Art, science, and public policy: A dialogue in three languages

I have a lot of friends and family who enjoy travel, and spend a substantial amount of time and money doing it, and imagine that their hobby returns some sort of profit to the intellect or character.  Isn’t travel broadening?  Don’t we learn from exposure to new lands, new cultures, new value systems, new ways of looking at the world?  Yes, of course.  But I found countless worldviews, cultures, and value systems trumpeted in the morning headlines at the end of my driveway this morning, ripe for engagement in the aisles of the grocery store across the street this afternoon.  No further travel is required.

As my loyal readership will attest, I have long been fascinated by the diversity of worldviews I encounter in my workday life, and the relationships between them.  The index item at the right of your screen labeled “Worldview Collision” will link to eight essays on the subject when I push the “submit” button on the present post.

The majority of my seven previous essays have explored the relationship between the worldview of science and the worldview of law or public policy, among the most common of the culture clashes in my experience. To understand their proper relationship I have adapted an analogy I first developed about twenty years ago during the height of the most recent creation/evolution controversies between science and religious faith.  Scientists play baseball, lawmakers and regulatory agencies play banjo.  Those worldviews are not incompatible, in the sense that my father was both a banjo picker and a catcher.  But not compatible, either.  Nobody ever tries to integrate one with the other. 

I favor the baseball/banjo analogy because most of my colleagues in the world of science seem to have a better grasp on the proper relationship between sports and art than between science and anything else, possibly because we are more objective.  We don’t write grant proposals to shortstops, nor debate fiddlers over the 10th grade biology curriculum.

 

Indeed, I rarely interact with artists in my professional life [1].  Thus, an email I received this past August (18Aug25) from one Ms. Julia Galloway [2] fell upon my eye as dew drops from heaven.  She introduced herself as: 

“… a professor and ceramic artist based in Montana. I’m currently working on a project focused on raising awareness about endangered species. For this project, I am creating ceramic urns to represent each threatened, endangered, recovered, and extinct species in the U.S. The project will culminate in the creation of approximately 1,200 urns, with completion expected by 2027.”

Ms. Galloway went on to explain that she had created “400+” urns as of that mid-August date and had (apparently) worked down from the California Condors to the freshwater gastropods, finding her supple hands now poised over a throw of clay to be entitled, “Anthony’s Riversnail.”  And googling about the internet for inspiration, she had found my “fabulous photo” posted on the FWGNA site.  And requested permission to use.

 

How fascinating!  The concept of “endangerment” is purely a matter of law, of course, and “raising awareness” a political objective.  Here an artist addresses a scientist over a matter of public policy. A conjunction of three worlds.

 

On 21Aug25 I replied to Ms. Galloway certifying, as I always do, that all of the images on the FWGNA site are freely available for anybody to use for any purpose whatsoever, and offering to help her in any other way I could.  And I concluded, doing my best to address her in her native tongue: 

“Notice that there's a photo of Leptoxis crassa (“Anthony’s Riversnail”) in situ at the bottom of (the species) page [here].  Which brings me to my final point.  Bless your heart!  These things are brown bumps on a rock.  God made them by throwing little balls of clay at dirt.  If you can make art out of Leptoxis crassa, my cap's off to you.”

 And to the bottom of my email of 21Aug25 I added, “PS – 1,200 urns? Are you nuts?”

Brown bumps in Limestone Creek, AL.

Here the challenge of communication across cultures was on full display.  At no point in her initial email to me, nor indeed in any of her subsequent correspondence, did Ms. Galloway mention the rich symbolism just below the surface of her artwork.  Her urns are modeled after the funerary urns of ancient Egypt.  But, quoting from her website, “displayed empty as a sign of hope.”  Anthony’s Riversnail may be on its sickbed, by this metaphor, but it ain’t dead yet.

 

Ms. Galloway replied immediately thanking me for my “delightful and thoughtful reply,” confessed that she does feel a little bit nuts at times, and asked me if I would like to see images of the urn upon completion. And I responded immediately in the affirmative, and suggesting that she just “throw a couple balls of clay at a flowerpot” to expedite the process.

 

I was tremendously impressed to receive the set of three jpegs below on the afternoon of 22Aug25, less than 24 hours after I had granted Ms. Galloway permission to use FWGNA imagery.  Maybe I shouldn’t have been so surprised – with 400 urns down and 800 to go, she must be nothing if not efficient.  Three individual snails were depicted various faces of the Anthony’s Riversnail urn, one snail crawling to the left (a) and two crawling to the right (b, c), as from the vantage point of a wary stonefly.  None of these images was modeled, as far as I could tell, from anything on the FWGNA site.  At least overtly.

 

Although starkly beautiful in their execution, I immediately noticed a couple significant technical problems with this urn.  Or at least, they seemed significant to me.  So on 23Aug25 I addressed my third email to Ms. Galloway.

And this time, I felt compelled to speak a little bit of science.  I began with some background on gastropod coiling, so as to introduce the adjectives “sinistral and dextral,” and noted that no case of sinistrality has ever been documented in the Pleuroceridae, as far as I know.  I then wrote:

“You have depicted three individual snails on your urn, am I correct?  The images of which you labeled on the jpegs you sent me yesterday afternoon AO22-a, AO22-b, and AO22-c, yes?  Snail (b) is bearing a dextral shell, correct as you have sculpted.  But snail (a) and snail (c) are bearing sinistral shells.  Not only is that uncomfortable to my eyes, it is unscientific.”

That seemed harsh.  So I added, to soften the blow:

“Perhaps you were working from (somebody else's) closeup photograph of a pleurocerid animal, reversed in some popular publication or on the internet?   Amateurs often publish reversed images, careless of the difference.  In fact, it seems highly unlikely to me that anybody other than a professional malacologist would ever notice the chirality of the snails you have sculpted on your urn.  So if you want to let it go (as Queen Elsa would suggest) I would certainly understand.”

Well, a couple weeks passed.  And I honestly did not think I would ever hear from Ms. Galloway again.  At the rate of one urn per 24 hours, I imagined that she must be well into the unionid mussels by that point, gastropods let go, gone, and forgotten.  But on 2Sept25, I was most pleased to receive yet another lovely communication from my artist-pen-pal:

“Thank you so much for bringing chirality to my attention! I loved reading your email and learning more about gastropods. It's always a treat when I get to hear someone talk passionately about their field of study (especially when they're brown bumps on a rock).

 

Sometimes species have very few images, which was the case with this species. Not knowing about chirality, I flipped some of the images to give myself more viewing angles and compositional options. Now that I know about how snail shells grow, I would like to remake the urn. Would you happen to have any additional images of Anthony's River Snail that you could share?

 

Thank you again for taking the time to share this information with me and for your support! Take care and I hope to hear from you again soon!”

Well no, I myself did not have any additional photos of L. crassa showing anything that the couple images already posted on the FWGNA species page did not.  But on a whim, I executed simple a google-image search on “Athearnia anthonyi” and landed, of course, on the Wikipedia page [3].  And good grief.  The image at the top of the Wikipedia page is sinistral!

Wikipedia. From Dick Biggins, USFWS.

So on the evening of 4Sept25 I addressed my fourth email message to Ms. Galloway, apologizing on behalf of the entire profession of freshwater malacology, re-assuring her that Dick Biggins (the donor of the photo) is a careful worker and confessing that I could not imagine that he himself would upload a mirror-reversed image.  But regardless of how the error occurred, I was sorry that some member of our extended community had not fixed it by now.  Not it.

 

I then suggested three remedies: (1) Sculpt the Wikipedia image from a mirror, (2) Adjust the Wikipedia image using the Photoshop mirror-image-reverse button, or (3) model from some other pleurocerid. Honestly, at the resolution of a funerary urn, all pleurocerid bodies are indistinguishable.  I sent her a good image of some other pleurocerid individual crawling to the viewer’s right, so that she would have both left-travelling dextral and right-travelling dextral models to work from.

 

And on 7Sept25 Ms. Galloway thanked me once again, and asked me if I would like to see images of “the new and improved urn when it is completed?”  To which I replied in the affirmative.  But I never heard from her again.  And that’s OK.

 

The philosopher Ian Barbour (1923 – 2013) has suggested [4] that there are four ways in which worldviews might relate: (1) independence, (2) dialogue, (3) conflict and (4) compatibility.  Independence is the unexamined status quo, compatibility a pipe dream, and conflict is right out.  I love, love, love dialogue.

 

The relationship I have demonstrated above is (2) a dialogue between the worldview of science and the worldview of art.  One might subclassify it as (2a) science helps art.  Ms. Galloway asked me to help her.  I did everything I could to do so.

 

Science and art are not incompatible, here obviously.  But mark me well.  Science and art are not compatible either.  They are very simply, and very profoundly, different.  Ms. Galloway is an artist, and she took the lead in this interaction, and I (a scientist) did what I could to help her create a work of art, and at no point did anything that happened between us during our entire two-week interaction have anything to do with science whatsoever.  The pleurocerid images she carved into that pot could bear sinistral shells, or dextral shells, or polka-dot shells, it does not matter.  And in fact, she never asked me for any of the free advice I offered her at any point, and in retrospect, I may have been interfering with the creative process, and if I ever hear from her again, I will apologize for butting in.

 

But I can’t help it, I love that sort of thing. The proper relationship between our worldviews is one of dialogue.  A dialogue with a fine artist is like an expedition into the bush with a Hottentot, from the seat of my own kitchen table.

 

And here is the most interesting thing about my two-week dialogue with Ms. Galloway.  This particular artist’s motivation was not artistic, but political. 

 

The Oxford Dictionary defines art as “an expression of human skill producing works to be appreciated primarily for their beauty or emotional power.”  But to quote from Ms. Galloway’s website, she considers her work “a catalyst for social change.” 

 

She selected Anthony’s Riversnail as one of her 1,200 subjects because that particular gastropod was entered onto the Federal Endangered Species list on April 15, 1994, see 59 FR 17994-17998 [5]. And “By creating an urn for each (such) species, (she) is making (rarely-seen) species visible, and through this awareness, compassionate action is possible.”  In other words, Ms. Galloway apparently thinks that the worldview of art and the worldview of politics are compatible, such that the former can influence the latter.

 

Bless her heart.  You will have by now noticed that no representative from the world of politics or public policy has entered into the chat room with the artist and the scientist to this point in my essay, nor will one subsequently appear.  I myself was awarded a AAAS Congressional fellowship many years ago, and learned just enough of the language spoken on Capitol Hill 1981 – 82 to appreciate my limitations.  And I do know quite a few hardworking biologists employed by natural resource agencies, both state and federal. And speaking now for all the legislative bodies and all the regulatory agencies and all the departments of natural resource management involved in all the endangered species conservation nationwide, as well as the entire [6] gastropod fauna of Limestone Creek, Madison County, Alabama, thanks for the pot.  Not a great likeness, but it’s lovely, dear, it really is.

Dave Michaelson & Randy Sarver

Art and Public Policy have different languages, different cultures, different values, and different ways of looking at the world. That they are not incompatible is witnessed by Ms. Galloway herself, who is both an artist and a social activist.  But the worldviews are not compatible, either.  Neither art nor public policy can affect the other, any more than the marching band affects the halftime score, or the halftime score the marching band.

 

But lest we condescend.  Of all the holders of all the worldviews of all the world – Art, Science, Business, Finance, Law, Medicine, Engineering, Religious Faith, Harry Potter, or Star Trek, we scientists are the most arrogant.  The notion of science-based public policy is just as absurd as pottery-based public policy, and none of us seems to realize it.

 

On the morning of 4Sept25, the same day I was to send my fourth email to Ms. Galloway, I met my good friend Randy Sarver in the parking lot of the Missouri Department of Natural Resources, Jefferson City. Randy is an excellent biologist, and we have developed a warm relationship over many years, and he helped me unload four flats of empty black-capped vials that used to hold macrobenthic samples collected by the MoDNR 2015 - 2017, and swap them for a fresh batch of MoDNR macrobenthic samples 2017 - 2018. 

 

I am sure that Randy and Dave Michaelson and all our friends at the MoDNR do a great job monitoring the water quality of the Show-Me State, and I would never dream of offering them any advice whatsoever, because I can’t, any more than they would dream of offering me any advice about malacology, because they can’t.  Randy and I are in dialogue.  That’s the thing I love.

 

Notes:

 

[1] I actually did post one previous essay on the relationship between science and art, way back in 2011:

• When Science and Art Collide [4Feb11]

 [2] Learn more about Ms. Galloway from her lavish web presence:

• Julia Galloway [home]
• Endangered Species Project [direct]
• Wikipedia [page]

 [3] Wikipedia, accessed 10Dec25 [link]

 

[4] Here I am generalizing Barbour’s thought on the science – religion relationship to the relationship between worldviews of any sort.  His “fourfold typology” was most clearly stated in:

• Barbour, I. G. (2000) When Science Meets Religion: Enemies, Strangers, or Partners?  Harper, 205 pp.

[5] For the Democrats among my readership, who imagine that findings such as those published in the Federal Register on 15Apr94 have anything to do with science whatsoever, please refresh your memory with the ten essays I have written on the Snake River Physa scandal to date.  Actually, you could skip the first six, if you want, and go straight to:

• The SRALP and the SRNLP: A new hope [14May24]
• The SRALP and the SRNLP: Physa acuta were found [11June24]
• The Twelve Phascinating Physa of Bliss [2July24]
• Cytoplasmic Male Sterility in the Snake River Physa [7Aug24]

[6] Fourteen species comprise the exuberant gastropod fauna of Limestone Creek: four pleurocerids, three hydrobioids [7], three viviparids, and four pulmonates.  I feel certain that all have benefited from the endangered status of their most-famous member.

[7] Counted among the Limestone Creek hydrobioids is a population of Marstonia olivacea, which is a senior synonym of Marstonia ogmorhaphe, which was the other gastropod entered onto the Federal Endangered Species list 15Apr94.  And hence that hydrobiid population should be every bit as federally-protected as the pleurocerid "Athearnia anthonyi," but it isn't, because public policy has absolutely nothing to do with science.  For more, see:

• Is Marstonia olivacea extinct? [19Sept23]

Anchored hybrid enrichment, Leptoxis lessons, and the advice of Queen Elsa

Editor’s Note – This is the third installment of a three-part series reviewing the 2022 paper by Whelan and colleagues [1] on “Prodigious polyphyly in the Pleuroceridae.”  We recommend that you back up and read both our posts of September [23Sept25] and October [14Oct25] if that material isn’t fresh in your mind.  You will also find our posts of [6Apr23] and [9May23] helpful as background for the essay that follows, if you want to dig more deeply into the subject matter itself.

Back in early September I enjoyed a wonderful two-week field trip to the Ozark/Ouachita Highlands of Arkansas, southern Missouri, and eastern Oklahoma, logging 3,700 miles on my pickup and 20 miles on my kayak, collecting 59 sites.  And I am looking forward to sharing a lot of stories about my adventures in that biogeographically fascinating part of the world with you all in future posts.  Some of the observations I made on Leptoxis arkansensis during that memorable excursion are, however, especially relevant to the “prodigious polyphyly” discovered by Nathan Whelan and his colleagues [1] in the AHE phylogenomic study we are currently reviewing.

Populations of Leptoxis arkansensis are uncommon and widely scattered in the region, primarily inhabiting the rocky riffles of small rivers with good water quality, always (as far as I can tell) co-occurring with large and nearly-omnipresent populations of Pleurocera potosiensis.  From all evidence, the two are distinct biological species.  The shells borne by L. arkansensis demonstrate a larger body whorl than those of P. potosiensis, consistently and reliably, from birth to maturity.  But their grossly similar morphology in overall shell form can render the two species difficult to distinguish in the field.  There is not a shadow of doubt in my mind that they are “sister” species, one evolved from the other.

The strongest hypothesis, I would suggest, is that the original population of Leptoxis arkansensis evolved from a Pleurocera potosiensis population specialized for life in the riffles at midstream, and that the larger body whorl reflects a relatively larger foot, adapted for clinging to rocks in rapid currents.  Might that same adaptation have evolved more than once in the hundred-million-year history of the North American Pleuroceridae?  Who among my vast and erudite readership could imagine any answer to my rhetorical question other than the affirmative [2]?

The most loyal and patient among you might remember a (rather personal) essay I posted back in [6Apr23] entitled, “Growing Up With Periwinkles.”  In that post I reviewed my own 60+ years of experience with Leptoxis in the Southern Appalachians, from childhood through college and into my professional career, including several allozyme studies and even one (rather atypical, for me) sequence study as well.  I concluded that essay as follows: “If you had asked me ten years ago, I would have listed six valid species of Leptoxis in North America: carinata, praerosa, crassa, picta, plicata, and maybe that weirdo way out in the Ozarks, Leptoxis arkansensis (Hinkley 1915), I have no reason to doubt.”

Then, in the essay that followed [9May23], I “tested the periwinkle hypothesis” with the four-gene phylogeny (CO1, 16S, 28S, H3) that Nathan Whelan developed for his (2013) dissertation [3], finding solid agreement with my six-species model.  The main trunk of Nathan’s gene tree showed L. praerosa, L. crassa, L. carinata and L. picta distinct as expected.  Leptoxis plicata and L. arkansensis were also distinct, but depicted way off in the distant foliage with a variety of pleurocerids representing other genera.

There was also one surprise – evidence of a cryptic species sympatric with Leptoxis praerosa through much of their shared range in East Tennessee and North Alabama.  Nathan identified that cryptic species, quite problematically, as Leptoxis virgata. At the end of my [9May23] essay I had renamed my hypothesis for the genus Leptoxis in North America the 6* Species Model, adding that asterisk for the possibility of a seventh, cryptic species.

Figure 4 of Whelan et al [1]

Both of those 2023 essays were focused entirely on evolutionary relationships at the species level and below.  I wouldn’t say that I myself am entirely disinterested in evolution at higher levels, it just seems to me that we ought to work out some plausible hypotheses for the populations and the species first.  So now, with the 6* Species Model firmly supported both by Nathan’s 4-gene dissertation and by my own 60+ years of experience in field and laboratory, we are in a position to understand what Nathan’s more recent AHE phylogenomic analysis is telling us about the evolution of Leptoxis as a genus.  Then starting at three o’clock in Nathan's circular-format AHE tree above, and proceeding clockwise:

Leptoxis picta.  Way back in 1998, our good buddy Chuck Lydeard and I published a paper [4] showing that the allozyme divergence among six populations of three nominal species of Alabama Leptoxis: L. picta, L. ampla, and L. taeniata (subsequently [5] renamed coosaensis), was no greater than the divergence among control Leptoxis populations sampled from the Tennessee drainage, which nobody had ever suggested were anything other than L. praerosa.  We suggested that those three Mobile Basin nomina be united under the oldest name, Leptoxis picta (Conrad 1834).

Since 1998, an impressive body of research has been published supporting that hypothesis.  Nathan’s four-gene dissertation [3] returned negligible divergence among picta, ampla, taeniata/coosaensis, and foremani (7 populations, 18 individuals).  And both of Nathan’s (really quite lovely) subsequent studies of interpopulation divergence in “Leptoxis ampla,” his (2016) study of mitochondrial superheterogeneity [6] and his (2019) RADseq study [7], recovered strikingly high levels of interpopulation divergence, which easily extrapolate to include Mobile Basin populations historically identified as picta, taeniata/coosaensis, and foremani.

Now open before us we have a fifth study, estimating levels of genetic divergence among 192 individual pleurocerid snails over their entire single-copy genomes using the cutting-edge technique of Anchored Hybrid Enrichment, showing exactly the same result as references [3], [4], [6], and [7].  The nomina ampla, coosaensis, foremani and taeniata are all obsolete, junior synonyms of L. picta.  And to find the branches of a 21st century phylogenomic tree cavalierly decorated all about its entire periphery with 19th century superstition is an embarrassment to our entire profession.

Leptoxis carinata.  Quite independently of the evolution of Leptoxis picta in the Mobile Basin of Alabama, Nathan’s AHE phylogenomic analysis suggests a second origin of the genus Leptoxis in the southern Appalachians.  This origin is likely much older.

The sequencing studies I published with John Robinson in 2009 confirmed that Ohio drainage populations identified as Leptoxis dilatata (Conrad 1835) are conspecific with Atlantic drainage populations identified (since 1792!) as Leptoxis carinata, and suggested that the pleurocerid fauna of this ancient region might have evolved at the (Paleozoic) Appalachian orogeny [8].  Both the conspecific status of the two nomina, and the origin of Leptoxis carinata (now more broadly and properly understood) independent of any other Leptoxis species, were confirmed by Nathan’s dissertation [3], and have now been triple-checked by the AHE phylogenomic analysis under review here.

Leptoxis crassa and praerosa.  Again dovetailing nicely with his (2013) dissertation research, Nathan’s big AHE phylogenomic analysis confirms that Leptoxis crassa (identified here under the obsolete [9] synonym “Athearnia anthonyi”) is related to, but specifically distinct from, Leptoxis praerosa.  And the larger set of crassa + praerosa together apparently represents a third independent evolution of the shell morphology we associate today with the genus Leptoxis.  This third origin seems to have occurred in the Tennessee/Cumberland region, I should guess after Leptoxis carinata evolved further east, but before L. picta to the south.

Burrowing more deeply into that lovely lavender subcluster, we find further confirmation of Nathan’s 2013 results suggesting that umbilicata (Weatherby 1876) and subglobosa (Say 1825) are junior synonyms of L. praerosa (Say 1821).  Somewhat surprisingly, however, Nathan’s AHE analysis did not return evidence of any significant genetic distinction between two individuals he identified as L. virgata (only one of which is depicted below) and the larger L. praerosa cluster.

You might recall from my [9May23] review of Nathan’s dissertation that he did not specify any morphological trait by which his L. virgata could be distinguished from sympatric populations of L. praerosa, and that the genetic difference was apparently only mitochondrial, not nuclear.  Here ten years later, we are left wondering whether Nathan might have misidentified both of his nominal virgata specimens in 2022, or if the evidence he adduced in 2013 that a second biological species might be cryptic under our old friend Leptoxis praerosa might have been an atypically widespread case of mitochondrial superheterogeneity [11].

 

Leptoxis arkansensis.  We reviewed this branch of Nathan's AHE phylogenomic tree at the top of this essay.  The independent origin of Leptoxis arkansensis way out west in the Ozark highlands seems to be yet a fourth evolution of the shell morphology we associate today with the genus Leptoxis. 

 

Leptoxis plicata.  Even as the 1998 allozyme study of Dillon & Lydeard [4] was returning conspecific levels of genetic divergence among Alabama populations of Leptoxis picta, ampla, and taeniata/coosaensis, a fourth nominal species of Leptoxis from the state of Alabama, Leptoxis plicata, was revealed to be genetically distinct.  The single population of L. plicata known at that time, inhabiting the Locust Fork of the Black Warrior River, bore shells with a characteristically high apex and weak but distinctive plication on the upper whorls. 

 

From Whelan et al [1]

Additional evidence for the validity of L. plicata as a biological species was brought to light in 2013, with the publication of Nathan Whelan’s dissertation [3]. Nathan’s four-gene phylogeny depicted L. plicata as quite distantly removed from the other Alabama Leptoxis species, distant indeed from (almost) all other populations ever identified as Leptoxis anywhere, way off on a branch with clusters of Pleurocera and Lithasia.

Regarding that parenthetical modifier, “almost.”  I did not mention it at the time of my [9May23] review, but it is certainly worthy of note today, that in 2013 Nathan seems to have found very little sequence divergence between Leptoxis plicata and a newly-rediscovered Leptoxis population inhabiting the Cahaba River about 50 km south of Locust Fork, which he identified as Leptoxis compacta [13].  Here’s the copy of Nathan’s gigantic Baysian tree that I first made available for download from my 2023 review, with the little plicata/compacta cluster encircled in red:

[Whelan 2013 Figure 5.4, modified]

To objectively evaluate the significance of the evolutionary relationship between L. plicata and L. compacta, perhaps among the first data sets of interest would be their percent sequence divergence.  Alas, Nathan never uploaded any of the sequence data from his massive dissertation to GenBank.  But holding Nathan’s gigantic 2013 gene tree at arm’s length and scanning for an overall impression, L. plicata and L. compacta appear conspecific, the former nomen (Conrad 1834) having priority over the latter (Anthony 1854).

Now here ten years later, we find Leptoxis plicata and L. compacta again depicted as conspecific in Nathan’s AHE phylogenomic tree.  I myself have no biological insight to contribute, my experience with the legendary pleurocerid fauna of the Cahaba River being limited to song, story, and musty chronicle.  The descriptions I have read and the figures I have seen of the L. compacta shell do not mention shell plication, but do show the same unusually high spire characteristic of L. plicata.

In any case, I am sure we can all agree that the shell morphology borne by the Locust Fork / Cahaba pleurocerid populations together, clustered as both are upon the far-flung branches of every gene tree they’ve ever hung, suggests yet another separate origin of the genus Leptoxis.

 

So, to summarize the first 71% of the present essay.  Nathan’s AHE phylogenomic analysis confirms the 6-Species Model for the genus Leptoxis, without an asterisk.  The rocky shoals of North American rivers are inhabited by, in order of their description, Leptoxis carinata (Brug. 1792), L. praerosa (Say 1821), L. picta (Conrad 1834), L. plicata (Conrad 1834), L. crassa (Hald. 1841), and L. arkansensis (Hinkley 1915).  And the shell morphology that has historically served to unite these six biological species into the genus Leptoxis has evolved five separate times.

 

The first genus-level name to be proposed for the freshwater cerithiaceans of North America was, apparently [14], Pleurocera. And it was the eccentric French naturalist Constantine Rafinesque who did the proposing, way back in 1818.  The shell that he seems to have had in his hand at that time was elongate, with a high spire and small body whorl, best-guess-identified today as Pleurocera canaliculata [15].

 

And the second genus-level name proposed for the North American freshwater cerithiaceans was like unto the first, also proposed by Rafinesque, one year later.  That genus name was Leptoxis.  And the shell that Rafinesque seems to have had in his hand at that juncture was rotund and obovate, with a low spire and a large body whorl, best-guess-identified today as Leptoxis praerosa [15].

 

Thus, it seems that even prior to the birth of American malacology, when Frenchmen were still running around loose in our backwoods with butterfly nets, everybody who has ever pulled more than one pleurocerid snail out of our crystal-clear waters has divided out a subset bearing shells that are elongate and a subset bearing shells that are obovate.

Rafinesque (1783-1840)

Additional subsets were carved out as the nominal species accumulated, of course.  Generally following Goodrich, Burch [10], suggested a seven-genus system for the North American Pleuroceridae, most of those seven genera with subgenera, and listed an additional 25 genus names in synonymy.  But that elongate/obovate dichotomy has always been the most fundamental, and the Pleurocera/Leptoxis division the first.

So today we sit at our desks, a remarkably plausible reconstruction of the evolutionary history of the North American Pleuroceridae blossoming before us in lovely pastel shades of yellow, green, blue, and lavender.  And it seems quite appallingly evident that the very first taxonomic distinction made by our forefathers, around which 200 years of taxonomy subsequently developed, has no evolutionary basis.  Shall we then discard the entire richly historic but scientifically obsolete classification system of the Pleuroceridae?

 

No.  The binomial system of nomenclature was not first proposed by Carl Linnaeus in 1758 for any evolutionary purpose whatsoever.  It was first a tool for information storage and retrieval, and it served that function alone for its first 100 years of application, carrying Darwin toward the Theory of Evolution just as surely as The Beagle.  And that information-retrieval function continues to be the primary utility of biological taxonomy even to the present day.

 

I absolutely understand that the names of organisms must be changed to reflect scientific advance, and have certainly done my fair share of the changing.  But when we change a name, we pay the price of losing some of the information that the previous name historically transmitted.

 

The reason I synonymized Goniobasis and Elimia under Pleurocera in 2011 [16] was my discovery that single randomly-breeding populations of freshwater gastropods were being classified into three genera – not just in one case, but repeatedly, throughout the North American pleurocerid fauna.  The cost of the misinformation being generated by the Pleurocera/Goniobasis/Elimia confusion outweighed, in my judgment, the cost of the good information lost by the combination of those three names.

 

And I would invite Nathan Whelan and all our mutual colleagues, once again, to follow suit on that.  Look at that tangle of blue and yellow branches in the GHIJKL quadrant of your tree, colleagues!  Your own analysis shows that there is no evolutionary basis for the genus name “Elimia.” 

 

I understand your fervent desire to preserve obsolete nomina for the information they transmit.  I would point out, however, that “Goniobasis” contained even more information than “Elimia” when Burch [10] high-handedly dumped Goniobasis for an obscure point of taxonomic priority in 1980, yet our discipline survived.  And I would argue that the profits we all stand to gain by correcting the misinformation being promulgated even unto the present day by the entirely artificial distinction [17, 18] between Elimia and Pleurocera far outweigh the loss of good information we will suffer synonymizing the former under the latter.

 

But as to the other Burch/Goodrich genera – Lithasia, Io, Gyrotoma and especially Leptoxis, I believe that we have now reached consensus.  Can we all agree to take Queen Elsa’s advice, henceforth?  Let it go.

Notes:

 

[1] Whelan, N. V., Johnson, P. D., Garner, J. T., Garrison, N. L., & Strong, E. E. (2022). Prodigious polyphyly in Pleuroceridae (Gastropoda: Cerithioidea). Bulletin of the Society of Systematic Biologists, 1(2). https://doi.org/10.18061/bssb.v1i2.8419

 

[2] Here I have answered a rhetorical question with a second rhetorical question.  And this isn’t even rhetoric, it is prose.  Have I violated some ancient and hoary guideline?  If so, I plead ignorance, and apologize.

 

[3] Whelan, Nathan V. (2013) Conservation, life history and systematics of Leptoxis Rafinesque 1819 (Gastropoda: Cerithioidea: Pleuroceridae).  PhD Dissertation, University of Alabama, Tuscaloosa.  179 pp.  For a review, see:

• Testing the periwinkle hypothesis [9May23]

[4] Dillon, R.T., and C. Lydeard (1998) Divergence among Mobile Basin populations of the pleurocerid snail genus, Leptoxis, estimated by allozyme electrophoresis.  Malacologia. 39: 111-119. [pdf]

 

[5] Whelan, Nathan V.; Johnson, Paul D.; Garner, Jeffrey T.; Strong, Ellen E. (2017). On the identity of Leptoxis taeniata – a misapplied name for the threatened Painted Rocksnail (Cerithioidea, Pleuroceridae). ZooKeys (697): 21–36. https://zookeys.pensoft.net/article/14060/

 

[6] Whelan, N.V. & E. E. Strong (2016) Morphology, molecules and taxonomy: extreme incongruence in pleurocerids (Gastropoda, Cerithiodea, Pleuroceridae). Zoologica Scripta 45: 62 – 87.  For a review, see:

• Mitochondrial superheterogeneity and speciation [3May16]

[7] Whelan, N.V., M.P. Galaska, B.N. Sipley, J.M. Weber, P.D. Johnson, K.M. Halanych, and B.S. Helms (2019)  Riverscape genetic variation, migration patterns, and morphological variation of the threatened Round Rocksnail, Leptoxis ampla.  Molecular Ecology 28: 1593 – 1610.  For a review, see:

• Intrapopulation gene flow, the Leptoxis of the Cahaba, and the striking of matches [2Nov21]

[8] 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. [pdf] For a review, see:

• The snails the dinosaurs saw [16Mar09] 

[9] Jack Burch [10] lowered “Athearnia” to subgeneric status under Leptoxis way back in 1980, as he lowered “anthonyi” to subspecific status under crassa.  The relentlessly archaic taxonomy to which Nathan Whelan and his colleagues cling is not even current to the 20th century, much less the 21st.

 

[10] 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).

 

[11] The phenomenon of mitochondrial superheterogeneity was first documented in the pleurocerid snails by Dillon & Frankis [12] and made famous in 2009 by Dillon & Robinson [8].  The term was not actually coined until 2016, however, in a series of posts on this blog.  See:

• Mitochondrial superheterogeneity: What we know [15Mar16]
• Mitochondrial superheterogeneity: What it means [6Apr16]
• Mitochondrial superheterogeneity and speciation [3May16] 

[12] 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].

 

[13] Whelan NV, Johnson PD, Harris PM (2012) Rediscovery of Leptoxis compacta (Anthony, 1854) (Gastropoda: Cerithioidea: Pleuroceridae). PLoS ONE 7(8): e42499. https://doi.org/10.1371/journal.pone.0042499

 

[14] The actual meaning of Rafinesque’s 1818 nomen “Pleurocera” was shrouded in mystery and roiled by controversy for many years.  For a review, see:

• Joe Morrison and the great Pleurocera controversy [10Nov10] 

[15] Both Pleurocera canaliculata and Leptoxis praerosa were described by Thomas Say in 1821.  Yes, it is possible to describe a genus before its type species.

 

[16] Dillon, R. T. (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] 

[17] For a demonstration of the artificiality of the genus nomen Elimia, see:

• Goniobasis and Elimia [28Sept04] 

[18] And for a demonstration of the artificiality of the genus nomen Goniobasis, see:

• A House Divided [10May20]
  

Anchored Hybrid Enrichment and the prodigious clavaeformis confusion

Editor’s Note – This is the second installment of a projected three-part series reviewing the 2022 paper by Whelan and colleagues [1] on “Prodigious polyphyly in the Pleuroceridae.”  We recommend that you back up and read last month’s post [23Sept25] before proceeding onward, if that material isn’t fresh in your mind.  You will find a review of our August post [20Aug25] helpful, as well.  And in fact, refreshing your memory on our posts of September – November of 2016 [2] will also fill in a lot of the relevant background.  But that’s probably too much to ask.

Last month we summarized, to some modest level of detail, the fancy new technique called “Anchored Hybrid Enrichment” (AHE), recently wielded by a team of our colleagues headed up by Dr. Nathan V. Whelan of Auburn University to construct a phylogenomic tree of the North American Pleuroceridae.  AHE analysis begins with the development of “anchors,” DNA probes designed to target and enrich highly conserved regions within the genomes of the big set of organisms under study.  The slang term for these highly-conserved anchor regions is “bait.”

So, this month, let’s talk about bait.  Nathan and his team selected five probe species to “maximize phylogenetic diversity” across the Pleuroceridae, extracted mRNA from that small subset, and ultimately developed from the transcriptomes thereof 742 baits, requiring that they be present in at least four of the five probe species and larger than 120 bp in length.

Upon further review, I would not fuss about the identifications of three of those five probe species: Leptoxis “ampla” [3], “Elimia” crenatella [4], and Lithasia geniculata [5].  I could not find images of those three shells in the supplementary materials provided (USNM 1638590, 1638624, and 1638596, respectively) but I could find images of other nominally conspecific individuals bearing the same locality data, and they looked OK.

Pleurocera clavaeformis in Pistol Creek [6]

Let me set aside Nathan’s fourth probe species, “Pleurocera prasinata,” and come back to that situation later in this essay.  With regard to the fifth individual snail that the Whelan team selected for the generation of their AHE bait set, which they identified as "Elimia clavaeformis," what a mess.

Back in August [20Aug25] we reviewed the paper I published in 2011 [6] vividly demonstrating cryptic phenotypic plasticity in populations of that species, best identified today as Pleurocera clavaeformis, as they range across East Tennessee.  The shell morphology demonstrated by many upstream populations, historically identified as “Goniobasis (or Elimia) acutocarinata” is gracile with a striking peripheral carination.  The shell morphology of populations inhabiting mid-sized rivers and streams is what everybody has always associated with typical Goniobasis (or “Elimia”) clavaeformis.  And the shell morphology of big river populations, historically identified as “Pleurocera unciale,” is smoothly-rounded and robust.

Now look at Nathan Whelan’s Figure 5, as reproduced below.  Even given a healthy appreciation of the dramatic phenotypic variation in shell morphology that can be demonstrated by the pleurocerid populations of North America, do the four shells depicted across the top row of that figure look like the same species as the four shells depicted on the bottom row?  Who among my vast and far-flung readership cannot immediately distinguish two subsets of shells in Nathan’s figure: an ABCD group and an EFGH group?  Contact me immediately!  Your FWGNA credentials are in dire jeopardy.

The four shells in the EFGH group on the bottom row of Nathan’s figure below all belonged to individual Pleurocera clavaeformis acutocarinata, fine, as we just spent the entirety of our August post laboring over, no problem there.  But the pair of smooth, squat-looking shells in the upper right, labeled C and D, belonged to two Pleurocera simplex of very typical morphology.  And the pair of smooth, slender-looking shells in the upper left, labeled A and B, belonged to its sibling species, Pleurocera gabbiana.

“Figure 5. Shell morphology of Elimia clavaeformis s.l.” [1]

My readership can be forgiven for confusing simplex and gabbiana.  They co-occur in mixed populations throughout much of East Tennessee, and I myself was only able to distinguish them after rather tedious allozyme and morphometric studies, which I published in the FMCS newsletter Ellipsaria in 2016 [7], and relayed in three posts to this blog later that same year [2].

But alas, I bear bad news. A team of five professional malacologists, headed by our own colleague Nathan Whelan, identified all eight of the shells shown in Figure 5 above as belonging to “Elimia clavaeformis s.l.”

It is difficult for me to understand how the Whelan team missed my 2016 simplex/gabbiana series in Ellipsaria [8], near impossible for me to understand how they missed my 2011 paper on clavaeformis published in Malacologia, and inconceivable to me that they could confuse clavaeformis with simplex.  Yet that is exactly what they did.

Both shell A and shell F [9] were collected sympatrically at Turkey Creek, about 20 km W of Knoxville.  Both C and G were also collected sympatrically from Pistol Creek at Maryville, 25 km S of Knoxville, one of the four streams I myself sampled for my 2011 clavaeformis study, and also where I conducted my simplex/gabbiana study in 2016.  The reproductive isolation between the clavaeformis and simplex populations inhabiting those creeks is writ vivid on the shells of the animals that bear them, entirely distinctive, 100% sortable at streambank.  For five of our colleagues to confuse P. clavaeformis with P. simplex/gabbiana four separate times, cavalierly dismissive or abysmally ignorant of previously published research, and advertise their abject confusion in a full-page montage in an international scientific journal, is the most inconceivable concatenation of error upon error since Vizzini drank the goblet.

Now here is some good news.  Nathan’s supplementary material included a photo of the shell on the back of the individual snail from which he developed his AHE bait set, and it turns out to have indeed belonged to a Pleurocera clavaeformis acutocarinata.  So, his initial identification was correct.

And here is a second item of even better news.  Even if that snail had been misidentified, it would not have mattered.  To generate a good AHE bait set, all that really mattered to the Whelan team was that the five probe species they selected cover the range of genetic divergence across the 194 snails they intended to troll with them.  Which four of the five probe species certainly did.  Which almost brings us back to probe species #4 (of 5), which Nathan identified as “Pleurocera prasinata.”  But let’s put that issue off again.  And continue to move forward.

Seven of the eight snails depicted in Figure 5 above were included among the 194 test individuals in Nathan’s overall AHE analysis, and those seven did appear hanging among the branches in the big set of huge phylogenomic trees (generated under various assumptions) that he made available in his supplementary material.  Nathan only selected a couple of the Figure 5 shells to depict on the pretty tree he ultimately published as Figure 4 in the journal article, reproduced below.  But the bottom line is this.

Figure 4 of Whelan and colleagues [1]

Snails A and B clustered in the group I have labeled Pleurocera gabbiana and snails C and D clustered in the group I have labeled Pleurocera simplex.  Snail G (Pistol Creek) clustered in another big group a bit further around clockwise, with taxa Nathan labeled prasinata, acuta, pyrenella, attenuata, and so forth.  And snails E (Town Creek, not depicted) and F (Turkey Creek, depicted) clustered in a group much further around on the other side of the tree, between a snail Nathan labeled arachnoidea and a snail he labeled edgariana.

Knowing what we know about the biology of these remarkable organisms, the placement of the Pistol Creek individual is correct.  Look back up at the top of this essay, to that detail from Figure 2 of my 2011 paper.  As I mentioned above, the Pistol Creek P. clavaeformis population was one of the four I selected for allozyme analysis in that research.  My sample CA2 was taken from the exact spot that Nathan collected his individual Pistol Creek snail, an upstream reach running through a lovely little park in downtown Maryville.  I also sampled the Pistol Creek P. clavaeformis population 8 km further downstream, where it demonstrated the typical shell morphology depicted as C2.  And the shell labeled P2 was collected another 6 km downstream and out into the Little River.  That robust P2 shell phenotype, historically identified as “Pleurocera unciale” throughout East Tennessee, is indistinguishable from the shells Nathan has identified as “prasinata” and “aff. acuta” in his Figure 4 above.

And now at last, we see the problem with Nathan’s selection of both “Elimia clavaeformis” and “Pleurocera prasinata” as probe species from which to develop his AHE baits.  Far from “maximizing phylogenetic diversity,” those two nominal species appear so genetically similar as to be conspecific [10].

So now let’s turn our attention to that pair of P. clavaeformis acutocarinata (only one of which was figured) collected from Turkey Creek and Town Creek clustered way off in the upper left quadrant of Nathan’s tree with arachnoidea and edgariana.  Science is the construction of testable hypotheses about the natural world.  Let’s do some science.

In a series of essays posted on this blog late last year I reviewed what we know about interspecific hybridization in the North American Pleuroceridae, documented widespread hybridization between Pleurocera laqueata and P. troostiana in Middle Tennessee, North Alabama, and Kentucky, and suggested that reticulate evolution may have played a significant role in the diversification of the family across eastern North America generally [11].

The nomen “Elimia arachnoidea” depicted immediately above the Town/Turkey acutocarinata in Nathan’s Figure 4 is a junior synonym of Pleurocera troostiana, and the nomen “Elimia edgariana” depicted immediately below is a troostiana/laqueata hybrid [12].  The “Elimia sp. Red River” below edgariana is unidentifiable, but next below Red River is “Elimia curreyana,” a junior synonym of Pleurocera laqueata.  My hypothesis is that both of the individual snails sampled from Town Creek and Turkey Creek are clavaeformis/troostiana hybrids, a possibility I mentioned at the end of my essay back in August [20Aug25].

Or, the misplacement of the Turkey and Town Creek individuals might be attributable to a couple mislabeled sample tubes.  Or a spreadsheet error.  Any one of a million things could have gone wrong, who knows?  The larger point I am making here is that, because we bring an understanding of the evolutionary relationships of these animals to Nathan’s elaborate phylogenetic analysis, we can recognize error when it occurs.  Those two snails should have clustered with the conspecific Pistol Creek individual below.

In any case, regardless.  One might pray that, at the conclusion of his complex and intricate study, with his voluminous set of AHE results unfolded across the desk in front of him, showing the eight snails he had initially identified as “Elimia clavaeformis” splattered into four clusters across three quadrants of his colorful and richly-detailed Figure 4, Nathan Whelan might have been able to diagnose his prodigious clavaeformis confusion.  Alas, no. Ultimately, Nathan identified the incongruous collection of pleurocerids depicted in his Figure 5 as “two distinct lineages of E. clavaeformis and of its putative synonym, E. acutocarinata.”  Of such is prodigious polyphyly born.

I have said it, by actual count, 73 times over the 28-year history of this blog, but I am going to say it again, number 74, count ‘em all.  Gene trees are dependent variables, not independent variables.  They can be useful to test an hypothesis brought to them; they cannot yield an hypothesis to test.  They are the last chapter of your dissertation, not the first. Only if you have developed an understanding of the evolutionary relationships of a set of organisms by finer, independent means, can you interpret what a gene tree is telling you.

But let us finish this month’s essay on the same positive note with which we ended in September.  Bringing a finer understanding of the evolutionary relationships among the North American pleurocerid snails with us to the analysis, Nathan Whelan’s AHE gene tree really does have something important to tell us about the entire pleurocerid forest.  Which we will interpret together, next time.

Notes:

[1] Whelan, N. V., Johnson, P. D., Garner, J. T., Garrison, N. L., & Strong, E. E. (2022). Prodigious polyphyly in Pleuroceridae (Gastropoda: Cerithioidea). Bulletin of the Society of Systematic Biologists, 1(2). https://doi.org/10.18061/bssb.v1i2.8419

[2] My blog posts on the Pleurocera simplex/gabbiana sibling species pair:

• 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]

[3] Well, I suppose I might fuss a bit about identifying any population of pleurocerids as Leptoxis “ampla.”  At least three good studies have been published in recent years strongly suggesting that Anthony’s (1855) nomen ampla is a junior synonym of Conrad’s (1834) picta.  More next month.

[4] I don’t have any insight to offer regarding the evolutionary relationships between pleurocerid populations identified as “Elimia crenatella” in Alabama and any of the other scores of nominal pleurocerid species inhabiting the malacologically benighted Mobile Basin.  This is because I have very little field experience in the region to draw upon.  Still waiting on my invitation, long time coming.

 

[5] For more about the fascinating evolutionary biology of Lithasia geniculata, see:

• Intrapopulation gene flow: Lithasia geniculata in the Duck River [7Dec21]
• What is character phase disequilibrium? [4Jan22]
• The third-most amazing research results ever published for the genetics of a freshwater gastropod population, and the fourth-most amazing, too. [3Mar22]

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

 

[7] My series of published notes on the simplex/gabbiana sibling species pair:

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

[8] Some not-insubstantial irony here.  From 2016 - 2020 I regularly published my technical results as notes in the FMCS Newsletter, “Ellipsaria.”  That stopped in 2020, when it was called to the attention of editor John Jenkinson that Ellipsaria contents were being indexed by Google Scholar, and hence that results such as mine might be reaching a wider audience.  According to the minutes of the FMCS Board Meeting of November 2, 2020, the complaint that prompted Dr. Jenkinson’s decision was lodged by one Dr. Nathan V. Whelan.

[9] I caught a small error in the caption of Nathan’s Figure 5.  Shells A and F were collected from Turkey Creek, not A and E.

 

[10] I both elaborated and belabored the genetic similarity between East Tennessee populations of Pleurocera clavaeformis and Alabama populations identified as “Pleurocera prasinata” back in 2016, here:

• Pleurocera clavaeformis in the Mobile Basin? [12July16]

[11] For a review of intraspecific hybridization in the North American Pleuroceridae, see:

• Widespread hybridization between Pleurocera laqueata and P. troostiana in streams of the Tennessee/Cumberland [15Oct24]
• Reticulate evolution in the North American Pleuroceridae [12Nov24]

[12] And for a review of the taxonomic consequences of widespread hybridization in pleurocerid populations referred to arachnoidea, edgariana, curreyana, and 23 other specific nomina, see:

• Taxonomy of the Pleurocera laqueata/troostiana complex. Part I [10Dec24]
• Taxonomy of the Pleurocera laqueata/troostiana complex, Part II [14Jan25]