Plants and Rocks: columbines and granite

Laramie columbine on Laramie granite.  Upside-down US dime is 1.9 cm (0.75 in) across.

 In the summer of 1887, 28-year-old Aven Nelson left Iowa for Laramie City in Wyoming Territory, having been hired as Professor of English at the new University of Wyoming.  When all six faculty members had arrived, University President J. W. Hoyt realized there was a problem -- he had mistakenly hired two English professors.  While Nelson had a Bachelor of Arts and Didactics degree from the State Normal School in Kirksville, Missouri, the other guy -- W. I. Smith -- had a Master’s Degree in English from Dartmouth College, and got the job.

Old Main, the first building at the University of Wyoming, was completed September 1, 1887, just in time for classes. (This photo was taken in 1908).

Biography of Aven Nelson (Williams 1984).

Hoyt interviewed Nelson to see what other subjects he might be qualified to teach.  Nelson explained his love of natural history, his excursions in search of wildflowers, and the six lectures on plants he had attended at the Normal School in Iowa -- this was enough to justify appointment as Professor of Biology at the new university.  From that strange beginning, Aven Nelson went on to become the preeminent botanist of the Rocky Mountain region for many years.  He started the Rocky Mountain Herbarium, now recognized as one of the major collections in the United States, and in his 55-year career described numerous new plant species.  Perhaps his most important contribution was as teacher, as many of his students went on to become eminent botanists themselves.

In 1894 Nelson began a systematic survey of Wyoming plants.  He spent two months in the field, traveling on horseback with a hired guide and outfitter.  They went by way of Douglas, Casper, Lander, Jackson Hole, Green River, South Pass, and Bates Hole, camping out most of the time.  Nelson reported that they had a tent along but rarely used it, the weather being fine for sleeping under the stars.  By the end of the field season he had collected 1,200 specimens, which he explained would have been impossible without the help of his diligent student assistant.

Nelson's collecting areas, 1894 and 1895 (Nelson 1896; click to view).

The next field season consisted of several shorter expeditions, including one to the rugged northern Laramie Range in early August.  One objective was to climb Laramie Peak, which at 10,276 feet elevation (3132 m) stands significantly higher than the rest of the range.  The party approached the peak from the east, following the Cottonwood Creek drainage to “the foot of Laramie Peak”.  On August 4, Nelson found a small columbine growing “in a canon where it occupied the dry crevices in abrupt cliffs”.  They went on to climb Laramie Peak the next day, and returned home with 117 collections; the total for the season was 670.

Laramie Peak viewed from south.  DT Horning photo.

In 1896 Nelson published the First report on the Flora of Wyoming, including a list of the 1176 known plants of the state (today’s flora is estimated at 2800).  He made it clear that much more work remained to be done.  Nelson also described four new species and eleven new varieties, a major achievement for a botanist still early in his career.  The columbine from Cottonwood Canyon was one of the new species, formally named Aquilegia laramiensis -- Laramie columbine.

Rugged country in the northern Laramie Range.  Cottonwood Canyon, type
locality for the Laramie columbine, is behind the ridge in the foreground.
Laramie Peak is out of view to the left (west).  DT Horning photo.

Like its much better known relative the Colorado columbine, the Laramie columbine has flowers with spurred petals.  But the flowers are much smaller -- the spurs of the petals are only 10 mm long while those of the Colorado columbine can be up to 50 mm long.  The entire plant is less than 20 cm tall.  The flowers are white to pale blue.

Laramie columbine.
Illustration by Isobel Nichols.

Colorado columbine, courtesy US Forest Service.

Nelson made several more collections of the Laramie columbine in 1900 and 1901, including one from ca. 60 miles south of Laramie Peak, a major range extension.  No additional locations were documented for seventy years.  Starting in the 1970s, new populations were occasionally reported; by 2002 the species was known from 13 sites.

Surveys of the Laramie columbine were done in 2003, 2004 and 2009, funded by the US Forest Service and Bureau of Land Management.  The species is now known from 51 sites, all in the northern Laramie Range, i.e. the Laramie columbine is endemic (restricted) to the northern part of the range (Marriott and Horning 2010).  This is a case of narrow endemism as the species grows in a very limited area -- all but one of the known sites are clustered in a narrow zone approximately 55 km (32 mi) in length.

Distribution map for Laramie columbine (green dots; from Marriott and Pokorny 2006).

The Laramie columbine grows on suitable microsites on igneous and metamorphic rocks -- typically in small pockets of coarse soil in crevices, on small ledges or at the base of outcrops, and almost always where there is little or no other vegetation.  Populations are small; the largest ones contain perhaps 100 individuals.  So how rare is this plant?  While we know that it is a narrow endemic, we still don’t know how abundant it is within its range, even after all that work.  Why?  Because this is the kind of country in which the Laramie columbine grows!

There is a wealth of potential habitat in this photo, and much of it is time-consuming, difficult or impossible for a field botanist to access (photo by DT Horning).

Most known populations of Laramie columbine grow on the Archean “Laramie granite” (Condie 1969, Johnson and Hills 1976) which forms the maze in the photo above.  A few scattered populations have been found to the south in the central metamorphic complex -- a zone of Archean rocks metamorphosed during Proterozoic events (Patel et al. 1999).  Further south where the Proterozoic Sherman granite dominates, the columbine apparently is absent; none have been found in spite of easy access and frequent collecting.

Precambrian rocks of the Laramie Range, click to view.
(from Marriott and Pokorny 2006, modified from Johnson and Hills 1976).

Laramie columbines at base of granite outcrop.
DT Horning photo.

What is it about the “Laramie granite” that makes it such good habitat for the Laramie columbine?  It seems to provide the right kinds of microsites:  shaded, flat to gently sloping, and with some soil development but not enough to support other vegetation.  This last habitat feature is shared by many of the narrowly-endemic rare plants of Wyoming -- they grow where other plants don’t.

And what is it about the “Laramie granite” that requires putting the name in quotation marks?  Alas, it is not an accepted name -- not recognized in the USGS GEOLEX database nor by recent workers (e.g. Patel et al. 1999).  It was applied by Condie (1969) in a study of the petrology and geochemistry of the granite and adjacent metamorphic rocks.  He described the mass of granite as the “Laramie batholith”, and suggested the best explanation for its genesis was “fractional crystallization of an intermediate or mafic magma derived by the partial melting of the lower crust or upper mantle.”

Condie’s 1969 paper elicited a quick and forceful response from Smithson and Hodge (also 1969) who argued that his conclusions were unsupportable, especially in the southern part of the study area where they themselves were working.  Their main objection was insufficient time in the field:  “A central question relates to how many days were spent in the field on the study. ... The area is exceptionally large (4000 km2) and complex.”  Laramie columbine surveyors would agree!

Johnson and Hill (1976) sampled the northern part of the “Laramie granite” more intensively, arriving at the same conclusions as Condie but wisely making it clear that their findings should not be extrapolated beyond their study area.  Patel et al. (1999) avoided controversy altogether by calling the Archean granite simply “granite” of the “Laramie Peak block”.

Recent work in the Laramie Range has focused on the more exciting Archean craton margin -- the central metamorphic complex and Proterozoic hard rocks to the south.  And so the granite to the north remains officially nameless.  Those of us studying the Laramie columbine continue to call its substrate the “Laramie granite” as it serves the purpose of communication.  And besides ... it's only fitting that Laramie columbine should grow on Laramie granite.

Aven Nelson in the field, from UW archives.

Literature Cited

Condie, K.C. 1969. Petrology and geochemistry of the Laramie batholith and related metamorphic rocks of Precambrian age, eastern Wyoming. Geological Society of America Bulletin 80:57-82.

Johnson, R.C. and F.A. Hills. 1976. Precambrian geochronology and geology of the Boxelder Canyon area, northern Laramie Range, Wyoming. Geological Society of America Bulletin 87:809-817.

Marriott, H. and M.L. Pokorny.  2006.  Aquilegia laramiensis A. Nelson (Laramie columbine): a technical conservation assessment. USDA Forest Service, Rocky Mountain Region. Available:  www.fs.fed.us/r2/projects/scp/assessments/aquilegialaramiensis.pdf [accessed December 2011].

Marriott, H. and D. Horning.  2010.  Results of field survey and status report update for Laramie columbine (Aquilegia laramiensis). Unpublished report prepared for the Wyoming Natural Diversity Database, University of Wyoming, and the Bureau of Land Management, Casper Field Office.  Available:  www.uwyo.edu/wyndd/_files/docs/reports/wynddreports/u10mar01wyus.pdf [accessed December 2011].

Nelson, A.  1896.  First report on the flora of Wyoming. WY Agr. Exp. Sta. Bull. 28:78-79.

Patel, S.C., B.R. Frost, K.R. Chamberlain and G.L. Snyder.  1999.  Proterozoic metamorphism and uplift history of the north-central Laramie Mountains, Wyoming, USA.  J. Metam. Geol. 17:243–258.

Smithson, S.B., D.S. Hodge.  1969.  Petrology and geochemistry of the Laramie batholith and related metamorphic rocks of precambrian age, eastern Wyoming: discussion.  Geol. Soc. of Am. Bull. 80:2383-2384.

Williams, R. L.  1984.  Aven Nelson of Wyoming.  Boulder, CO:  Colorado Associated University Press.