Oxytropis besseyi var. obnapiformis
Author: (C.L. Porter) Welsh


Bessey locoweed


Fabaceae (Pea Family)

Close up of Oxytropis besseyi var. obnapiformis by Delia Malone
Click image to enlarge.

Taxonomic Comments

Ranks and Status

Global rank: G5T2
State rank: S2
Federal protection status: None
State protection status: None

[+] Description and Phenology

Oxytropis besseyi var. obnapiformis: artist unknown. Source: 1979 USFWS Illustrated Guide to Proposed, Threatened, and Endangered Species in CO.
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General description: Oxytropis besseyi var. obnapiformis is a densely hairy perennial herb with a stout taproot and stems up to 20 cm tall. Leaves are all basal, 10-20 cm long, usually equaling or surpassing the flowering stems, and have 9-15 leaflets. Hairs are basally attached to the leaves. Flower stems are 2-19 cm tall, each with 3-20 (rarely up to 29) pink to purple pea flowers. The calyx is less than 5 mm wide. Pods are papery, sessile or nearly so, hairy, and strongly inflated (Barneby 1989).

<i>Oxytropis besseyi </i>var. <i>obnapiformis </i>is a densely hairy perennial herb with a stout taproot and stems up to 20 cm tall. Leaves are all basal, 10-20 cm long, usually equaling or surpassing the flowering stems, and have 9-15 leaflets.  Hairs are basally attached to the leaves.  Flower stems are 2-19 cm tall, each with 3-20 (rarely up to 29) pink to purple pea flowers.  The calyx is less than 5 mm wide. Pods are papery, sessile or nearly so, hairy, and strongly inflated (Barneby 1989).  Pods are ovoid or subglobose (Ackerfield 2012).

Look Alikes: Oxytropis lambertii calyx is not inflated, and the pods are elongated (lance- to linear-ellipsoid) and protrude from the calyx (Ackerfield 2012, Weber and Wittmann 2012). Oxytropis lambertii also has hairs attached at points near the middle rather than at the bases as in O. besseyi var. obnapiformis (Wyoming Natural Diversity Database 2012).

Phenology: This species flowers May through July (Cronquist 1989, Colorado Natural Heritage Program 2012).

[+] Habitat

Habitat of Oxytropis besseyi var. obnapiformis by Delia Malone
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This species is associated with pinyon-juniper and sagebrush communities, often on barrens in either fine-textured or sandy substrates (Welsh 1993). Found on hilltops, bluffs, and breaks along rivers of foothill gulches, sandy or shaley talus, less often on tuffaceous knolls or sand dunes (Cronquist 1989).

Elevation Range: 5,358 - 8,432 feet (1,633 - 2,570 meters)

[+] Distribution

Distribution of Oxytropis besseyi var. obnapiformis in Colorado according to mapped land ownership/management boundaries (CNHP 2012, COMaP v9 ).
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Distribution of Oxytropis besseyi var. obnapiformis in Colorado
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Colorado endemic: No
Global range: Regional endemic of northeastern Utah, southwestern Wyoming, and northwestern Colorado.

State range: Known from Moffat and Rio Blanco counties in Colorado. Estimated range in Colorado is 4333 square kilometers (1673 square miles), calculated in GIS by the Colorado Natural Heritage Program in 2008 by drawing a minimum convex polygon around the known occurrences.

[+] Threats and Management Issues

Summary results of an analysis of the status of Oxytropis besseyi var. obnapiformis based on several ranking factors. This species was concluded to be “Weakly Conserved”. From Rondeau et al. 2011.
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The primary threat is considered to be oil and gas development (Rondeau et al. 2011). It is not known if all of the occurrences are or are not threatened by these activities. Occurs on BLM land with no special protection status. Other potential threats include excessive grazing. One occurrence is threatened due to its proximity to campgrounds (Colorado Natural Heritage Program 2012).

[+] References

    • Ackerfield, J. 2012. The Flora of Colorado. Colorado State University Herbarium. 433 pp.
    • Barneby, R.C. 1989. Fabales. In A. Cronquist, A.H. Holmgren, N.H. Holmgren, J.L. Reveal, and P.K. Holmgren (eds.). Intermountain flora: Vascular plants of the Intermountain West, U.S.A. Vol. 3, Part B. New York Botanical Garden, Bronx. 279 pp.
    • Beardsley, M. and D. A. Steingraeber. 2013. Population dynamics, rarity and risk of extirpation for populations of Mimulus gemmiparus (budding monkeyflower) on National Forests of Colorado. A research report submitted to the USFS Forest Service. Arapaho and Roosevelt National Forets and Pawnee National Grassland. pp 17. Accessed online on May 11 at: http://www.r5.fs.fed.us/wildflowers/Rare_Plants/profiles/Critically_Imperiled/mimulus_gemmiparus/ documents/USFS_MimulusStatusReport2013.pdf
    • Colorado Natural Heritage Program. 2009. The Sixth Annual Colorado Rare Plant Symposium: G2G3 Plants of North and Central Colorado. Symposium Minutes. Available on-line http://www.cnhp.colostate.edu/teams/botany.asp#symposia.
    • Colorado Natural Heritage Program. 2012. Biodiversity Tracking and Conservation System. Colorado State University, Fort Collins, CO.
    • Colorado Rare Plant Guide. 2013. Plant profile for Oxytropis besseyi var. obnapiformis. Accessed online on Nov. 17, 2014 at: http://www.cnhp.colostate.edu/download/projects/rareplants/guide.asp?id=20295
    • Cronquist A. 1989. Intermountain Flora Vascular Plants of the Intermountain West, USA. Vol. 3, Part B. New York Botanical Garden, Bronx, NY.
    • Fertig, W. 2001. Oxytropis besseyi var. obnapiformis. State Species Abstract. Wyoming Natural Diversity Database. Accessed online on Nov. 19, 2014 at: http://www.uwyo.edu/wyndd/_files/docs/reports/speciesabstracts/oxytropis_besseyi_obnapiformis.pdf
    • Harrington, H. D. 1954. Manual of the Plants of Colorado. Sage Books, Denver, CO. 666 pp.
    • Isley, D. 1983. New combinations and two new varieties in Astragalus, Orophaca, and Oxytropis (Leguminosae). Systematic Botany, Vol. 8, No. 4, pages 420-426.
    • Kartesz, J.T. 1999. A synonymized checklist and atlas with biological attributes for the vascular flora of the United States, Canada, and Greenland. First edition. In: Kartesz, J.T., and C.A. Meacham. Synthesis of the North American Flora, Version 1.0. North Carolina Botanical Garden, Chapel Hill, N.C.
    • Lavender, A.E., M.M. Fink, S.E. Linn, D.M. Theobald. 2011. Colorado Ownership, Management, and Protection v9 Database. Colorado Natural Heritage Program and Geospatial Centroid, Colorado State University, Fort Collins, CO. (30 September).
    • Neely, B., S. Panjabi, E. Lane, P. Lewis, C. Dawson, A. Kratz, B. Kurzel, T. Hogan, J. Handwerk, S. Krishnan, J. Neale, and N. Ripley. 2009. Colorado Rare Plant Conservation Strategy, Developed by the Colorado Rare Plant conservation Initiative. The Nature Conservancy, Boulder, Colorado, 117 pp.
    • Porter, C.L. 1947. A new species of Oxytropis from the Central Rocky Mountains. Madrono, vol. 9: pp. 133-135.
    • Rondeau, R., K. Decker, J. Handwerk, J. Siemers, L. Grunau, and C. Pague. 2011. The state of Colorado's biodiversity 2011. Prepared for The Nature Conservancy. Colorado Natural Heritage Program, Colorado State University, Fort Collins, Colorado.
    • USDA, NRCS. 2013. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.
    • Utah Native Plant Society. 2003-2014. Utah rare plant guide. A.J. Frates editor/coordinator. Salt Lake City, UT. Utah Native Plant Society. Online. Available: http://www.utahrareplants.org (accessed 2014).
    • Weber, W. A. and R. C. Wittmann. 2012. Colorado Flora, Western Slope, A Field Guide to the Vascular Plants, Fourth Edition. Boulder, Colorado. 532 pp.
    • Weber, W.A., and R.C. Wittmann. 1996a. Colorado flora: Eastern slope. Revised edition. Univ. Press of Colorado, Niwot, Colorado. 524 pp.
    • Welsh, S.L, N.D. Atwood, S. Goodrich, and L.C. Higgins. 1993. A Utah Flora, second edition, revised. Brigham Young University, Provo, UT.
    • Wyoming Natural Diverisity Database. 2012. Plant Species of Concern. Accessed at: http://www.uwyo.edu/wyndd/species-of-concern/plants/vascular-plants.html

Last Updated

2013-02-26