Dr. Rob Dillon, Coordinator

Tuesday, February 5, 2013

The Mystery of the SRALP: A Bidding...

Editor’s Note – This essay was subsequently published as: Dillon, R.T., Jr. (2019d) The Mystery of the SRALP: A Bidding...  Pp 165 - 171 in The Freshwater Gastropods of North America Volume 4, Essays on Ecology and Biogeography.  FWGNA Press, Charleston.

The invitation arrived by email on 19Aug2010.  Mr Ryan Newman of the US Bureau of Reclamation (USBR) was curious to know whether I might be available to join a working group convening in Boise to review a report by K. Gates & B. Kerans entitled, “Snake River Physa, Physa (Haitia) natricina, survey and study.”  And so began one of the greater malacological adventures of my life, professional or otherwise.

Faithful readers may remember my post of March 2008 regarding the federally-endangered Physa natricina [1].  Described by Dwight Taylor (1988) in one move of an (ultimately successful) effort to thwart the impoundment of the last free-flowing section of the Snake River in southern Idaho, the species was for many years a phantom – no precise localities known, even the type specimens lost.  Its habitat seemed to be unique among physids, “on boulders in the deepest accessible portion of the Snake River near rapid margins” [2].  The adults were unusually small-bodied (shell length “5.4 – 6.9” mm), bearing an unusually wide aperture.  See note [3] for more about the photo below.

Taylor went to some length to distinguish his Physa natricina from Physa gyrina – the former having a one-part penial sheath (“type-c”) and the latter a two-part sheath (“type-b”).  But in late 2007 Rogers and Wethington [4] pointed out that Taylor’s anatomical description was not sufficient to distinguish P. natricina from the worldwide invasive P. acuta*, another type-c physid apparently common in the shallows throughout most of the Snake.  Since stunted size and an odd aperture might simply reflect ecophenotypic responses to life in a habitat to which physids are marginally suited at best, Rogers and Wethington synonymized Taylor’s nomen natricina under P. acuta.  One might think this would end the matter.

But a controversy every bit as political as that which prompted the 1992 listing of Physa natricina had been simmering for some years in the Snake River tailwaters below Minidoka Dam, 20 miles upstream (NE) of Burley.  There macrobenthic surveys conducted in the mid-1990s by biologists working for the Bureau of Reclamation had returned small, oddly-shaped physids identified by consultants in 2004 as Physa natricina.  This prompted the US Fish & Wildlife Service to issue a “Biological Opinion” in March of 2005 [5] affecting the USBR’s management [6] of Minidoka Dam.  So in August of 2005 the USBR commissioned a study [7], which by August of 2010 had yielded fruit.  And I was being invited to review the result.

The 87-page Gates & Kerans report attached to Mr. Newman’s bidding comprised three sections – a survey, a morphological study, and a DNA sequence study.  The survey section spun a ripping-good yarn of suction dredges and tethered scuba divers, ultimately triumphing in the recovery of a remarkable 274 small, oddly-shaped type-c physids from the roiling waters of the Snake River below Minidoka Dam.  The second section reported a conventional study of the shell and anatomy of six of these small snails, featuring a photo of a couple living individuals (“courtesy of John B. Burch”).  And the third section, contributed by collaborators at both Montana State and the University of Michigan, reported an average 19.7% mtDNA sequence divergence between approximately 30 of these little snails (combined over both labs) and a sample of Physa gyrina.

And here’s the headline.  Gates &  Kerans reported an eye-popping 17.1% average sequence divergence between their sample of small, oddly-shaped type-c physids and Physa acuta sequences retrieved from Genbank.

But alas.  Gates & Kerans seemed entirely ignorant of (or worse, dismissive of?) the Rogers and Wethington report of Physa acuta* in the Snake River.  And the nearest P. acuta sequence available for comparison in GenBank had been sampled 500 km NE of the Minidoka Dam, on the other side of the Rocky Mountains in Wyoming.  And Gates & Kerans had not (apparently) felt called to sample their own.

Granted, the Rogers and Wethington study was not published until after the 2007 field season, by which time two years of data were already in the can.  But it seemed to me that, as soon as the existence of P. acuta* in the Snake River became known, those populations became the only appropriate control for the study of P. natricina, not P. acuta sampled across the continental divide 500 km northeast, and certainly not P. gyrina. The relevant morphological comparison would be between the population of small, oddly-shaped type-c Physa at mid-river in the Snake and equally small P. acuta* sampled from its shallows.  Gates and Kerans needed DNA samples from Snake River acuta*; neither Snake River gyrina nor Wyoming P. acuta were germane.

At this point in our malacological adventure I find it convenient to introduce a new term, “Snake River acuta-like Physa,” or SRALP for short.  And request that my readership mentally replace all five instances of the binomen "Physa acuta” marked with asterisks above with “SRALP.”  And find it necessary to reverse the flow of my narrative once again, back to an essay I wrote in September, 2010 [8].

That particular essay was prompted by the de-listing of Valvata utahensis and Pyrgulopsis robusta, two of the other four freshwater gastropod species politically listed in 1992 to block the Snake River impoundment.  In that 2010 essay I made reference to what seemed like a logical progression of three hypotheses – narrow endemic, regional endemic, and nonendemic – and lamented how natural resource politics had for 20 years short-circuited the (otherwise orderly) examination of all three.  And toward the end of that essay I pointed out that, in the case of Physa natricina, nobody seems to have given any study to “Hypothesis #2 (of 3)” at all.

The Gates & Kerans report was on my desk at the time I wrote my 2010 essay, and the timing was not a coincidence.  Does the Gates & Kerans sample of 274 small type-c Physa come from a narrowly endemic species, restricted to “boulders in the deepest accessible portion of the Snake River,” best identified as Physa natricina?  Or perhaps those 274 snails are simply ecophenotypic variants of the nonendemic P. acuta, otherwise common in the Snake River backwaters and elsewhere throughout the world?  Or might the Snake River be home to a regional endemic – locally common and practically indistinguishable from acuta in the calm backwaters, but rare, stunted and misshapen in the rapids?  The names concolor (Haldeman 1843) and columbiana (Hemphill 1890) are already in the literature for this second (of the three) possibilities. 

The answer to these questions and more would rest in the SRALP.  What exactly is that population of type-c physids reported common in the Snake River by Rogers and Wethington?  And what might their relationship be to the 274 odd little physids heroically retrieved by Gates & Kerans?  Tune in next time, as we journey to southern Idaho, on a quest!


[1] Red flags, Water Resources, and Physa natricina [12Mar08]

[2]  The “deepest accessible portion” quote comes from Taylor’s (1982) “Status Report on Snake River Physa Snail” (USFWS, Portland).  Taylor’s formal description of 1988 did not include habitat notes of any sort, oddly.

[3] The shell labelled "natricina" was dead-collected in the "drift" on one of the rocky beaches below the Minidoka Dam on 19Sept10.  Its collector was John Keebaugh, who identified it and made a gift of it to me.  I myself had collected the P. gyrina from a seep near the Minidoka Dam spillway earlier that morning.  And I also collected the individual labelled "SRALP" (Snake River acuta-like Physa) later that same day from the Snake River at Owsley (RM 582).  More in our next installment.

[4] Rogers, D. C. & A. R. Wethington (2007)  Physa natricina Taylor 1988, junior synonym of Physa acuta Draparnaud, 1805 (Pulmonata: Physidae).  Zootaxa 1662: 45 – 51.

[5] USFWS (2005)  Biological Opinion for Bureau of Reclamation Operations and Maintenance in the Snake River Basin Above Brownlee Reservoir.  This and all the other documents regarding the 2004-05 Minidoka controversy (including the implementation plan for a Physa study) are available from the Bureau of Reclamation here: [USBR 2004 Biological Assessment].

[6]  All the 2005 fussing (that came to my ears, anyway) focused on the annual schedule of water release from the Minidoka Dam, the FWS pressing for something closer to natural flow.  It also turns out that the USBR had been studying the complete replacement of the Minidoka Dam spillway since at least 2000, although I didn’t hear about that element of the controversy until 2010.  Here is the USBR page with all the documents relating to the spillway replacement: [USBR Spillway Replacement].

[7] To be as complete and fair as possible.  My first visit to Minidoka Dam came in December of 2005 as a member of a “Snake River Physa Technical Team” convened by the Bureau of Reclamation to provide recommendations for their study (documents at Note 5 above).  At the time, there was real concern that even if any small, misshapen type-c physids might be recovered from the Minidoka tailwaters, nobody could positively confirm their identity as P. natricina.  And I had not heard another word about the project as of 12Mar08, hence the reference to “a day which never arrived” in my 2008 blog post. 

But (in fact) the Gates & Kerens study was already into its third year by the spring of 2008.  I was invited to a second meeting of the Snake River Physa Technical Team on 1May2008, although not offered any funding to get me there.  So I told Mr. Newman that “if I happen to be in Boise on May 1, I’ll drop by.”  I would nevertheless have been happy to read a written progress report, had Mr. Newman offered one in 2008, which he did not.  Thus the desirability of standards and controls in scientific investigation was not called to the attention of Gates & Kerans until the fall of 2010, by which time there seems to have been little opportunity for a remedy.

[8] Valvata utahensis and Hypothesis #2 (of 3)  [14Sept10]

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