Goodrich, C. (1940) The Pleuroceridae of the Ohio River drainage system.  Occasional Papers of the Museum of Zoology, University of Michigan  417: 1-21.

[13] Garner, J.T. & P. Johnson (2017) Freshwater Snails (Gastropods).  pp 7 – 42 in Shelton-Nix, E. (ed) Alabama Wildlife, Volume 5. The University of Alabama Press, Tuscaloosa. 355 pp.

[14] A tip of the straw hat to Huckleberry Finn, Chapter 12.

[15] Pleurocera troostiana populations in Madison County, AL:
  • P = Type locality of M. perstriata. Big Spring outfall, Huntsville 34.7246, -86.5915
  • U = Limestone Ck.  34.9199, -86.7645
  • V = Pinhook Ck. 34.7752, -86.5915
  • W = Flint R.  34.8228, -86.4832
  • Y = Burns Spring  34.7696, -86.4258
  • Z = Ashburn Spring  34.5249, -86.5132
[16] For a quick refresher on phenotypic plasticity in P. troostiana:
  • CPP Diary: Yankees at The Gap [4Aug19]

Monday, April 13, 2020

A stultifyingly boring review...


I heard  a lot of nice comments about my online presentation to the Charleston Natural History Society Wednesday evening.  Several of you asked if the event might be available for later viewing.

Alas, it doesn't look as though my handsome face and cheery commentary were archived anywhere.  But I have uploaded a pdf version of the powerpoint presentation I offered that evening on the FWGNA site, here:

The Freshwater Gastropods of South Carolina [pdf, 6.9 mb]

Abstract:  Founded In 1998, the Freshwater Gastropods of North America Project is the largest-scale inventory of any element of the macrobenthos ever conducted in the United States. At present the survey extends over all or part of 15 states, including the Atlantic drainages from Georgia to the New York line, Ohio drainages above the mouth of the Cumberland, and Tennessee drainages above Chattanooga. For the 113 species of freshwater snails inhabiting this vast region we have developed dichotomous keys, range maps, figures, ecological notes and an overall rank-abundance tabulation.

The first state surveyed by the FWGNA Project was South Carolina. The rivers, streams, swamps, ponds and reservoirs of The Palmetto State host a fauna of 35 freshwater gastropod species, 19 prosobranchs (bearing gills) and 16 pulmonates (bearing lungs). Almost all are tiny, brown, and obscure. None are endangered, commercially important, useful in any way, or indeed even interesting. Three are exotic invasives, and another five (apparently) domestic invasives, but of no consequence. Bring clothespins for your eyelids, folks – this one’s a real snoozer.

Wednesday, April 8, 2020

Freshwater Gastropods Tonight!


Here’s your chance to see history in the making!  This evening at 6:30 PM (EDT) yours truly will offer the first-ever online presentation to The Charleston Natural History (Audubon) Society, “The Freshwater Gastropods of South Carolina: A stultifyingly boring review of a justifiably obscure fauna.”  This will also be the first-ever online presentation yours truly has ever offered.  What could go wrong?

The public is cordially invited!  You’ll need to download a little bit of software from the “Go To Meeting” website onto your computer, tablet, or smartphone, here:

Then at 6:30, hit this link…
https://global.gotomeeting.com/join/263942469

You can also dial in using your phone, here…
United States (Toll Free): 1 877 309 2073
United States: +1 (646) 749-3129
… And in any case, enter this access code: 263-942-469.
We look forward to seeing you all this evening!

Monday, March 16, 2020

Is Marstonia ozarkensis extinct?

Editor’s Note – This is the second of a two-part series on an enigmatic hydrobiid with a last known address in northern Arkansas.  You really should go back and read my essay of 10Feb20 before proceeding through this month’s essay, if you haven’t already.

When last we left our fearless jpeg naturalist, he had just received several images of hydrobiid snails from Ms. Rachel Vinsel, the curatorial assistant at the Illinois Natural History Survey.  One image depicted cotypic Marstonia ozarkensis, collected by A. A. Hinkley in 1914 from the White River drainage in northern Arkansas [1], declared extinct by the US Fish & Wildlife Service in late 2018 [2].  That’s the first image in the photomontage below, reprinted from last month’s essay.

Ah, but there were “several images” attached to Rachel’s late February email.  She went on to add: 
“While I have you, I was wondering if you'd mind taking a look at image 0097 as well? This one was collected in the Kishwaukee River (Rock River Dr.) Winnebago Co., IL. It's not quite 3mm tall.” 
 Rachel’s image 0097 is labelled “Kishwaukee unknown,” second from left below:

All four approx 3 mm standard length
Holy crap, we have seen those little snails before.  At this point, could I ask you all to indulge me?  Would you mind opening up my essay of 19Jan16 in a new window?  Here’s the link:

In that charmingly-befuddled essay, you may remember my fumbling with a mysterious population of 3 mm hydrobiid snails collected from the muck of Lake St. Clair, 25 miles east of Detroit.  Check out the photos in that essay, one of which has been clipped and inserted third in the montage above.  And now could I ask you to refer to my follow-up essay of 5Feb16:

The matches between cotypic M. ozarkensis, Rachel’s Kishwaukee unknown and the Lake St Clair Marstonia letsoni is pretty darn near perfect, am I right?  And let me add yet another observation. 

In January of 2017 I was combing through a remarkable set of collections made by our good friend Ryan Evans up in Kentucky, when my eyes fell on a single, tiny shell from Elkhorn Creek, about 10 km north of Frankfort.  That shell is depicted at the far right of the montage above.  That’s pretty good match as well, am I right?

So we have now established two things.  In 2016, we demonstrated that populations of Marstonia letsoni are quite literally obscure – tiny snails, inhabiting dark recesses, sometimes in deep water.  To find one, you’d need to be more persistent or more lucky than I, your humble correspondent, who has never seen one in his entire 45-year career combing the lakes and rivers of America, overtly and deliberately committing premeditated acts of freshwater malacology in the first degree.

And we have now documented that Marstonia letsoni has a strikingly broad range.  Lake St Clair is 500 km north of Frankfort, KY, and 500 km east of the Kishwaukee River at Rockford, IL.  Could Marstonia letsoni range another 700 km to the Ozarks?  Might Marstonia ozarkensis (Hinkley 1915) be a junior synonym of Marstonia letsoni (Walker 1901)?

Let me make one final point in closing.  All authors who have any first-hand experience in this arcane little corner of malacology – Hinkley, Bob Hershler [3], and Shi-Kuei Wu [4] – have been unanimous that in overall morphology and life habit, both Marstonia ozarkensis and M. letsoni are very similar to a third species, Marstonia scalariformis.  The primary distinction is a carina or keel on the shell of scalariformis, which Wu and colleagues [4] observe “may be absent or only vaguely apparent” in some natural populations.  See Wu’s Figures 26 – 29 below.

M. ozarkensis (26, 27) and M. scalariformis (28, 29) from Wu [4].
Marstonia scalariformis rivals M. letsoni in both obscurity of life habit and vastness of range.  Wolf [5] described “Pyrgula” scalariformis in 1869 from a single shell found by the banks of the Illinois River.  Hinkley [6] described wabashensis from the Wabash River at the Illinois/Indiana border in 1908, which Hershler [3] synonymized under scalariformis in 1994, noting “variable carina development.”  Hershler’s figure of the penial morphology of scalariformis sampled from the Meramec River in Missouri shows bifurcation reminiscent of the letsoni penis figured by Berry [7].

And the “very incompletely known” range of scalariformis ranges all the way from central Illinois south down to tributaries of the Tennessee River in north Alabama [8].

Hinkley thought that the previously-described species most similar to his ozarkensis was wabashensis.   Hershler agreed, suggesting that wabashensis was a junior synonym of scalariformis and adding further that letsoni was also most similar to scalariformis, without directly comparing ozarkensis to letsoni.  I am not sure here today whether Marstonia ozarkensis (Hinkley 1915) is actually extinct, or if it was simply a local population of what has been called elsewhere letsoni (Walker 1901), or wabashensis (Hinkley 1908) or possibly even scalariformis (Wolf 1869), now here in the 21st century misunderstood into oblivion.


Notes:

[1] Hinkley, A.A. (1915) New Fresh-water Shells from the Ozark Mountains. Proceedings of the United States National Museum, 49:587-589.  This is actually the 1916 volume of the PUSNM, but Hinkley’s date of publication is given as “December 23, 1915” in the index.

[2] USFWS 2018.  Ozark snail species presumed extinct following science-based surveys.

[3] Hershler, R. (1994) A review of the North American freshwater snail genus Pyrgulopsis (Hydrobiidae).  Smithsonian Contributions to Zoology 554: 1-115.

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

[5] Wolf, J.  (1869) Descriptions of three new species of shells.  American Journal of Conchology 5: 198.

[6] Hinkley, A. A. 1908. A new species of Pyrgulopsis. Nautilus 21: 117-118.

[7] Berry, E. G. (1943)  The Amnicolidae of Michigan: Distribution, ecology, and taxonomy.  Misc. Publ. Mus. Zool. Univ. Mich. 57: 1 – 68.

[8] Walker, B. 1906. New and Little Known Species of Amnicolidae. Nautilus, 19:114-117.  Walker identified the population collected by Mr. Hinkley near Florence, Alabama, as “Pyrgulopsis mississippiensis (Pilsbry),” which is a junior synonym of M. scalariformis, according to Hershler [3]. There are also museum records of M. scalariformis from the Flint River near Huntsville that need confirmation.