Influential Publications in Freshwater Gastropod Conservation

Back on April 22 I forwarded the following email from our good friend Bob Hershler to the FWGNA group:

We are preparing a paper on “Molluscan conservation over the past 50 years” for the upcoming UNITAS conference and toward that end we are asking the malacological community to help us identify the most important/influential publications on the subject between 1960-2010. If you have the time and interest, please send us a short list of no more than 5 publications that you consider to be in this category. Thanks very much in advance!

Bob Hershler (hershlerr@si.edu)
Rob Cowie (cowie@hawaii.edu)

Bob indicated that he will be accepting nominations through the first week of May. So there's still a bit of time to send him your suggestions, if you hurry.

I myself struggled with this assignment. Freshwater gastropod faunas are fundamentally regional, as are we researchers who study them, as are the conservation communities that rise to their defense, as are state agencies, as indeed even is the US Fish and Wildlife Service. There is no reason to expect that an inventory of gastropod species facing extinction from impoundments in Alabama, for example, should have any influence on livestock degradation of springs in New Mexico, no matter how compelling.

So I decided to subdivide my nominations by region. As of 5/2010, the US endangered species list includes 9 freshwater gastropods from the Mobile Basin of Alabama, 5 from the arid southwest, 5 from the Snake River, 2 from Tennessee, and 1 from Missouri. My initial idea was to gauge the "influence" of candidate publications by examining the literature cited sections of the entries in the Federal Register in which these 22 species were proposed, perhaps according more importance to the earlier references than to the later ones.

But a dichotomy immediately presented itself. Here in the East, the publications that seem to have influenced gastropod conservation all advance the argument, "Species X was common, and is now rare." So the proposals in the Federal Register for Alabama and Tennessee species cite 19th-century works of taxonomy, 20th-century alarms of a general nature, and unpublished status reports documenting the specific conservation situation. But in the West, species arrive rare. The Federal Register cites 20th-century works of taxonomy leading directly to unpublished status reports, skipping the general calls to alarm.

Ultimately I decided not to offer any recommendations for The West. I have very little experience in western regions, and (from the outside) was unable to identify any publications of even regional influence. Within the East I have divided my nominees into the Tennessee region, the Alabama region, and a special category from the Northeast.

First Place, Tennessee Region
Stansbery, D. H. (1970) Eastern Freshwater Mollusks (I) The Mississippi and St. Lawrence River Systems. Malacologia 10: 9-22.

This was the most lengthy contribution to the "Symposium on Rare and Endangered Mollusks of North America" organized by Arthur Clarke for the 1968 AMU meeting in Corpus Christi. Clarke edited the proceedings of the entire symposium for publication as a unit in the 1970 Malacologia 10: 3 - 56. That symposium featured contributions by 14 prominent malacologists of the day (1), and might justifiably be cited as a single work.

Dave Stansbery was primarily a unionid worker, but directed some attention in his paper to the status of pleurocerid populations in the eastern and central regions of North America. He specifically highlighted Io fluvialis ("A few relic populations remain") and Athearnia ("Eurycaelon - a few populations of at least one species yet survive.") In subsequent papers (2) Stansbery went on to document the elimination of Io from the North Fork Holston River, its type locality.

As the symbol of the American Malacological Society, Io fluvialis is literally "iconic." The alarm bell rung by Stansbery in 1970 was followed by the successful transplant efforts of Ahlstedt (3) ultimately keeping Io off the endangered species list (4).

Second Place, Tennessee Region
Bogan. A. E., & P.W. Parmalee. 1983. Tennessee’s Rare Wildlife, Volume II: The Mollusks. Tennessee Wildlife Resources Agency, Nashville. 123 pp.

The only Tennessee drainage freshwater gastropods to reach the Federal list have been Pyrgulopsis ogmorhaphe and Athearnia anthonyi, both in 1994. A review of the 5Aug93 issue of the Federal Register in which those two species were formally proposed for endangered status shows the work of Bogan and Parmalee cited prominently. This is certainly a much more complete work than that of Stansbery, although appearing later on the scene.

First Place, Alabama Region
Stein, C.B. 1976. Gastropods. Pp. 1-41 in Endangered and Threatened Plants and Animals of Alabama. H. Boschung (ed.). Bull. Alabama Museum of Natural History 2: 21- 41.

The first freshwater gastropod to enter the Federal Endangered Species list was Tulotoma magnifica in 1991. The review of Stein (1976) appears as the primary (published) reference in the 11July90 Federal Register proposing that endangered status. And even though at least four additional calls to alarm on behalf of the Mobile Basin fauna have been issued more recently (5), Stein's work may still be the most thorough.

Second Place, Alabama Region
Athearn, H. D. (1970) Discussion of Dr. Heard's paper. Malacologia 10: 28-31.

A batch of six Mobile Basin gastropods were added to the Federal list in 1998. The Federal Register of 17Oct97 cited six references in support of the statement that "During the past few decades, publications in the scientific literature have primarily dealt with the apparent decimation of this fauna" - Goodrich 1944, Athearn 1970, Heard 1970, Stein 1976, Palmer 1986, and Garner 1990. The work of Goodrich 1944 is a bit old for our fifty-year window, but the Athearn 1970 / Heard 1970 pair certainly does seem to have had an impact.

These papers were both contributed to that same (1968) symposium that also featured the Stansbery paper cited above. Bill Heard’s paper, entitled "Eastern freshwater mollusks, the South Atlantic and Gulf Drainages," was rather vague and general. But the "Discussion” by Herb Athearn, appearing in print as a simple four page list of "now rare and endangered, or possibly extinct" species, seems to have had a significant influence on Carol Stein's more complete review and the regulations that followed in the 1990s.

Northeast
Harman, W. N. & J. L. Forney (1970) Fifty years of change in the molluscan fauna of Oneida Lake, New York. Limnology & Oceanography 15: 454-460.

The quality of the science in all four of the works cited for Tennessee and Alabama above is anecdotal at best. In fact, the papers of Stansbery and Athearn do not even rise to the level of the anecdote. For their 1970 paper in L&O, by contrast, Harman and Forney rigorously resampled Oneida Lake at the same spots originally sampled by F. C. Baker in 1917 (6), using similar gear. They documented significant reductions in gastropod abundance, species richness and diversity, and striking faunal shifts with the introduction of the invasive Bithynia tentaculata.

Harman and Forney’s work inspired me as a graduate student to reanalyze Baker’s data for a paper I published in The American Naturalist in 1981 (7), carrying forward to Chapter 9 of the book I published in 2000 (8). Harman also followed his 1970 study with a third study in 1992-95, documenting another 31% reduction in species richness with the introduction of zebra mussels (9).

Nominally driven to extinction in the 50 years between 1917 and 1967 were three nominal species nominally endemic to Oneida Lake, Amnicola bakeriana, A. clarkei, and A. oneida. Henry Pilsbry differentiated these three taxa from other much more widespread hydrobiids on the slenderest of threads (10). Nevertheless, the phantom New York hydrobiids of Baker and Pilsbry are no less valid than the phantom Alabama pleurocerids that Athearn listed without comment down the left margin of Malacologica Volume 10 in 1970 (11).

But Harman’s call to alarm has been of no consequence to freshwater gastropod conservation whatsoever. That a rigorous work of scientific research should disappear completely from the public conscience, while an unsubstantiated faunal list reaches the Federal Register to impact the laws of the land, should surprise none of my faithful readership (12). Science and Public Policy are two entirely different things.

Pushing on in the former, nonetheless,
Rob

Notes

(1) Stansbery, Clarke, Heard, Athearn, Dwight Taylor, Murray, Clench, Dundee, Allyn Smith, Abbott, Rosewater, Keen, Emerson, and Joe Morrison.

(2) Stansbery, D. H. (1972) The mollusk fauna of the North Fork Holston River at Saltville, Virginia. Bull. AMU 1972: 45-46. Stansbery, D. H. & W. J. Clench (1974) The Pleuroceridae and Unionidae of the North Fork Holston River above Saltville, Virginia. Bull. AMU 1974: 33-36. Stansbery, D. H. & C. B. Stein (1976) Changes in the distribution of Io fluviatilis in the upper Tennessee River system. Bull AMU 1976: 28-33.

(3) Ahlstedt, S. A. (1991) Reintroduction of the spiny riversnail Io fluvialis into the North Fork Holston River, southwest Virginia and northeast Tennessee. Amer. Malac. Bull. 8: 139-142.

(4) The reintroduction of Io into the NF Holston depended on much more than a few papers in the Bulletin of the AMU. The snails (and indeed, most of the benthic fauna of the river) were eliminated by pollution from the Olin-Mathieson Chemical Company in Saltville, which was closed by the EPA in 1971-72. Our good friend Steve Ahlstedt tells me that his Io transplant project was an outgrowth of water quality monitoring projects that started in the mid-1970s with mussels in barbeque baskets.

(5) Mobile Basin I: Two Pleurocerids Proposed for Listing [24Aug09]

(6) Baker, F. C. (1918) The productivity of invertebrate fish food on the bottom of Oneida Lake, with special reference to mollusks. NY State Coll. Forestry Tech. Publ. 9. 264 pp.
For more about this remarkable man and his work, see
The Legacy of Frank Collins Baker [20Nov06]

(7) Dillon, R.T. (1981) Patterns in the morphology and distribution of gastropods in Oneida Lake, New York, detected using computer-generated null hypotheses. American Naturalist 118: 83-101. [PDF]

(8) Now available in paperback! [Dillon 2000]

(9) Harman, W. N. (2000) Diminishing species richness of mollusks in Oneida Lake, New York State, USA. Nautilus 114: 120-126.

(10) Pilsbry, H. A. (1918) New species of Amnicolidae from Oneida Lake, New York. pp 244-246 in F. C. Baker, cited in (6) above. We'll never know, but from Pilsbry's descriptions it looks to me like Amnicola bakeriana may be a synonym of A. limosa, Amnicola clarkei is Lyogyrus granum, and Amnicola oneida is Marstonia lustrica.

(11) See my four-part series on the Mobile Basin pleurocerids:
I. Two Pleurocerids Proposed for Listing [24Aug09]
II. Leptoxis Lessons [15Sept09]
III. Pleurocera Puzzles [12Oct09]
IV. Goniobasis WTFs [13Nov09]

(12) See for example: Red Flags, Water Resources, and Physa natricina [12Mar08] and references cited therein.

TRUE CONFESSIONS: I Described a New Species

Editor's Note.  This essay was subsequently published as: Dillon, R.T., Jr. (2019b) TRUE CONFESSIONS: I described a new species.  Pp 193-198 in The Freshwater Gastropods of North America Volume 2, Essays on the Pulmonates.  FWGNA Press, Charleston.

... or, to deflect at least a fraction of the calumny, two accomplices and I described a new species. A pdf of the recent description of Physa carolinae by Wethington, Wise, and Dillon can be downloaded from note (1) below.

The existence of dark, slender populations of Physa in the Charleston area was first called to our attention in the 1980s by the late Julian Harrison, a colleague on The College faculty, primarily a herpetologist but an excellent all-round naturalist. The sample he brought us came from a shallow, swampy pond on James Island, in suburban Charleston. I told him these were simply "Physa heterostropha," which is what I called all the local Physa populations twenty years ago.

A couple years later Amy Wethington and I discovered a second population of slender, dark Physa in an agricultural ditch on Johns Island, about 10-15 km south of the city. We were working on a population genetic study designed to evaluate barriers to dispersal among sea islands (2), and needed to find a Physa population in an extensive region of sod farms to complete our (rather tightly specified) sampling grid. On the map, this part of Johns Island looked most unpromising. Sod farms are heavily fertilized and irrigated, ditched and drained into collecting ponds, brutally hot in the summer and exposed in the winter. But sure enough, in a damp and weedy ditch in the middle of Johns Island [right, below], Amy and I found another population of strikingly dark, slender Physa.

Intriguingly, this dark slender morphology seemed to have a strongly heritable component. Lab lines of the “Johns Island Physa” retained their distinct appearance to the second and third generations in culture. In the mid-1990s I did some experiments (as yet unpublished, shame on me) to estimate the heritability of shell shape (six linear measures) by regressing F1 hybrids between the Johns Island line and our standard (fatter) Physa lines on their mid-parent values. The heritability of shell morphology was strikingly high, but I digress.

The F1 hybrids derived from that experiment failed to reproduce. In retrospect, these observations probably influenced the first set of studies Amy and I designed to test reproductive isolation in Physa (3). We studied two populations of Physa heterostropha, two populations of P. integra, and two populations of P. acuta because (we imagined) that we’d find some reproductive isolation within species, as well as reproductive isolation between nominal species. We didn’t find any reproductive isolation among any of these six populations, of course, prompting us to synonymize most of the world’s Physa populations under the single nomen, Physa acuta.

Wait, wait! Does Rob Dillon have the arrogance to assert that dozens (scores?) of specific physid nomina (4) recognized by the entire community of systematic biologists around the world for 200 years are all synonyms of a single, variable, cosmopolitan Physa acuta, while in some ditch ten kilometers south of Charleston lives a bona fide undescribed species that only Rob Dillon can recognize? Let’s back up and get a fresh start.

The taxonomy of the North American Physidae in currency when Amy and I began our research program in the late 1980s was that of George Te, as reproduced in Burch’s "North American Freshwater Snails." Had I sent my dark, slender Physa to Te while he was still active in the 1970s, I feel fairly certain that he would have identified them as "Physella hendersoni" (5), the type locality of which is in Yemassee, SC, just 80 km west of Charleston. Burch's figure 677, labeled "Physella (Costatella) hendersoni ssp," does indeed appear to depict a slender shell quite similar to that borne by our Johns Island population.

But in another of those serpentine turns for which freshwater malacology is so famous, “hendersoni” was originally described by Clench (1925) as a subspecies of Physa pomilia Conrad (1834). Te considered pomilia to be a subspecies of P. heterostropha while holding hendersoni distinct. Working with snails sampled from their type localities, however, our 2007 breeding studies demonstrated both that hendersoni and pomilia are conspecific, as Clench originally suggested, and that pomilia/hendersoni most certainly is reproductively isolated from heterostropha/acuta (6).

And our dark, slender physids (which we began calling "Physa Species A" about ten years ago) are reproductively isolated both from pomilia/hendersoni and from acuta/heterostropha. The paper immediately preceding the description of these populations as Physa carolinae is a Dillon (solo) work documenting F1 hybrid sterility between carolinae and acuta, and both sexual isolation and apparent hybrid inviability between carolinae and pomilia (7).

So yes, as embarrassing as it looks – the research group responsible for synonymizing the physid fauna of the entire continent from about 40 nominal species down to maybe ten (8) is now asserting that we have discovered a Physa species overlooked by everybody, in our own back yards.

Physa carolinae seems seasonally common and widespread throughout the Atlantic Coastal Plain, ranging at least from Virginia to Georgia. We do not have any original field observations further south, but a glance through the collections of the Florida Museum of Natural History a couple years ago suggested to me that Physa carolinae may also be widespread in Florida, museum lots generally catalogued under the specific nomen "hendersoni."

Throughout its range, P. carolinae is most commonly found in swamps, ditches, and other waters of an intermittent or vernal character. It seems to be a southeastern ecological analogue of Aplexa – the two taxa converging on each other in habitat, life history, and morphology.

This Saturday just past Amy, John Wise, and I were featured in the Charleston newspaper as "Snail Sleuths - CofC Researchers Find Lowcountry Species" (9, 10). In addition to some cutesy quotes about the pace of snail research being - well - slow, I found myself saying something like this to the reporter: "We send scientists all over the world, and we don't know the slugs under our own trash cans." If anybody on this list is aware of any funding agencies that might be responsive to such an appeal, please bring them to our attention at your earliest convenience.

And keep in touch,
Rob

Notes

(1) Wethington, A.R., J. Wise, and R. T. Dillon (2009) Genetic and morphological characterization of the Physidae of South Carolina (Pulmonata: Basommatophora), with description of a new species. The Nautilus 123: 282-292. [PDF]

(2) Dillon, R.T., and A.R. Wethington (1995) The biogeography of sea islands: Clues from the population genetics of the freshwater snail, Physa heterostropha. Systematic Biology 44:401-409. [PDF]

(3) Dillon, R. T., A. R. Wethington, J. M. Rhett and T. P. Smith. (2002) Populations of the European freshwater pulmonate Physa acuta are not reproductively isolated from American Physa heterostropha or Physa integra. Invertebrate Biology 121: 226-234. [PDF]

(4) Wethington, Wise & Dillon listed 19 nomina in their P. acuta synonymy, including heterostropha, integra, the western virgata, and the more tropical cubensis. Also listed was P. natricina, about which I offered an entire essay on 12Mar08.

(5) I swapped several letters with George Te in 1976, while I was still an undergraduate at Virginia Tech. He identified the Physa acuta I sent him from the New River as "P. hendersoni," and my Physa gyrina as "P. pomilia."

(6) Dillon, R. T., J. D. Robinson, and A. R. Wethington (2007) Empirical estimates of reproductive isolation among the freshwater pulmonates Physa acuta, P. pomilia, and P. hendersoni. Malacologia 49: 283 - 292. [PDF]

(7) Dillon, R. T. (2009) Empirical estimates of reproductive isolation among the Physa species of South Carolina (Pulmonata: Basommatophora). The Nautilus 123: 276-281. [PDF]

(8) Wethington, A. R. & C. Lydeard (2007) A molecular phylogeny of Physidae (Gastropoda: Basommatophora) based on mitochondrial DNA sequences. J. Molluscan Stud. 73: 241 - 257. [PDF]

(9) Snail Sleuths: CofC researchers find lowcountry species
Charleston Post & Courier 3April2010

If the link above expires, go to the FWGNA archives:
Post&Courier3Apr2010

(10) And I'm now starring on YouTube! Check it out:
http://www.youtube.com/watch?v=wTzgv5sxFRQ

The Hazards of Unprotected Malacology

On March 13, nature writer Nick Mirro posted the following query to the MOLLUSCA listserver:

I hate to show my ignorance here, but… Are there any or many North American fresh water gastropod or bivalve species that could potentially transmit disease to human by skin (hand) contact? I am asked this question all the time and am not confident in my stock answer, which is, “no but wash your hands anyway.” We are in north central Texas. Thanks.

Here, for the general entertainment of our group, is my reply:

--------------
Dear Nick,

No, you're not "showing your ignorance!" That's such an interesting question, I'm going to answer it four times.

1) Nah, don't worry about it. I've hand-collected freshwater mollusks all over North America for 40 years, and never given it a second thought.

2) Well, actually, some very widespread freshwater mollusk species can thrive in polluted environments. I've seen strikingly high densities of Physa acuta, Lymnaea humilis, and the pisidiid clam Musculium transversum downstream from sewage treatment plants. (Unionids, not so much!) It might be a good idea to wash your hands after pulling anything from such waters - rocks, bottles, beer cans, snails or clams included. There was a little scare in the Myrtle Beach area a summer ago when state wildlife officials advised residents of a trailer park not to handle Pomacea insularum introduced into a nasty drainage pond in their neighborhood. See my blog post of 14Aug08* to read more.

3) Several years ago I visited Northern Michigan to sample Physa parkeri** from the lovely waters of Douglas Lake, at the University of Michigan Biological Station. I made my collection in a one-gallon thermos jug, planning to transport the sample back to Charleston alive. The next morning I was disappointed (but perhaps not terribly surprised) to discover that quite a few individuals had expired. So I reached into the jug (repeatedly) to remove the dead individuals for preservation, leaving the live ones undisturbed. Here's the case of schistosome dermatitis ("swimmers itch") that resulted.

4) Nah, don't worry about it. I never do.

Cheers,
Rob

Notes


*Two dispatches from the Pomacea front [14Aug08]

**Physa parkeri turned out to be an ecophenotypic variant of Physa gyrina. See Dillon & Wethington (2006) The Michigan Physidae revisited: A population genetic study. Malacologia 48: 133-142. [PDF]

Grand Opening!

It's not unusual for retail stores to open their doors for business, operate for a few weeks, and then announce a "Grand Opening." I'm not sure about the rationale for this practice, but welcome to the Grand Opening of the FWGNA Blog! Doing business since July, 1998.

For any newcomers who might stumble onto this post - the Freshwater Gastropods of North America project was born at the first World Congress of Malacology in Washington, 12 years ago this summer. Our objective has always been to survey the entire continent for freshwater snails, by any means necessary. Four states mostly done as of February 2010! What a team!

In any case, very early in the effort I fell into the habit of sending mass emails to an ever-growing addressbook of colleagues - 186 at last count - recently about once per month*. Often these messages have been simple news items about upcoming meetings, grants, employment opportunities, or whatever. But increasingly I've found myself reviewing and reporting on the current literature, offering opinions on taxonomic questions, and pontificating on invasive species, endangered species, and matters at the interface between science and public policy.

Clearly we've needed a medium to open up a better conversation for a long time. I'm not sure why I didn't migrate to the blog format years ago.

An important (although perhaps secondary) benefit of modern blogging is the convenience of the indexing function. So over the last couple weeks I've uploaded (from the "FWGNA Archives") the great majority of my old email posts, "tagging" them as I did with the brief descriptors you see listed at right. And I imagine you've noticed the Google-powered search box. It may take a while for the Google webcrawlers to find this tiny corner of the internet and "populate" that search box, but eventually it should become a helpful tool.

And now its up to all of us to give those web-crawlers something to feed on! Regarding comments - I am advised that, unless I moderate this blog, unscrupulous agents will use the blank spaces provided to advertize viagra. But you do not need a Google account to comment. Type your message in the comment box, and choose "name" in the "select profile" box, or even "anonymous" if you want. I'll get an email alerting me that a comment needs my approval, and do so promptly.

Looking forward to it,
Rob


*I'm still planning to maintain my email list, and I guess I'll continue to send monthly emails. But they'll be short - probably just a title and a link to the blog.

Okay, okay! I'll start a blog!

To the FWGNA group: My message of 18Dec09 regarding the community consequences of Bellamya invasion seems to have struck a chord. In addition to the scattering of "atta-boys" I often receive (and always appreciate), last month's post attracted four comments that seem substantive enough to share. John Havel (of Missouri State) wrote me with several insights regarding invasion biology in lakes (as applied to Bellamya in particular), David Campbell (Alabama) offered taxonomic comments, and both Jeremy Tiemann (Illinois Natural History Survey) and Bob Prezant (Montclair) suggested additional references. I have appended (slightly edited) versions of the emails I received from these four gentlemen to the end of my 18Dec09 post. When I first started sending messages to the FWGNA group back in July of 1998, I had never heard the word, "blog." But I just googled-up Wikipedia, and apparently the term itself dates to 1994. The first "hosted blog tools" became available in 1999. In recent years, the internet has become something more like a community, for better or worse. I have always, at least occasionally, posted your comments regarding my monthly essays in the form of a "P.S." in the FWGNA archives. But this is an old-timey pairwise approach, where I say something to you, and then you say something to me. The internet now seems to have developed to a point where everybody expects to talk to everybody else, as a community. OK, okay - I'll start a blog. I don't know how I'll go about doing this, or when the transformation will occur. But the advantages of group communication are as obvious to me as they must be to everybody I'm talking to right now, pairwise. So we'll keep in (better) touch, Rob

Community Consequences of Bellamya Invasion

Editor’s Note – This essay was subsequently published as: Dillon, R.T., Jr. (2019d)  Community consequences of Bellamya invasion.  Pp 47 - 53 in The Freshwater Gastropods of North America Volume 4, Essays on Ecology and Biogeography.  FWGNA Press, Charleston.

I dearly love experiments. Does it seem to anybody else on this list that, over the last 20-30 years, the experiment is going out of style? In any case, the recently published research results of Pieter Johnson, Chris Solomon, and their colleagues on the community effects of Bellamya (1) invasion, which include both experimental and field components, arrive as especially welcome contributions to our (surprisingly slender) file on the biology of invasive viviparids.

Bellamya populations (2) seem to have appeared in the Northern Highlands lake district of Wisconsin sometime in the 1950s. Johnson and his colleagues (3) conducted an 8-week experiment in a set of 24 outdoor “mesocosms” containing 1,000 of water from nearby Sparkling Lake, a clean sand/gravel substrate (inoculated with lake mud), two cinder block “refugia,” and 45 individuals each of Physa gyrina, Lymnaea stagnalis, and Helisoma trivolvis. Eight of the mesocosms received 45 Bellamya, eight received a pair of crayfish (4), eight received both Bellamya and crayfish, and eight were held as controls.

The most striking result of these experiments was that the populations of Physa and Lymnaea grew in the absence of Bellamya, but declined in the presence. The control Physa roughly doubled in population size over the 8 weeks, while the control Lymnaea roughly doubled in wet mass, although apparently did not reproduce (5). But all pulmonate populations declined by all measures in the Bellamya treatments. Clearly the invasion of Bellamya through the lakes of Northern Wisconsin should have negative effects on the native freshwater gastropods, right?

Well, of course it’s more complicated than that. The Helisoma populations declined in both biomass and abundance (5) in all mesocosms, including the controls. Whether the Helisoma were outcompeted by the Physa and Lymnaea, or whether these mesocosms were simply unsuitable habitat for Helisoma, we'll never know. My intuition suggests to me that if the researchers had floated some macrophytic vegetation on the surface of their mesocosms, their Helisoma populations would have been fine (6). The problem is that the experiments of Johnson and colleagues show Helisoma going to extinction in the absence of Bellamya just as clearly as they show Physa and Lymnaea going to extinction in the presence (7). As much as I love experiments, a 5’ x 5’ structural foam plastic tank and a lake are two entirely different things.

Who could disagree? Certainly not our colleagues in Wisconsin. Thus in a companion study, Chris Solomon and a gang of four (including yours truly) surveyed 42 lakes in northern Wisconsin, roughly half of which had been invaded by Bellamya and half not, collecting a great variety of environmental measures in the process (8).

We found evidence of positive correlations between the presence of Bellamya and several general measures of lake productivity, such as conductivity and Secchi turbidity, but very little evidence of an effect of Bellamya on the native freshwater gastropod fauna. At neither the site level nor at the lake level could we find any evidence that Bellamya presence or abundance had any effect on the native freshwater gastropod community at all.

The absence of any significant results whatsoever neatly confirms my hypothesis, of course. Casting an eye back through the FWGNA archives, it looks as though I’ve authored fully 13 previous posts on invasive species, primarily Pomacea, Potamopyrgus, and Bellamya, with other viviparids and Bithynia making cameo appearances. And it may be recalled that I am an advocate of the “empty niche” hypothesis, which dates me back to the 1970s with most embarrassing accuracy.

Essentially, I think that the two best predictors for the success of a potential invasion are that the invading population must be weedy and different (9). Invaders must be adapted to the new environment they are invading, of course, while ecologically different from the native inhabitants – the more different, the better.

The gigantic, filter-feeding, ovoviviparous Bellamya is indeed strikingly different from all the other elements of the freshwater gastropod community native to northern Wisconsin. Hence I would not expect to uncover any competitive effects, and feel quite validated that we did not find any.

But I hasten to add two asterisks. First, populations of four different species of viviparids inhabit the lakes of northern Wisconsin, three of which are gigantic, filter-feeding, ovoviviparous invaders: Bellamya chinensis, B. japonica, and Viviparus georgianus. That our distributional data returned no evidence of a negative relationship within this subset, over 197 sites in 42 lakes, does indeed seem to suggest that our methods may have been too weak to detect even bona fide competition, where it occurs.

Second, a special challenge attends the selection of any invasive species for a study of population biology. What would make the researcher think that any such population has reached the carrying capacity of its environment? Competition cannot begin until some resource becomes limiting. If both Bellamya and Viviparus populations are still growing and spreading through northern Wisconsin in 2009, there is no reason to imagine that either will have any effect on the other.

And in fact, our analysis did return evidence of correlations between Bellamya presence and such measures of disturbance such as boat landings and shoreline housing. This implies to us that Bellamya populations may indeed be actively growing and spreading even in northern Wisconsin, where the invasion may have been ongoing for as much as 50 years.

I conclude with a call for additional research (10). This is a button you have rarely seen me push in this series of essays, both because it is trivially obvious to me that we need additional research on all aspects of freshwater gastropod biology, and because I try not to preach to the choir.

But where other people see "invasive species," I see "model organism." We have been greatly enriched, for example, by a huge volume of first-rate research on Pomacea in recent years (11), and that literature is huge (12). Meanwhile I haven't seen more than a couple papers published on even the most basic aspects of the life history of Bellamya, in total, over the 100-year history of the North American invasion (13). And three paragraphs ago I found myself offering an hypothesis regarding carrying capacities of invasive viviparids without a single estimate of population size, even static, ever taken anytime, anywhere. As easy as invasive viviparids are to sample, sitting on clean sand at the bottom of bathtub reservoirs? Shame on us all!

Keep in touch, everybody!
Rob

Notes
(1) I follow Smith (2000) in preferring the (internationally-recognized) generic nomen "Bellamya" over the (provincial) "Cipangopaludina." See the FWGNA page on B. japonica for details and references.

(2) Wisconsin populations are almost entirely Bellamya chinensis. I did identify B. japonica in five (of 42) lakes surveyed, which were lumped with B. chinensis for analysis. That's B. chinensis on the left, and B. japonica on the right.


(3) Johnson, P. J., J. D. Olden, C. T. Solomon, and M. J. Vander Zanden (2009) Interactions among invaders: community and ecosystem effects of multiple invasive species in an experimental aquatic system. Oecologia 159: 161-170.

(4) The crayfish were the invasive Orconectes rusticus. Those results were interesting as well, but don’t bear directly on the subject of this essay.

(5) Pulmonate juveniles are born at approximately 1 mm shell length. The sampling problems of finding such “speck babies” in a 1,000 liter mesocosm with sand and cinder blocks should be obvious to everybody. Thus I strongly suspect the “pulmonate abundance” figures reported by Johnson and colleagues are systematic underestimates.

(6) Helisoma is certainly quite commonly observed on floating vegetation. Any sort of additional habitat along these lines would certainly have benefited all three pulmonate populations.

(7) And if there’s a crayfish in the lake, all pulmonate populations are immediately doomed.

(8) Solomon, C. T, J. D. Olden, P. T. J. Johnson, R. T. Dillon and M J. Vander Zanden (2010) Distribution and community-level effects of the Chinese mystery snail (Bellamya chinensis) in northern Wisconsin lakes. Biological Invasions 12: 1591 - 1605. [PDF] 476kb.

(9) "Invaders Great and Small" Post of September '08.

(10) This should not be construed as a call to sequence two genes from single individuals sampled from 40 imaginary viviparid species in a vain attempt to reconstruct evolutionary events of 100 million years ago, while remaining arrogantly clueless regarding the basic population genetics of even one crappy pond full of crappy snails today.

(11) "Ampullariids star at Asilomar" Post of August '05.

(12) "Review: Global Advances in Golden Apple Snails" Post of May '07.

(13) Stanczykowska, A, E. Magnin and A. Dumouchel (1971) Etude de trois populations de Viviparus malleatus (Reeve) de la region de Montreal. I. Croissance, fecondite, biomasse et production annuelle. Can. J. Zool. 49: 1431-1441. Jokinen, E.H. (1982) Cipangopaludina chinensis (Gastropoda: Viviparidae) in North America, review and update. Nautilus 96: 89-95. Therriault, T. W. and E. Kott (2002-3) Cipangopaludina chinensis malleata (Gastropoda: Viviparidae) in southern Ontario: An update of the distribution and some aspects of life history. Malac. Rev. 35-36: 111-121.

Comments
(1) From John Havel JohnHavel@MissouriState.edu

Hi Rob,

Since I’m a newcomer to snail research (although an old hand at invasions), I was hesitant to reply to all. So, below are my comments on your most-interesting essay. I plan to work again next spring and summer at Trout Lake. Doing some quantitative sampling for densities and fecundity patterns could be interesting. Care to join me for part of the venture?

Nice review of the papers by Johnson et al. (2009) and Solomon et al (in press). By the way, in last summer’s experiments with a former student, I also found very little effect of Bellamya on Physa growth rates in the laboratory (Clark and Havel, unpublished data).

See also the paper of Pattinson et al. (2003) on invasive Daphnia. We discuss the same empty niche hypothesis as important for tropical D. lumholtzi invading reservoirs of the south-central US.

I don’t agree that Bellamya are that different in dominant feeding ecology from native gastropods. After all, Bellamya are well known to clean surfaces quite thoroughly, and are for sale by breeders on the internet for cleaning ornamental ponds. Perhaps more important is whether or not resources are indeed limiting. (Although I now see that you consider this later in your essay.)

Regarding your statement about Bellamya being a "model organism." I agree! Lots of ways to study general ecology principles. [e.g., see papers by Havel and Shurin (2004) and Havel et al. (2005)]

Your assertion that we are "without a single estimate of population size, even static, ever taken anytime, anywhere" is an exaggeration, of course. See Solomon et al. (2009): quantitative sampling (see methods par. 4) plus population density estimates (results par. 5). But, I agree that population and fecundity estimates would be useful for better understanding these study systems and the potential of exotic viviparid snails for population growth and expansion.

But regarding your suggestion that viviparids might be easy to sample, "sitting on clean sand at the bottom of bathtub reservoirs," lakes can be spatially very complex (macrophytes, rocks, sand, logs, leaf litter, flocculent organics). I found quantitative sampling to be a real challenge; but then I’m new to the benthos. (I could definitely use some help with these techniques.)

Additional references
Havel, J.E., and J.B. Shurin. 2004. Mechanisms, effects, and scales of dispersal in freshwater zooplankton: a synthesis. Limnology and Oceanography 49: 1229-1238. Havel, J.E., C. E. Lee, and J. Vander Zanden. 2005. Do reservoirs facilitate invasions into landscapes? BioScience 55: 518-525. Pattinson, K.R., J.E. Havel, and R.G. Rhodes. 2003. Invasibility of a reservoir to exotic Daphnia lumholtzi: Experimental assessment of diet selection and life history responses to Cyanobacteria. Freshwater Biology 48: 233-246.

(2) From David Campbell amblema@bama.ua.edu

Regarding Smith's (2000) preference for the generic nomen "Bellamya," unfortunately, he's led you astray. The type of Bellamya is from West Africa, and no East Asian species belongs in it (even if you put them in the same genus, there are older names both from Africa and from Asia). See... Mita E. Sengupta, Thomas K. Kristensen, Henry Madsen, Aslak Jørgensen. 2009. Molecular phylogenetic investigations of the Viviparidae (Gastropoda: Caenogastropoda) in the lakes of the Rift Valley area of Africa. Molecular Phylogenetics and Evolution 52:797–805 ...for the molecular data, though they don't deal with the nomenclatural implications, except for incorrectly suggesting that Neothauma should be included in Bellamya- Neothauma is the older name. It's still possible that some other name applies besides Cipangpaludina, but to determine that requires actually checking the type species of the nominal Asian genera.

(3) From Jeremy Tiemann jtiemann@inhs.uiuc.edu

Have you seen this paper yet? Bury, J.A. B.E. Sietman, and B.N. Karns. 2007. Distribution of the non-native viviparid snails, Bellamya chinensis and Viviparus georgianus, in Minnesota and the first record of Bellamya japonica from Wisconsin. Journal of Freshwater Ecology 22(4):697-703.

(4) From Bob Prezant prezantr@mail.montclair.edu

Rob, I agree...a "model organism" is just what we have in Bellamya. Can't remember if I sent this article to you. Hope you're warmer than we are here in NJ. Prezant, R. S., E. J. Chapman and A. McDougall (2006) In utero predator-induced responses in the viviparid snail Bellamya chinensis. Canadian Journal of Zoology 84: 600-608.

Mobile Basin IV: Goniobasis WTFs

Editor's Note.  This essay was subsequently published as: Dillon, R.T., Jr. (2019c) Mobile Basin III: Goniobasis clues.  Pp. 35-39 in The Freshwater Gastropods of North America Volume 3, Essays on the Prosobranchs.  FWGNA Press, Charleston.

Georgia is just Florida, one state north and 65 million years back. During the Cretaceous Period, most of the land mass that constitutes the present Mobile Basin of Alabama would have been obscured by a shallow sea and the occasional shadow of a passing mosasaur. The exception would have been a peninsula in what is today North Georgia (1).

Atlanta sits in the middle of that Cretaceous peninsula, General Sherman notwithstanding (2). The low hills to its east drain through the Ocmulgee/Oconee/Altamaha to the Atlantic. The Chattahoochee River runs through the middle of the city, under the I-285 beltway and southwest to the Gulf. To its immediate north lie tributaries of the Alabama/Coosa, draining into the Mobile Basin. And just a bit further north, the waters of the Tennessee River flow into the Mississippi (below, 3).

An appreciation of the complex drainage patterns of north Georgia will be important for an understanding of the hypotheses I am preparing to advance in this essay. If you are planning an earnest attempt to follow me, you will need to hold in your mind that the Coosa River is formed at the Georgia/Alabama line by the junction of two major tributaries, the (more northern) Conasauga/ Coosawattee/ Oostanaula and the (more southern) Etowah (4). And I do apologize for the drainage taxonomy. Subsequent to the departure of the mosasaurs, but prior to the arrival of Sherman, this part of the world was infested with dozens of Indian tribes, vying among one another in the unpronouncability of their names. After extinguishing each tribe, the European settlers named a local river in its honor, apparently careless of how, or even whether, any of these rivers might ultimately interconnect.

In any case, the diversity of the Goniobasis fauna of the Alabama/Coosa river system might aptly be described as "legendary." Goodrich (1936) recognized 24 species in the main river itself, and subsequently (1941) added about 11 species from "small streams." His final (1944) tally for the entire fauna of the Coosa River system listed, from rivers of all size, 29 species of Goniobasis, many with subspecies (5).

As patient and perceptive readers of this series of essays may have by now gathered, I myself have relatively little field experience anywhere in the Mobile Basin. What insight I have gathered regarding the pleurocerid fauna of the Oostanaula side of the Coosa has developed as a consequence of my work in east Tennessee on Goniobasis clavaeformis / Pleurocera unciale, as featured in last month’s (6) “Mobile Basin III.” When first I crossed the low hills that separate the Hiwassee system of the Tennessee River from the Mobile Basin in North Georgia, and peeked tentatively into the famously diverse waters of the Oostanaula subdrainage, I was shocked by the sight that met my eyes. WTF?!

This was the same pleurocerid fauna I had just spent the previous week sampling in Tennessee. In Cohulla Creek, one of the main tributaries of the Conasauga/Oostanaula east of Dalton, I recognized three old friends: Goniobasis simplex, G. troostiana (or "arachnoidea"), and G. clavaeformis – the same species widespread from southwest Virginia down the width of east Tennessee. The only difference was that clavaeformis was now called vestita, arachnoidea was now called striatula, and simplex was now called, well, I don't know (7). And the allozyme data I have subsequently collected seem to show that I was correct.

But it had happened before. My first “WTF moment” in the upper Mobile Basin actually occurred in the mid-1990s, kneeling beside the Etowah River. On that occasion I had been sampling west from the Atlantic drainages of central Georgia, crossed the broken Piedmont north of Atlanta, and found essentially the same G. catenaria I’d I had spent most of my professional career chasing through southern Virginia and the Carolinas, now re-named “Goniobasis caelatura” in the Etowah. And the DNA sequence data I have subsequently gathered with the help of my colleague John Robinson again seem to show that this impression was correct (8).

So we’ve now reached the point of a hypothesis – not just for this essay, but for all IV essays in this series. The endemicity of the Mobile Basin pleurocerid fauna has historically been much overstated. As the Cretaceous seas receded, the pleurocerid faunas that colonized the Mobile Basin were a mixture of the Atlantic (older) elements and the Tennessee (younger) elements, both previously inhabiting a peninsula in north Georgia. These faunas can still be seen today in the two major tributaries of the Coosa – the southern Etowah and the northern Oostanaula.

But don’t misunderstand me. There are bona fide endemic species of pleurocerid gastropods in the Mobile Basin. Dykes Creek is a lovely little stream running directly into the main Etowah River very near its junction with the Oostanaula. It is inhabited by (at least) three species: a G. clavaeformis-type from the Tennessee side (A), a chunky G. catenaria from the Atlantic side (B), and a species I'm going to call "WTF3" (C). Allozyme data show WTF3 to be genetically similar to G. catenaria, but reproductively isolated from it. My best guess is that Goodrich would have identified WTF3 as the subspecies Goniobasis caelatura sternsiana (Call 1886). But if so, that's the second of his caelatura "subspecies" that needs to be raised back up to the full species level (9). I am quite sure, in any case, that WTF3 is endemic to the Mobile Basin. And perhaps very rare.

So to summarize. In late June the US Fish and Wildlife service proposed endangered status for two Mobile Basin pleurocerids species, "Leptoxis foremani" and "Pleurocera foremani" (Essay I, 24Aug 09 - see note 10). The former nominal species is likely a local population of L. picta, which is not protected in any way (Essay II, 15Sept - see note 11). The latter nominal species is likely a local ecophenotypic variant of the most widespread pleurocerid in the American southeast (Essay III, 12Oct - see note 6). Meanwhile genuinely endemic and probably rare species go entirely unrecognized by anybody.

Science and public policy are two entirely different things. What I have been demonstrating over this four part series is science - the construction of testable hypotheses about the natural world. This process, this vocabulary, this way of looking at the world, is entirely different from the process that brought the US Fish & Wildlife Service to propose its endangered species regulations in the 29Jun09 Federal Register. These two ways of looking at the world are not compatible, nor are they incompatible. FWS biologists play baseball, I play the banjo. Neither is better, neither is worse.

I am not suggesting that the FWS drop "Leptoxis foremani" and "Pleurocera foremani" like a pair of old girlfriends and drive Dad's Chrysler up to Dykes Creek with flowers and bonbons to court G. stearnsiana, or whatever TF it is. Everything I've offered in this essay is a hypothesis (12), and may change tomorrow. What I am suggesting is that if it is the genuine Will of the People that public resources be expended on science (13), all government agencies involved (regardless of mission) must support what has heretofore been marginalized as "basic research," such as that which produced the hypotheses I have advanced above, which is, after all, the only real Science there is. In other words - send me money, and leave me TF alone.

I'm waiting,
Rob

Notes

(1) The best treatment of this subject I've been able to find on the web is at NOAA, interestingly: Beach Nourishment, A Guide for Local Government Officials

(2) Literally.

(3) I've stolen this map from the "Southeast Watershed Assistance Network."

(4) And here's the map of the Mobile Basin drainage system that I stole for Essay I in this series. You might want to open it in a new window.

(5) Goodrich, C. (1936) Goniobasis of the Coosa River, Alabama. Misc. Publ. Mus. Zool. Univ. Mich., 31, 1-60. Goodrich, C. (1941) Pleuroceridae of the small streams of the Alabama River system. Occas. Pprs. Mus. Zool. Univ. Mich., 427, 1-10. Goodrich, C. (1944) Pleuroceridae of the Coosa River basin. Nautilus, 58, 40-48.

(6) "Mobile Basin III: Pleurocera Puzzles." Post of October '09.

(7) This is actually one of the biggest mysteries in my mind regarding the Goniobasis of the Alabama/Coosa. What did Goodrich (and everybody else who has ever sloshed through these rivers) call plain old, ordinary, vanilla, dirt-common Goniobasis simplex? I can't match it to a synonym on anybody's list, over 150 years of surveys. Has it been missed?

(8) "The Snails the Dinosaurs Saw." Post of March '09.

(9) In the mid-1990s I also recognized Goniobasis georgiana in the Etowah, another older-Appalachian species ranging through the upper tributaries of the Hiwassee in the North Carolina mountains. Goodrich lowered this nomen to subspecific rank as "G. caelatura georgiana," but its co-occurrence in the Etowah with what (I suppose) he would have identified as G. caelatura caelatura, absent any evidence of hybridization, suggests strongly that G. georgiana is a distinct species.

(10) "Mobile Basin I: Two pleurocerids proposed for listing." Post of August '09.

(11) "Mobile Basin II: Leptoxis lessons." Post of September '09.

(12) Thompson (2000, Walkerana 11:1-54) has a different hypothesis. In the words of my favorite Alabamian, "That's all I've got to say about that."

(13) And I'm not sure it is!