Dr. Rob Dillon, Coordinator

Tuesday, September 14, 2010

Valvata utahensis and Hypothesis #2 (of 3)

Editor’s Note – This essay was subsequently published as: Dillon, R.T., Jr. (2019d) Valvata utahensis and Hypothesis #2 (of 3).  Pp 159 - 163 in The Freshwater Gastropods of North America Volume 4, Essays on Ecology and Biogeography.  FWGNA Press, Charleston.

Late last month, after many years of research, consultation, and study (1), the US Fish & Wildlife Service announced a finding that Valvata utahensis no longer warrants protection under the federal endangered species act. Quoting directly from the 25Aug10 press release (2), “The decision was made based on new scientific information that demonstrates the snail is more widely distributed and occurs in more habitat types than was known at the time the species was listed.”

Valvata utahensis was one of five freshwater gastropods from southern Idaho to enter the federal list on December 14, 1992. (Image at left from the USDA Rocky Mt. Res. Station). At the time, it was believed to occur “in a few springs and mainstem Snake River sites in the Hagerman Valley and at a few sites below American Falls Dam” in “deep pools adjacent to rapids or in perennial flowing waters associated with large spring complexes” (3). But subsequent status surveys have documented a range extending down 255 miles of the Snake River and across much greater variety of habitat types (4). In fact, V. utahensis seems to be found more abundantly in the impoundments behind the reservoirs than in the free-flowing river itself.

In many respects this episode has been quite similar to that involving the Snake River population of Pyrgulopsis robusta, which entered the US Endangered Species list on the same date as V. utahensis, preceding its removal by three years. Originally listed as “Pyrgulopsis idahoensis,” the Idaho Springsnail was believed to occur “at a few sites from the headwaters of C. J. Strike Reservoir at river mile 518 upstream to approximately river mile 553” (3). But several years of directed surveys found the Pyrgulopsis population actually extending over 80 river miles at an average density of 130/m2, making it one of the largest freshwater snail populations ever documented. And broader systematic research showed that the Snake River Pyrgulopsis was not endemic, but rather ranged across portions three other western states, under several older aliases (5).

Our understanding of the Snake River Pyrgulopsis progressed through a complete three-hypothesis evolution, from (#1) narrow endemic to (#2) regional endemic to (#3) non-endemic, as information accumulated. It appears that progress in Valvata research will be attenuated at Hypothesis #2, which is something of a shame. R. E. Call originally described utahensis as a variant of the much more widely-distributed Valvata sincera (6), and the shell characters on the basis of which Walker elevated utahensis to the specific level (7) are notoriously variable. But with the species delisted on the basis of Hypothesis #2, I fear that the interest of funding agencies in the more evolutionarily-interesting Hypothesis #3 will inevitably wane.

Meanwhile, our understanding of the “Snake River Physa” skipped from the hypothesis of narrow endemicity directly to non-endemic, without ringing the doorbell of Hypothesis #2 at all. After entering the list on 14Dec92 as “Physa natricina,” research on these enigmatic populations suffered an extended period of neglect, due both to the difficulty that field workers have encountered distinguishing it from commonplace Physa gyrina, and to the assumption that no Physa of any interest could easily be sampled from the shallows. So in December of 2007 the Snake River Physa hopped directly from narrowly endemic in deep water and strong currents from “Grandview (RM 492) upstream through the Hagerman Reach (RM 573)” to synonymy under the cosmopolitan Physa acuta, common in marginal and shallow habitats across six continents (8).

This was also a bit of a shame, from the standpoint of academic malacology. Although not anybody’s favorite hypothesis, it is certainly possible that some physid bearing a type-C penial morphology, but not correctly identified as either P. natricina or as P. acuta, might inhabit rivers of the Pacific Northwest. Judging from secondary sources, there seem to be at least two names that might apply to physids of the acuta type in the Snake/Columbia River system regionally, Physa concolor Haldeman 1843 (type locality = “Oregon”) and Physa columbiana Hemphill 1890 (type locality = Columbia R. at Astoria, OR). If we’d spent a few years exploring Hypothesis #2 for the Snake River physids, at least we’d have a bit more information about the ecology and evolution of the pulmonate fauna in an otherwise benighted part of the world.

It may yet happen. “Physa natricina” remains on the federal list of endangered species today, three years after its synonymization under P. acuta. And the “species profile” maintained by the FWS (9) contains an enigmatic reference to a population “as far downstream as Ontario, Oregon (RM 368).” Heaven knows what sort of elaborate processes would be required to effect the delisting of P. natricina (10), and whether it will prove to anybody’s political interest to undertake the task. I am quite certain, however, of one thing.

Over the last 20 years, literally thousands of man hours have been spent on surveys of the Snake River narrowly focused on particular target species, first Pyrgulopsis and more recently Valvata, and Taylorconcha serpenticola, which was also listed in 1992 and also spent many subsequent years in limbo (11). Hundreds of river miles have been traced and retraced and re-retraced, and nobody over all these years as far as I can determine has ever picked up a Physa. If some agency now finds it in the budget to fund yet another survey of the Snake River, this time for the physids, it would be helpful if the biologists involved were to sample the complete gastropod fauna, common and rare, for God’s sake, for a change. And share those results with the entire community.

Twenty years of wandering in the malacological wilderness of southern Idaho were touched off in 1992 by boneheaded spot-sampling (12). One might hope that we would, eventually, learn.


(1) I first featured the ongoing FWS “Comprehensive Status Review” of V. utahensis back in 2007:
More Snake River Gastropods Studied for Delisting (14June07)

(2) U.S. Fish and Wildlife Service finds Utah (Desert) Valvata Snail No Longer Needs Protection [PDF]

(3) Endangered and threatened wildlife and plants; Determination of endangered or threatened status for five aquatic snails in south central Idaho. Federal Register 57(240): 59244-57. (December 14, 1992) [PDF]

(4) Endangered and threatened wildlife and plants; Removal of the Utah (Desert) Valvata snail from the federal list of endangered and threatened wildlife. Federal Register 75(164): 52272-82. (August 25, 2010) [PDF]

(5) I posted four essays on the Snake River Pyrgulopsis controversy as it unfolded:
Idaho Springsnail Showdown (28Apr05)
Idaho Springsnail Panel Report (23Dec05)
When Pigs Fly in Idaho (30Jan06)
FWS Finding on the Idaho Springsnail (4Oct06)

(6) Call, R. E. (1884) On the Quaternary and recent Mollusca of the Great Basin, with descriptions of new forms. U.S. Geol. Survey Bulletin 11: 1-64.

(7) Walker, B. (1902) A revision of the carinate valvatas of the United States. Nautilus 15; 121-125.

(8) See my 2008 review of the “Snake River Physa” controversy in:
Red flags, water resources, and Physa natricina (14Mar08)

(9) See the main FWS page for the Snake River Physa [html]

(10) Actually, there’s a flowchart outlining the process in a document entitled “Delisting a Species” available from the Idaho FWS website. [PDF]

(11) The FWS announced a five year review of T. serpenticola (the “Bliss Rapids Snail”) in July 2004, but ultimately decided to preserve its threatened status:
Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition to Remove the Bliss Rapids Snail (Taylorconcha serpenticola) From the List of Endangered and Threatened Wildlife. Federal Register 74(178): 47536-45. (Sept. 16, 2009) [html]

(12) I’m being charitable here. There is some real possibility that the interests spearheading the 1992 listing process were not innocent naïfs, but cynically manipulating the endangered species act for politics and profit. The essay of [14Mar08] referenced in note (8) above was written in one of my less-charitable moods.