Megapetitions of the Old West

There's a new posse riding the plains, and they're aiming to make the American West safe for all its law-abiding citizens, including the malacological ones. And on their hips, they're toting sawed-off scatterguns.

The Center for Biological Diversity (CBD) is celebrating its twentieth anniversary this year. There's a beautifully-formatted booklet available for download from their web site packed full of dramatic tales such as "A bare-knuckled trio takes on Big Timber" and "Sprawl Showdown." With a main office in Tucson, and field offices in eight other states, their staff of 60 (including 17 lawyers) works "to secure a future for all species, great and small," with a "vision and a solar-powered fax machine.

"Their efforts thus far have been impressive. In recent years CBD gunslingers have prevailed in shootouts over Pyrgulopsis roswellensis, Juternia kosteri and Assiminea pecos in New Mexico, as well as P. morrisoni in Arizona. Their web site (accessed 10July09) catalogues 86 listing petitions, 5 critical habitat petitions, and 9 species status reviews along with scores of "research papers."

Recently the CBD posse seems to be dramatically expanding its efforts on behalf of our favorite creatures with a couple petitions along an unusual line of approach. Taking advantage of the 1994 FWS policy encouraging "Multi-species listings…when several species have common threats, habitat, distribution, landowners, or features that would group the species and provide more efficient listing and subsequent recovery,” in 2008 the CBD filed "Petition to list 32 mollusk species from freshwater and terrestrial ecosystems of the northwestern United States as Threatened or Endangered under the Endangered Species Act." [PDF, 2.0 MB] Then in February of this year they let loose with an even bigger blast, "Petition to list 42 species of Great Basin Springsnails from Nevada, Utah, and California as Threatened or Endangered under the Endangered Species Act." [PDF, 1.7 MB]

The 2008 volley, weighing in at 85 pages, proposed 17 freshwater snails of three familes for protection: 14 hydrobiids (11 Fluminicola, 3 "Lyogyrus"), 2 pleurocerids (Juga), and one planorbid (a Vorticifex), as well as 15 land snails of diverse groups. The taxonomy was a complete mess, and the document an embarrassment (1). The causes of three valid species (Fluminicola seminalis, F. potemicus, and Colligyrus convexus) were buried under the weight of 14 spurious taxa proposed in various unpublished reports by the late Terry Frest. I hope that the poor FWS biologist sitting behind the desk on which this dead coon is currently stinking can find it in his heart to forgive us.

So the 2009 petition, tipping the scales at 133 pages, could only be better. The 42 hydrobiid species it proposes for protection include 37 Pyrgulopsis and 5 Tryonia, all endemic to single springs or sets of springs in Nevada or closely adjoining regions (For example, the spring at Point of Rocks figured above, in the Ash Meadows National Wildlife Refuge, NV). All 42 species have been recently monographed by (in fact, mostly described by) Bob Hershler (2). I don't have any personal experience in this part of the world, but from my seat on the corral fence, if these diminutive citizens of the Old West don't need a bit of protection, I don't know who does.

The advantage of a megapetition approach ought to be in speed and efficiency. The 2009 petition features just one (collected) section entitled "Natural History and Ecology" for the entire list of 42 species, and I think this is justifiable. Treating all these populations together where possible ought to yield substantial savings in time and manpower for the CBD to research, and the FWS to process - savings which should translate into quicker results.

But on the downside, weakness in any element of a megapetition may translate to the whole. It's hard to sell a bag of 17 apples and 15 oranges, when 14 of the apples are rotten.

Both the 2008 and 2009 petitions called the attention of the Secretary of the Interior to laws "placing definite response requirements on the FWS and very specific time constraints on those responses." Apparently federal regulations require that the FWS respond to petitions such as these in 90 days. Well, I don't think anybody actually expected that to happen. The FWS simply does not have the staff or the expertise to evaluate documents of this heft at time scales marked in days. I understand that it generally requires a minimum of 15 months to obtain a 90-day finding, 15 months being the earliest point at which a "timeline suit" can be filed.

So it looks like our little snails will be holding off the development desperados by themselves a little bit longer. In the meantime, we'll keep an ear to the rail, and an eye toward the sunset.

Notes

(1) I am not criticizing the CBD here. Their proposal can only be as strong as the science on which it is based.

(2) Hershler, R. & D.W. Sada (1987) Springsnails (Gastropoda: Hydrobiidae) of Ash Meadows, Amargosa Basin, California-Nevada. Proc. Biol. Soc. Wash. 100: 776-873. Hershler, R. (1994) A review of the North American freshwater snail genus Pyrgulopsis (Hydrobiidae). Smithsonian Contrib. Zoology 554: 115 p. Hershler, R. (1998) A systematic review of the hydrobiid snails (Gastropoda: Rissooidea) of the Great Basin, Western United States. Part I. Genus Pyrgulopsis. Veliger 41: 1-132.

Just One Species of Ferrissia

Editor's Note:  A substantial fraction of the material in this essay was subsequently rendered obsolete by the 2010 research of Walther and colleagues.  See my post of [8Dec10] for more.

I'm pleased to report the publication of a paper by J. J. Herman and myself in this month's Journal of Freshwater Ecology, "Genetics, shell morphology, and life history of the freshwater pulmonate limpets Ferrissia rivularis and Ferrissia fragilis (1)." In this work we offer evidence that populations of the two most widespread limpets in North America reproduce entirely by self fertilization, and that the shell morphological criteria by which they have been distinguished are the result of ecophenotypic plasticity. We suggest that the nomen Ferrissia fragilis is a junior synonym of F. rivularis.


The modern taxonomic history of the North American Ancylidae has been one of consolidation (2). Basch (3) recognized five species of Ferrissia (rivularis, fragilis, parallela, walkeri and mcneilli), noting as he did that "ecological phenotypes are numerous, and plasticity of shell form has been remarked upon many times." (See Basch's charming figure above). More recently Andrea Walther's sequence data have suggested just two Ferrissia lineages, which she has correlated with the rivularis and fragilis phenotypes and life habits (4).

But our discovery of asexual reproduction voids the biological species concept, and necessitates a retreat to the morphological. And since there seems to be no heritable component to the shell characters conventionally used to distinguish rivularis and fragilis (see figure below), it would appear that a single-species model fits the situation best.

I gather that Andrea and her advisor Dairmaid O'Foighil prefer to retain the two species model, under one of the many species concepts based on gene trees. But the limitations of the various phylogenetic and cladistic species concepts are well known (5).

The situation with Ferrissia in North America seems biologically analogous to that of the better-studied Ancylus fluviatilis in Europe. A phenotypically plastic response of shell height and shell thickness to current and substrate has been well known in A. fluviatilis populations for years, and Städler and colleagues (6) documented asexual reproduction in the mid-1990s. More recently Pfenninger and colleagues (7) have reported that 103 populations of A. fluviatilis sampled from across Europe can be grouped into four DNA clades. Yet European workers seem content to identify all their limpet populations by the same nomen, Ancylus fluviatilis.

If there were a reliable correlation between Andrea's gene trees and any criterion by which rivularis and fragilis have been distinguished in the past, an argument could be made for retaining both nomina as labels for asexual lineages. But Andrea misclassified the samples we sent her in 2007 from our North Saluda River population as F. fragilis, even though they were collected from a rocky stream and bore robust, acutely conical shells. One species of Ferrissia it would seem to be.

Notes

(1) Dillon, R. T., Jr. & J. J. Herman (2009) J. Freshw. Ecol. 24: 261-272. [PDF]

(2) See the FWGNA archives of July '07, "Phylogenetic sporting" in the genus Laevapex.

(3) Basch, P.F., 1963. A review of the recent freshwater limpet snails of North America (Mollusca: Pulmonata). Bull. Mus. Comp. Zool. Harvard Univ. 129: 399–461.

(4) Although I have seen some data from Andrea's recent Ph.D. dissertation at the University of Michigan, I have not seen the work itself. This is from my personal communication with Andrea and her advisor, together with the abstracts of talks she has given in recent years.

(5) See the FWGNA archives of July '08: Gene trees and species trees.

(6) Städler, T., M. Loew and B. Streit. 1993. Genetic evidence for low outcrossing rates in polyploid freshwater snails (Ancylus fluviatilis). Proc. R. Soc. Lond. B 251: 207-213. Städler, T., S. Weisner and B. Streit. 1995. Outcrossing rates and correlated matings in a predominantly selfing freshwater snail. Proc. R. Soc. Lond. B 262: 119-125.

(7) Pfenninger, M., S. Staubach, C. Albrecht, B. Streit and K. Schwenk. 2003. Ecological and morphological differentiation among cryptic evolutionary lineages of freshwater limpets of the nominal form-group Ancylus fluviatilis (O. F. Muller, 1774). Molecular Ecology 12: 2731-2745.

Freshwater Gastropod Databases Go Global!

Last month we reviewed the not-insubstantial progress that many of our larger national and regional research museums have made with electronic data capture, evaluating their on-line holdings of North American freshwater snails. Among the many nice comments I received from that post were several calling my attention to the Global Biodiversity Information Facility, a remarkable data network hosted in Copenhagen. Some of our colleagues feel strongly that the GBIF “Portal” represents the future of online museum databases worldwide.

The system is administered by a governing board, 30 participating countries, and 20 associate countries. It hosts (as of 26May09) over 174 million records across the diversity of eukaryotic life, contributed by 289 data providers worldwide. My query for “Campeloma” entered into the single, simple search box returned an impressive 3,210 records, as follows:

1,414 Florida Museum of Natural History
852 Academy of Natural Sciences, Philadelphia
498 North Carolina State Museum
145 University of Colorado Museum
127 US National Museum
55 Yale (Peabody) Museum
116 (Nine other institutions)

The FLMNH, ANSP, and USNM numbers are reassuringly close to the figures I obtained from my queries to their local on-line datbases, as reported last month. I didn’t think to look at the NCSM last month (Shame on me!) but the (rather impressive) 498 records I retrieved from the GBIF also closely approximate the results I would have gotten from a query to their local site, had I visited. I also didn’t think to look at the Peabody Museum last month, but in this case, the 55 records available from the GBIF are significantly improved over the 15 I would have come away with from a visit to their local on-line database. And the University of Colorado Museum records are a bonus – the UCM no longer maintains a local site, so it’s Copenhagen or nothing. The power of the GBIF idea is undeniable.

The GBIF portal features a gee-whiz mapping function for your results, which plots the occurrence of your taxon of interest on one-degree cells, with the capability of zooming to 0.1 degree and exploring. It also offers the option of exporting search results in several vanilla types of file formats, which you can download, sort and subsample to your heart's content.

So I've added a link to the Global Biodiversity Information Facility from the FWGNA information resources page, and I expect to be hitting that link with increased frequency in the coming years.

Progress in the Museums

To the FWGNA group:

It's been several years since we last took an electronic tour around the major systematic collections of North American freshwater mollusks. And it's nice to see such good progress being made in on-line database access. When the FWGNA project kicked off in 1998, only two national or regional collections of freshwater gastropods were effectively searchable on line: The Florida Museum and the ANSP. Today that small club has been joined by eight other museums. I'm impressed!

Databasing efforts are, of course, an ongoing project in all active systematic collections. But I thought it might be useful for our group if I took a snapshot of the distributional information available on-line for North American freshwater gastropods, as of April 2009. Developing an independent metric by which to evaluate and compare ten disparate databases was, however, something of a challenge.

My first thought was to query each database for all records of a common and widespread freshwater gastropod family, such as the Physidae. But alas, many of the ten databases are not searchable by family - only by genus or species. And most of the lower taxa are regional in their distributions and taxonomically unstable - not the best targets for a comparative search.

After some head-scratching, I've decided to evaluate the ten on-line databases by the number of Campeloma records currently retrievable. Campeloma is the most widespread and stable genus of North American freshwater gastropods I can think of, although its distribution does introduce a bias against museums with predominantly western holdings. The California Academy of Sciences ranks #8 by Campeloma, but would certainly rank above the Field Museum (#6) by physid records, if all the collections were rankable using that criterion. But for what it's worth:

(1) University of Michigan Museum of Zoology
Campeloma = 2,456
Searchable by Family = No

(2) Florida Museum of Natural History
Campeloma = 1,414
Searchable by Family = Yes (Physidae = 2,063)

(3) Academy of Natural Sciences, Philadelphia
Campeloma = 890
Searchable by Family = Not effectively

(4) Museum of Comparative Zoology, Harvard
Campeloma = 488
Searchable by Family = Yes (Physidae = 1,033)

(5) National Museum of Natural History, Smithsonian
Campeloma = 127
Searchable by Family = Yes (Physidae = 793)

(6) Field Museum of Natural History
Campeloma = 88
Searchable by Family = Yes (Physidae = 149)

(7) Illinois Natural History Survey
Campeloma = 62
Searchable by Family = No

(8) California Academy of Sciences
Campeloma = 2
Searchable by Family = Yes (Physidae = 290)

(9) Los Angeles County Museum
Campeloma = 1
Searchable by Family = Yes (Physidae = 3)

(10) Bailey-Matthews Shell Museum
Campeloma = 1
Searchable by Family = Yes (Physidae = 0)

All of these on-line databases, I'm pleased to report, are searchable by double criteria, such as species AND state/province. Two databases were able to handle my (rather complicated) "Physa OR Physella" query, by which I was trying to eliminate the double-counting of records where Physella is a subgenus but not a genus: MCZ and LACM.

Kudos to all our hard-working colleagues in the ten museums listed above! And for our colleagues working at the museums listed below - a word of encouragement. I know funding is tight, but we're all in this together. So hang in there, get those grants, we're rooting for you!

Other Museums visited, Collections not on line at present:
American Museum of Natural History
Canadian Museum of Nature
Carnegie Museum (Pittsburgh)
Delaware Museum of Natural History
Ohio State Museum

And keep in touch, everybody!
Rob

The Snails The Dinosaurs Saw

Editor’s Note – This essay was subsequently published as: Dillon, R.T., Jr. (2019c) The Snails The Dinosaurs Saw.  Pp 137 - 143 in The Freshwater Gastropods of North America Volume 3, Essays on the Prosobranchs.  FWGNA Press, Charleston.

I imagine most of us are familiar, at least in passing, with the North American Benthological Society ("NABS"), and their excellent journal, J-NABS (1). Published quarterly since 1982, J-NABS has built a solid reputation as an outlet for peer-reviewed research on any aspect of the biota "on the surface of the bottom" of lakes and rivers worldwide. The journal has rarely, however, been seen as a vehicle for anything edgy.

Perhaps in response to that perception, in 1998 a wealthy benefactor endowed the Rosemary Mackay Fund to support the publication of "speculative, forward-thinking, and philosophical" research in J-NABS. There have been four Rosemary Mackie Awards in the last ten years (2).

I am here pleased to announce that a paper by John Robinson and myself has been selected as the fifth winner of this prestigious award. Our work, entitled "The snails the dinosaurs saw: Are the pleurocerid populations of the Older Appalachians a relict of the Paleozoic Era?" leads off this month's issue of J-NABS. A download of the full article is available here [PDF].

One of the perks that accompanies a Rosemary Mackie Award is that the winning paper (and its authors) are featured in the NABS newsletter, In the Drift. This "Article Spotlight" feature for "The Snails The Dinosaurs Saw" is reprinted below (3). I apologize if the tone seems a bit self-indulgent - this seems to be what the editor was asking for.

This is, in any case, as edgy as freshwater snail research gets.
Read on if you dare!

Rob


JNABS Article Spotlight: Snails the Dinosaurs Saw

My grandmother once observed, “Robbie Tom sure do love to play in the crick.” This remark she made to my father, as they sat rocking on her front porch at the foot of the Blue Ridge in Patrick County, Virginia. I would have been about 25 years old at the time, sampling Goniobasis proxima from the stream in her back yard for my dissertation research (above).

In one sense, the research project yielding the results that John Robinson and I reported in our "dinosaur" paper would never have been initiated without the Rosemary Mackay Fund. Our hypothesis that a large group of obscure freshwater snails evolved on the west side of the towering ancient Appalachians hundreds of millions of years ago, and then rode the mountains down as they eroded almost to base level, without moving or even noticeably evolving, is simply too wild to publish as conventional science. But in a second, broader sense, I've been working on this project for 40 years.

Because my grandmother was right. For as long as I can remember, I have been playing in the rivers and streams of the southern Appalachians, where the most conspicuous element of the macrobenthos is the pleurocerid snails. Through my childhood in the Shenandoah Valley it was Leptoxis carinata, in the upper New River where I did my undergraduate research it was Goniobasis proxima, and through the piedmont of the Carolinas it was Goniobasis catenaria.

Common sense suggests that these populations must be ancient. The snails have such limited dispersal capabilities that significant gene frequency differences can develop across a three-meter corrugated metal culvert. Yet Goniobasis proxima populations are common in almost every little creek draining both sides of the Appalachian divide from southern Virginia to north Georgia. How could bird dispersal account for such a range?

So perhaps my colleague, Bob Frankis, and I should not have been surprised by the first DNA sequence data we obtained for three populations of G. proxima in the summer of 2000. We found tremendous genetic diversity both between and within populations – up to 16.9% sequence divergence between two G. proxima individuals collected from the same rock in a Dan River tributary from the Virginia Piedmont. To us, these results suggested both that our pleurocerid populations must be ancient, and that natural selection might have acted to distribute gene frequencies across a pair of quite distant adaptive peaks.

But to journal reviewers, such results could only mean one thing – cryptic speciation. My 20 years of data demonstrating random mating within local populations of G. proxima, and no evidence of reproductive isolation between them, carried no weight with most of my immediate colleagues. In the community of phylogenetic systematics, the biological species concept has been replaced by a variety of typological concepts that discount reproductive relationships. The little paper that Bob and I wrote was rejected by four journals, before I finally managed to get the thing published in an issue of the American Malacological Bulletin that I myself guest-edited in 2004. I vowed never again.

.

But in 2006 I read Pam Silver’s editorial in J-NABS, renewing the call for “speculative, forward-looking, and philosophical” articles to publish through the Rosemary Mackie Fund. And I was also fortunate to have John Robinson in my lab at the time (left). John came to Charleston as an M.S. student in Marine Biology, but was always eager for good research conducted in any environment, and blessed with molecular skills far superior to my own. So together we developed a sampling design to extend the results of Dillon & Frankis across 13 populations of three pleurocerid species, and over the eastern continental divide.

Such a project could never win external funding. The mainline systematic community is heavily invested in "Assembling the Tree of Life” using techniques dependent on an assumption of neutrality. Our hypothesis of multiple adaptive peaks in ancient and polymorphic populations is genuinely subversive to such a project. If true, it would imply that “The Tree of Life” can no better be reconstructed with molecules in the 21st century than it was with morphology in the 19th.

So oddly enough, the project overcame its final hurdle when John graduated and moved up to the University of Georgia. His Ph.D. adviser, John Wares, was both supportive and indulgent when a few samples of our freshwater snails slipped into the queue for his sequencer. Our special thanks go to Dr. Wares, as well as to the RMF Committee, for making this research possible.

The hypothesis we are advocating yields quite a few surprising predictions. In addition to challenging the basic assumptions of molecular phylogenetics, our model will upset most geomorphologists, who today think it unlikely that the eastern continental divide has migrated, and most malacologists, who postulate independent origins for American and African cerithiacean snails, and cryptic species in every creek.

But setting aside the craziness, John and I hope that our paper brings forward some assumptions that all we benthologists probably carry in the back of our minds, but may not examine as often as we should. Many elements of the freshwater biota are much older than those of the terrestrial environments surrounding them. All those ancient orders of aquatic insects, for example, probably evolved long before the seed plants that provide most of the primary productivity for the rivers they inhabit today. Standing at creek side, looking down, we look back millions of years. Even if our snails didn't see dinosaurs, that's an important thing to keep in mind.

Notes

(1) There's still time to register for the NABS annual meeting, scheduled for May 17 - 22 in Grand Rapids! Once again I've volunteered to man the Gastropoda booth at the "Taxonomy Fair" on the afternoon of the 19th. Come by to see me!

(2) The third in the series was by our colleague Dave Strayer (2006), Challenges for freshwater invertebrate conservation. JNABS 25: 271-287.

(3) The actual article, as it appeared on Page 2 of the Winter 2009 In The Drift, was shortened a bit for publication, and had several additional photos. [PDF]

Charles Darwin, Freshwater Malacologist

Editor's Note - Shortly after I posted this email, our good friend Aydin Orstan contacted me with a suggestion that we might add Darwin's research with land snails and collaborate on a larger paper.  This was ultimately published as Orstan & Dillon (2009) Charles Darwin the Malacologist. Mollusc World 20: 4 - 6 [PDF].

Charles Darwin, whose 200th birthday the world has just celebrated, may have been the last complete biologist. His research interests spanned the entirety of the life sciences as they were known in his day, from his "Monograph on the Subclass Cirripedia" (1851) through his "Descent of Man" (1871) to "The Power of Movement in Plants" (1880). Darwin’s first publication (1839) was a ripping-good adventure story featuring "atmo-spheric dust with infusoria (1)." And his last publication, a four-paragraph communication appearing in 1882 just two weeks before his death, was a work of freshwater malacology (2).

In fact, Darwin first touched on freshwater mollusks in his (1859) "Origin of Species." Early in the chapter he entitled "Geographical Distribution – Continued," Darwin observed, "Some species of fresh-water shells have very wide ranges, and allied species which, on our theory, are descended from a common parent, and must have proceeded from a single source, prevail throughout the world. Their distribution at first perplexed me much." But Darwin then went on to relay a number of anecdotes regarding the attachment of juvenile freshwater mollusks to the feet and feathers of waterfowl, concluding his lengthy paragraph with "Sir Charles Lyell informs me that a Dytiscus (3) has been caught with an Ancylus firmly adhering to it."

Darwin’s fascination with dispersal and biogeography brought him back to the subject of freshwater malacology again in 1878 (4), with a charming anecdote about a surprisingly large unionid mussel found attached to the toe of a duck shot in Danversport, Massachusetts (figure at left). And it reached full flower in 1882, with his "On the Dispersal of Freshwater Bivalves (5)."

Darwin opened this, the last paper he would publish before his death, with "The wide distribution of the same species, and of closely-allied species of freshwater shells must have surprised every one who has attended to this subject." After reviewing his observations of 1859 and 1878, Darwin wrote, "I am now able to add, through the kindness of Mr. W. D. Crick, of Northampton, another and different case. On February 18 of the present year, he caught a female Dytiscus marginalis, with a shell of Cyclas cornea (6) clinging to the tarsus of its middle leg." Darwin went on to relay additional data about this now most illustrious of all fingernail clams, which was large (0.45 inch), viable (dropping from the bug only after five days) and fertile (bearing two juveniles). He then added several anecdotes about other individual sphaeriids found attached to the digits of amphibians, and finished with the charming observation that "my son Francis, while fishing in the sea off the shores of North Wales, noticed that mussels were several times brought up by the point of the hook."

Darwin concluded his 1882 work, "there can, I think, be no doubt that living bivalve shells must often be carried from pond to pond, and by the aid of birds occasionally even to great distances." This point may seem a bit trivial to us today, perhaps even quaint (7). But Darwin’s central thesis, that all these creatures have diverged from a single common ancestor, required that they have originated at a single point, and dispersed throughout the world. If a convincing case could be built for freshwater mollusks, surely to be ranked among the most disadvantaged of the world’s dispersers, perhaps the remainder of the worldwide biota might fall into line.

There’s an interesting postscript to the story of Charles Darwin’s career as a freshwater malacologist. The "Mr. W. D. Crick of Northampton" who sent Darwin his report of the fingernail clam pinched on the water bug leg was Walter Drawbridge Crick (1857-1903), the grandfather of Francis H. C. Crick, who (with James Watson & Maurice Wilkins) shared the 1962 Nobel Prize for elucidating the structure of DNA (8).

At the outset of this essay, I characterized Charles Darwin as “the last complete biologist.” Chief among the reasons that there can be no more such protean figures must be the 20th century explosion of molecular biology, which has expanded our discipline in directions Darwin could never have imagined. It is a source of some inspiration to me that one can trace a path from Darwin to DNA through the great man’s last paper, and the humble discipline of freshwater malacology.

Notes

(1) Yes, Chapter 1 of Darwin’s “Voyage of the Beagle” included a passing note about “infusoria” (primarily diatom frustules) in dust accumulated while on shipboard.

(2) I’ve taken a bit of license with this paragraph. Darwin had a couple publishing credits prior to his (1839) “Voyage,” and several posthumous papers after his 6 April 1882 paper on freshwater bivalve dispersal. Darwin’s complete bibliography, including PDF downloads of the papers mentioned here, is available at Darwin Online.

(3) Dytiscus is a genus of large, predatory water bugs. Although spending the great majority of their lives swimming gracefully through the water column, they may on occasion take to the wing, flying like balsa-wood airplanes with old rubber bands.

(4) Darwin, C. (1878) Transplantation of shells. Nature 18: 120-121.

(5) Darwin, C. (1882) On the dispersal of freshwater bivalves. Nature 25:529-530.

(6) The genus Cyclas has since been synonymized under Sphaerium. Today this common European "fingernail clam" is generally referred to as Sphaerium corneum.

.

(7) It is not, however. See the classic paper:W. J. Rees (1965) The Aerial Dispersal of Mollusca, Proc. Malac. Soc. London 36: 269 - 282.

(8) We must acknowledge an article in the February 2009 issue of National Geographic for calling our attention to this remarkable coincidence: Ridley, M. (2009) Modern Darwins. National Geographic 215: 56 - 73.

The Freshwater Gastropods of Indiana

Editor’s Note. This essay was subsequently published as: Dillon, R.T., Jr. (2019d) The Freshwater Gastropods of Indiana.  Pp 215 - 218 in The Freshwater Gastropods of North America Volume 4, Essays on Ecology and Biogeography.  FWGNA Press, Charleston.

Kudos go to our colleague Mark Pyron and his students Jayson Beugly, Erika Martin and Matthew Spielman for their thorough survey of the freshwater gastropods of Indiana, appearing in the most recent American Malacological Bulletin (1). No big surprises here, but a job well done!

Physiographically, Indiana can be divided into three regions from north to south: the Great Lakes plains, the till plains, and the southern low plateau (which glaciation did not reach.) Rivers in a northern sliver of the state flow north to the Great Lakes, but the great majority of the state drains south through the Kankakee/Illinois or the Wabash/Ohio systems. Prehistorically the entire state would have been covered with mixed woodland, grassland, and wetland, but today 98% of Indiana has been converted to agriculture. Industrial regions have sprung up in the north and central.

Goodrich & van der Schalie (2) published a nice survey of the entire molluscan fauna of Indiana in 1944, and both the University of Michigan Museum of Zoology and the Ohio State Museum have substantial Indiana holdings today. Pyron's initial review of these historical records led him to expect a freshwater gastropod fauna of 39 species, nothing (to my eye) especially rare or surprising. He and his students then designed a survey of 123 ponds, lakes, rivers and streams around Indiana, covering all drainages and physiographic provinces, revisiting 86 sites for which historical data were available. They documented 36 freshwater gastropod species (3) – missing several that might have been expected from historical records, but discovering a few species not previously listed. Pyron concluded that "the majority of the freshwater gastropod taxa in Indiana are of local conservation concern."

This is the third squarish Midwestern state to be surveyed in recent years, and one is tempted to begin looking for patterns. Shi-Kuei Wu and colleagues (4) published a big monograph of the Missouri freshwater gastropods in 1997 which, boiling off 17 synonyms, listed 39 valid species. Our colleague Tim Stewart (5) had a nice 2006 paper in the AMB reporting 46 species of freshwater gastropods in Iowa (6). Both the Missouri and the Iowa inventories relied on historical records, and in fact, Tim developed his Iowa list without fresh field surveys of any sort. Thus the fair comparison would be with the total fauna of Indiana developed by Pyron - historic as well as modern - a list of 40 species (7).

The figure at left above is a Venn diagram of Midwestern States, using rectangles rather than circles, each state oriented geographically and scaled in proportion to its surface area (8). The most striking feature of this diagram to my eye is an effect of latitude (or perhaps physiography), making the Indiana/Iowa pair far more similar than either state is to Missouri.

Indiana has four unique species - almost entirely pleurocerids (including Leptoxis praerosa, Pleurocera canaliculata, and Pleurocera semicarinata "obovata"). Iowa has five unique species - almost entirely northern pulmonates (including Lymnaea catascopium "emarginata", L. megasoma, L. haldemani, and Physa skinneri). The two states share an impressive 35 freshwater gastropod species – 20 that also occur in Missouri and 15 that do not.

The Missouri fauna is characterized by 12 unique species of freshwater gastropods, including three pleurocerids and seven endemic hydrobiids of the Ozark Plateau. But as its diversity rises by extension into a new physiographic province, Missouri's fauna also declines by the subtraction of quite a few northern elements common in Iowa and Indiana, for example Lymnaea stagnalis, Helisoma campanulata, Aplexa and several Valvata. Thus although the largest of the three states, in net effect Missouri finishes with the shortest faunal list.

Meanwhile, back in Muncie, I'm pleased to report that our colleague Mark is busily developing an FWGNA-style website to disseminate the results of his Indiana survey more fully. And he’s thinking about collaborating and expanding this effort into the surrounding states of the upper Mississippi watershed. Exciting developments, to which we can all look forward!

Notes

(1) Pyron, M., J. Beugly, E. Martin, and M. Spielman (2008) Conservation of the freshwater gastropods of Indiana: Historic and current distributions. Am. Malac. Bull. 26: 137-151. [download PDF]

(2) Goodrich, C. and H. van der Schalie (1944) A revision of the Mollusca of Indiana. Am. Midl. Natur. 32: 257-326.

(3) Pyron's estimate of 36 extant species included four species reported by E. H. Jokinen (2005) Pond mollusks of Indiana Dunes National Lakeshore: Then and now. Am. Malac. Bull. 20: 1 - 9.

(4) Wu, S-K, R. D. Oesch and M. Gordon (1997) Missouri Aquatic Snails. Missouri Department of Conservation, Jefferson City. Natural History Series 5: 1 - 97.

(5) Stewart, T. W. (2006) The freshwater gastropods of Iowa (1821-1998): Species composition, geographic distributions, and conservation concerns. Am. Malac. Bull. 21: 59-75.

(6) Stewart listed 49 species, but here I combine Lymnaea exilis under L. palustris, Helisoma truncata under H. trivolvis, and Laevapex diaphanus under L. fuscus.

(7) Pyron's complete Indiana list included 41 species, but again I have combined Lymnaea exilis under L. palustris.

(8) Indiana 36,000 mi2, Iowa 56,000 mi2, Missouri 70,000 mi2.