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!
Notes
[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.
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