Editor’s
Note – This essay was subsequently published as: Dillon, R.T., Jr. (2019c) Fred Thompson, Steve Chambers, and the pleurocerids of Florida. Pp 117 - 126 in The Freshwater Gastropods of North America Volume 3, Essays on the
Prosobranchs. FWGNA Press, Charleston.
Word has reached us of the death of Dr. Fred G. Thompson,
who passed away December 27, 2016 at his home in Ocala [1]. Dr. Thompson was Curator of Malacology at the
Florida Museum of Natural History in Gainesville for 40 years. He was 82.
Dr. Thompson’s body of published work must run into the
hundreds of titles – focusing primarily on the North American Hydrobiidae, but
extending to include the Pleuroceridae and a broad range of terrestrial
gastropod taxa as well, especially of Mexico and Latin America. I understand that his complete necrology will
soon be published in The Tentacle.
I had no personal relationship with the late Dr. Thompson. I did attend his talks at the AMU (later the
American Malacological Society) over a period of some thirty years, although I
don’t recall his attending any of mine. He did not respond to my letters or emails. During my visit to the Florida Museum in July of 2006 he did not emerge
from his office.
We did, of course, have many mutual colleagues. The American community of freshwater gastropod
workers is not a large one. All I know
about the personality and character of Dr. Thompson I have gathered from
friends. Good friends, like Steve
Chambers.
Steve Chambers was an important influence on my young
career. He first met Dr Thompson on a
field trip as a graduate student at the University of Florida in 1976, and
became interested in the genetic relationships among Florida pleurocerid
populations known at that time as Goniobasis, now Pleurocera. Steve’s major adviser, Dr. Thomas Emmel, ran
a big laboratory specializing in the promising new technique of allozyme
electrophoresis. Steve thought that the estimation
of genetic divergence among populations of pleurocerid snails as a function of
gene frequencies at multiple allozyme-encoding loci might elucidate
evolutionary principles of great generality and importance [2].
 |
| The Clench & Turner model, as figured by Chambers [7] |
The pleurocerid fauna of Florida is no less enigmatic than
that of most other regions of the American southeast. Goodrich [3] recognized three
species: catenaria (2 subspecies), clenchi and curvicostata, with boykiniana (3
subspecies) in nearby South Georgia.
Clench & Turner [4] took a big swing at this system, substituting
floridensis for catenaria cancellata, raising catenaria vanhyningiana to the
full species level, bringing one of the boykiniana subspecies down into Florida
(albanyensis) and raising it to the full species level as well. They also described two new species (athearni
and dickinsoni) which, together with clenchi and curvicostata yielded seven
species of Goniobasis in Florida.
It was the seven-species Clench & Turner model that Fred
Thompson preferred for the Pleuroceridae of Florida, and the seven-species
model is what Steve Chambers brought into his study design. His (1977) dissertation [5] was an impressive
effort to replicate the extremely influential Drosophila research that F. J.
Ayala [6] had published in 1974. Steve
showed that, just as in Drosophila, populations of Goniobasis at increasing
degrees of taxonomic divergence demonstrated increasing levels of genetic
divergence at allozyme loci. The paper
based on his dissertation research was published in 1980 [7].
Perhaps unsurprisingly, however, Steve’s genetic data did
not jive especially well with the Clench & Turner seven-species model. Allozyme divergence suggested that vanhyningiana
and clenchi be synonymized under floridensis and that albanyensis, athearni and
the REF population (more about which anon) “are in the range of conspecifics,”
although Chambers called for further study on that question. Note that by the time he had published his
dissertation in 1980 he had already synonymized clenchi (marked “F” in the
figure above) under floridensis.
Meanwhile, on a small farm in Kansas, a boy was growing up
[8]. Well, actually, he entered the
graduate program at the University of Pennsylvania in the fall of 1977, on a
scientific journey remarkably similar to that of Steve Chambers, just a couple steps
behind. My adviser was also running a big
lab specializing in the promising new technique of allozyme electrophoresis,
and I too was interested in the genetic relationships among populations of
Goniobasis, mine in the southern Appalachians.
And it turned out that my adviser, Dr. George Davis, was also the Editor of
the journal to which Steve Chambers sent his first two papers, the 1980 work
based on his dissertation and an earlier one on that “REF” population I
mentioned above.
Steve had discovered his REF population quite by
accident. He had gone to sample Ichetucknee
Springs (the source of North Florida’s Ichetucknee River) expecting to find a
typical population of Goniobasis floridensis, and that’s what he thought he
had, until he got back to the laboratory.
But his gels showed two reproductively isolated populations, one of
which matched floridensis genetically and the other of which was much more
similar to his sample populations of Goniobasis athearni and G.
albanyensis. He published “An
electrophoretically detected sibling species of Goniobasis floridensis” in
Malacologia in 1978 [9].
Both Steve’s 1978 and 1980 papers were highly influential in
my budding career. I struck up a
correspondence with him and he was happy to share techniques, recipes, and
tips. Imagine my surprise (and dismay)
when my adviser showed me a manuscript he had received attacking Steve
Chamber’s work gratuitously and viciously.
Fred Thompson had submitted a Letter to the Editor for
publication in Malacologia. The journal
very rarely published letters in those days.
In fact, no letters whatsoever had been published in the previous ten
years. But Dr. Thompson was livid about
research that had taken place at his own home institution, research that very
carefully and thoroughly documented a model of evolutionary relationships among
the Florida Goniobasis he did not share.
That letter was ultimately published in 1982, along with
Steve’s reply [10], over the protestations of a farm boy from Kansas [8]. It included such whoppers as “Because the
Ichetucknee population of athearni is distantly related genetically to floridensis,
they cannot be sibling species.” But the
amount of genetic divergence has nothing to do with sibling species. Ernst Mayr coined that term in 1963, and he
defined it as “morphologically similar or identical populations which are
reproductively isolated,” and genetic divergence does not enter into it [11]. In fact, whether the observed amount of genetic
divergence might correlate with the taxonomic divergence suggested by
systematic biologists was the very hypothesis that Steve was trying to test.
Well, by 1982 Steve had been gone from Gainesville for five
years. He told me later that he had been
a finalist for the opening at the University of Michigan Museum of Zoology left
vacant when Henry van der Schalie retired, but that Dr. Thompson had written an
unsolicited letter to his colleagues in Ann Arbor, scuttling Steve’s chances
for that job.
But Steve was able to land a job with the FWS Office of
Endangered Species in Washington, which turned out to be a plum. From Washington he was able to publish two
high-visibility works on chromosomal evolution in gastropods [12]. He also became interested in the land snail
fauna of the Galapagos, describing two new species of bulimulids in 1986 [13]. And with Christine Schonewald-Cox and other
colleagues he edited a very influential book on the budding discipline of
conservation genetics [14].
Meanwhile up north, the farm boy from Kansas [8] accepted an
AAAS congressional fellowship and moved to Washington for the 1981-82 academic
year, still right on the heels of his buddy Steve. And we struck up a personal friendship that
year which I wish had lasted longer. Toward
the end of my brief sojourn in Washington Steve remarked to me, and I’m
paraphrasing here, “In the entire wide community of systematic biology,
malacologists have the reputation of being the most petty and venal.” He was broadening his professional horizons, trying
to shift away.
And meanwhile down south, Dr. Thompson published the first
(1984) edition of his “Freshwater Snails of Florida” [15]. Perhaps unsurprisingly he clung to the Clench
& Turner seven-species model, citing the work of Chambers only once, superficially:
“Recent studies on isoenzymes show that, in Elimia, shell characters are
conservative indicators of genetic divergence (Chambers 1980, Dillon &
Davis 1980).” Regarding Dr. Thompson’s
choice of genus, see note [16] below.
 |
| From Chambers [17] |
After ten years in Washington, Steve was transferred to the
regional office in Albuquerque, where he became involved with federal efforts
to protect endangered elements of the charismatic megafauna such as the Red
Wolf. But he had one more snail paper in
the pipeline, his 1990 masterpiece “The genus Elimia in Florida and adjoining
drainage basins” [17]. Here Steve combined
his modern understanding of allozyme, chromosomal, and morphological divergence
in an enigmatic and misunderstood freshwater gastropod fauna together with a scholar’s
appreciation for the old literature and the old museum collections into a
symphony of Malacological virtuosity. He
convincingly demonstrated that there are four species of Goniobasis in Florida
and South Georgia – boykiniana (including athearni, albanyensis, and REF),
curvicostata, dickinsoni, and floridensis (including vanhyningiana and clenchi),
and the matter would seem to be settled.
But way back on page 261 of Chambers’ 1990 work we read:
“R. T. Dillon has sent me shells of Elimia catenaria Say from South Carolina and suggested that my E. boykiniana may be a synonym of E. catenaria. Although there is considerable merit in this suggestion, I decline to combine these Georgia and South Carolina populations with E. boykiniana at this time because they occur in major drainages for which genetic data are not available.”
Yes, after single years in Washington and at Rutgers, that
farm boy from Kansas [8] had arrived in Charleston, SC, and begun work to tie his
1982 dissertation research in VA/NC together with the remarkable body of
knowledge Steve Chambers had developed in FL/Ga. Could direct conflict with Dr. Fred Thompson be
avoided? Tune in next time.
Notes
[1] Fred Gilbert Thompson (November 13, 1934 – December 27,
2016). The Shell-O-Gram 58(1): 4-5.
[2] I did too, once.
When I was young.
[3] Goodrich, C. (1942) The Pleuroceridae of the Atlantic
Coastal Plain. Occas. Papers Mus. Zool.
Univ. Mich. 456:1 – 6.
[4] Clench, W. J. & R. D. Turner (1956) Freshwater
mollusks of Alabama, Georgia and Florida from the Escambia to the Suwannee
River. Bull. Florida State Museum 1:1 –
239.
[5] Chambers, S. M. (1977) Genetic divergence during
speciation in freshwater snails of the genus Goniobasis. Ph.D. dissertation, University of Florida, Gainesville.
59 pp.
[6] Ayala, F. J., M. L. Tracey, D. Hedgecock & R. C.
Richmond (1974) Genetic differentiation during the speciation process in
Drosophila. Evolution 28: 576-592.
[7] Chambers, S. M. (1980) Genetic divergence between
populations of Goniobasis (Pleuroceridae) occupying different drainage
systems. Malacologia 20: 63 – 81.
[8] Virginia, actually.
And he wasn’t born on a farm, and he never grew up, if you ask his
wife. For more, see…
- The Clean Water Act at 40 [7Jan13]
[10] Thompson, F. G. (1982) On sibling species and genetic
diversity in Florida Goniobasis.
Malacologia 23: 81 – 82.
Chambers, S. M. (1982) Sibling species and genetic diversity in Florida
Goniobasis: A reply. Malacologia 23: 83
– 86.
[11] Mayr, E. (1963) Animal Species and Evolution. Belknap Press, 797 pp. The definition of sibling species is found on
page 34.
[12] Chambers, S. M. (1982) Chromosomal evidence for
parallel evolution of shell sculpture pattern in Goniobasis. Evolution 36: 113 – 120.
Chambers, S. M. (1987) Rates of evolutionary
change in chromosome numbers in snails and vertebrates. Evolution 41: 166 – 175.
[13] Chambers, S. M. (1986) Two new bulimulid land snail
species from Isla Santa Cruz, Galapagos Islands. Veliger 28: 287 – 293.
[14] C.
Schonewald-Cox, S. Chambers, B. MacBryde, and L. Thomas (1983) Genetics and
Conservation: A Reference for Managing Wild Animal and Plant Populations. Benjamin Cummings, Menlo Park. 722 pp.
[15] Thompson, F.G., 1984. The freshwater snails of Florida:
A manual for identification. University of Florida Press, Gainesville, FL.
1-94.
[16] I suppose I should also mention that, separately but
essentially simultaneously, J. B. Burch was working on his North American
Freshwater Snails. The Burch &
Tottenham “Species List, Ranges and Illustrations” was published in 1980, with
the full EPA Manual following in 1982 and the stand-alone separate work
republished in 1989. This work proposed
a hybrid between the Goodrich and Clench & Turner classifications of the
Florida and South Georgia pleurocerid fauna, which did not evolve through its
extended publication history: athearni, clenchi, curvicostata, dickinsoni, induta,
and boykiniana with three subspecies.
The recognition of a separate floridensis, while keeping vanhyningiana as
a subspecies of catenaria, yielded a list of ten species and subspecies for the
region, which Burch renamed to “Elimia.”
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