Astragalus molybdenus - Barneby
Molybdenum Milkvetch
Other English Common Names: Leadville Milkvetch
Other Common Names: Leadville milkvetch
Taxonomic Status: Accepted
Related ITIS Name(s): Astragalus molybdenus Barneby (TSN 25590)
Unique Identifier: ELEMENT_GLOBAL.2.131837
Element Code: PDFAB0F5M0
Informal Taxonomy: Plants, Vascular - Flowering Plants - Pea Family
 
Kingdom Phylum Class Order Family Genus
Plantae Anthophyta Dicotyledoneae Fabales Fabaceae Astragalus
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Concept Reference
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Concept Reference: Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Concept Reference Code: B94KAR01HQUS
Name Used in Concept Reference: Astragalus molybdenus
Taxonomic Comments: Astragalus molybdenus, as treated here, follows the concept of Kartesz (1999), excluding plants in Montana (recognized as the separate species A. lackschewitzii), but including plants from Colorado and Wyoming (Wyoming plants have been distinguished as A. shultziorum) based on Kartesz's 1998 review draft and discussion with him on 14Dec98; however, Montana is shown in the distribution of A. molybdenus in the published Kartesz Synthesis (1999). Lavin and Marriott (1997) recognize three different species: plants in Montana are A. lackschewitzii, plants in Wyoming are A. shultziorum, and A. molybdenus is restricted to Colorado. Kartesz's 1994 treatment of A. molybdenus included Colorado, Montana, and Wyoming plants (as indicated in 1996 unpublished distribution data).
Conservation Status
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NatureServe Status

Global Status: G3
Global Status Last Reviewed: 05Jan1998
Global Status Last Changed: 05Jan1998
Rounded Global Status: G3 - Vulnerable
Reasons: Less than 20 occurrences in Colorado, 8 populations in Montana, and 19 occurrences in Wyoming. Threats moderate. If treated in the strict sense, this species would exclude the plants from Montana and Wyoming, which have been described as distinct from Astragalus molybdenus by Lavin and Marriott (1997), and it would be considered a Colorado endemic.
Nation: United States
National Status: N3

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Colorado (S2), Wyoming (SNR)

Other Statuses

NatureServe Global Conservation Status Factors

Range Extent Comments: Astragalus molybdenus in the broad sense occurs in Montana, Wyoming, and Colorado (USDA NRCS 2017). According to Lavin and Marriott (1997): A. molybdenus in the strict sense is endemic to a relatively small region in central Colorado in Gunnison, Park, Pitkin, and Summit Counties; A. shultziorum (included in A. molybdenus here) is endemic to Wyoming, from the Salt River and Wyoming Ranges in Lincoln County, the Gros Ventre Mountains in Sublette County, and the Teton Range in Teton County; and A. lackschewitzii (included in A. molybdenus here) is endemic to the Rocky Mountain front range in west-central Montana, Teton County.

Number of Occurrences: 21 - 80
Number of Occurrences Comments: 19 occurrences in 5 counties in Colorado. 8 populations in Sawtooth Range, Teton county, Montana (1990). 19 occurrences in Wyoming as Astragalus shultziorum (1996).

Population Size Comments: Based only on three occurrences which estimate population size of approximately 100 individuals.

Overall Threat Impact Comments: Mining and oil drilling may be a problem. Hiking and camping may also impact these populations. From Steve Olson (USFS Pike San Isabel) 2012: Threats to Astragalus molybdenus include unregulated recreation (off-road vehicles, hiking, snowmobiles), mining activities, interspecific competition, livestock grazing, and climate change (Ray 2001, Ladyman 2003, NatureServe 2011).

Other NatureServe Conservation Status Information

Distribution
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Global Range: Astragalus molybdenus in the broad sense occurs in Montana, Wyoming, and Colorado (USDA NRCS 2017). According to Lavin and Marriott (1997): A. molybdenus in the strict sense is endemic to a relatively small region in central Colorado in Gunnison, Park, Pitkin, and Summit Counties; A. shultziorum (included in A. molybdenus here) is endemic to Wyoming, from the Salt River and Wyoming Ranges in Lincoln County, the Gros Ventre Mountains in Sublette County, and the Teton Range in Teton County; and A. lackschewitzii (included in A. molybdenus here) is endemic to the Rocky Mountain front range in west-central Montana, Teton County.

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map

U.S. & Canada State/Province Distribution
United States CO, WY

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
CO Gunnison (08051), Hinsdale (08053), Lake (08065), Park (08093), Pitkin (08097), Summit (08117)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
10 South Platte Headwaters (10190001)+
11 Arkansas Headwaters (11020001)+
14 Blue (14010002)+, Roaring Fork (14010004)+, East-Taylor (14020001)+, Upper Gunnison (14020002)+, Tomichi (14020003)+*
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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General Description: Astragalus molybdenus is a perennial herb. It is a low-growing, loosely tufted, rhizomatous plant (Ladyman 2003). It is typically 2.5 to 7.6 cm (1 to 3 inches) tall. Leaves are pinnately compound with 9 to 25 (usually 13-19) silvery-gray, oval-oblong leaflets (Ladyman 2003, Ray 2001). Flowers are pale purplish or pinkish, and may have whitish stripes (Ladyman 2003, Ray 2001). There are conspicuous black hairs on the calyx tube. Plants have one or two clusters of two or three flowers each (Ray 2001). The legumes are 7 to 10 mm (0.25 to 0.4 inch) long, and are slightly in-curved (Ladyman 2003).

Diagnostic Characteristics: The genus ASTRAGALUS is very large, and many species that superficially resemble each other can occur in the same habitat. Both A. ALPINUS and A. BOURGOVII are small, low species that occur on limestone at high elevations in northwestern Montana. ASTRAGALUS ALPINUS has leaflets that are blunt at the tip and pods that are almost completely divided into two chambers. The pods of A. BOURGOVII are oval in cross-section, while those of A. MOLYBDENUS are more nearly triangular.
From Steve Olson (USFS Pike San Isabel) 2012: Diagnostic characters of Astragalus molybdenus include the black hairs on the calyx tube, and the appressed-ascending hairs on the stem of a small alpine Astragalus.

Reproduction Comments: From Steve Olson (USFS Pike San Isabel) 2012: Astragalus molybdenus often appears in colonies due to the presence of rhizomes and stolons.  Population sizes are extremely variable from isolated individuals to over a million stems (Ladyman 2003).  Flowers are pollinated by bumblebees and flies (Ladyman 2003).


From Steve Olson (USFS Pike San Isabel) 2012: Astragalus molybdenus often appears in colonies due to the presence of rhizomes and stolons. Population sizes are extremely variable from isolated individuals to over a million stems (Ladyman 2003).
From Steve Olson (USFS Pike San Isabel) 2012: Astragalus molybdenus often appears in colonies due to the presence of rhizomes and stolons.  Population sizes are extremely variable from isolated individuals to over a million stems (Ladyman 2003).  Flowers are pollinated by bumblebees and flies (Ladyman 2003).
 

Habitat Comments: A subalpine to alpine species which occurs in vegetative mats or on open scree. The habitat in which Astragalus molybdenus occurs varies across its range. In Colorado, Astragalus molybdenus inhabits strictly the alpine tundra, 3625 to 3960 m elevation. It is abundant on rocky soils where vegetation mats form 100% cover. Associated plant species often include Claytonia megarhiza, Kobresia sp., Oxyria digyna, and Silene acaulis. According to label data, the substrate of many of the sites is composed primarily of limestone, at least in part. In Wyoming, plants inhabit primarily the subalpine zone, rarely reaching the lowest limits of the alpine zone, 2680 to 3200 m. It is abundant on bare ground, often on scree slopes, and co-occurs with few other mat-forming plants. Co-occurring alpine species include Achillea millefolium, Aster alpigenus, Castilleja sulphurea, Salix glauca, and Sibbaldia procumbens. The substrate of all sites is composed primarily of limestone, and open soils are often very coarse and pebbly. In Montana, plants inhabit the subalpine to alpine zone, 2210 to 2475 m, and predominates in vegetative mats, often composed mostly of Dryas octopetala that can form up to 100% plant cover. It may also inhabit sites with less cover, even on bare ground, such as scree slopes. The substrate of all sites is composed primarily of limestone. (Habitat data summarized from Lavin and Marriott 1997)
 

Economic Attributes
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Economically Important Genus: Y
Management Summary Not yet assessed
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Population/Occurrence Delineation Not yet assessed
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Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 17May1996
NatureServe Conservation Status Factors Author: Fayette, K., rev. G. Thunhorst (12/97)
Element Ecology & Life History Edition Date: 01Oct1994
Element Ecology & Life History Author(s): JM

Botanical data developed by NatureServe and its network of natural heritage programs (see Local Programs), The North Carolina Botanical Garden, and other contributors and cooperators (see Sources).

References
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  • Ackerfield, J. 2015. Flora of Colorado. Brit Press, Botanical Research Institute of Texas, Fort Worth, TX. 818 pp.

  • Barneby, R. C. 1964. Atlas of North American Astragalus. Memoirs of New York Botanical Garden, vol. 13. New York Botanical Garden, Bronx, NY.

  • Colorado Natural Heritage Program and the Geospatial Centroid. 2017. The Colorado Ownership and Protection Map (COMaP). Colorado State University, Ft. Collins, CO.
     

  • Harrington, H. D. 1954. Manual of the Plants of Colorado. Sage Books, Denver, CO. 666 pp.

  • Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.

  • Kartesz, J.T. 1996. Species distribution data at state and province level for vascular plant taxa of the United States, Canada, and Greenland (accepted records), from unpublished data files at the North Carolina Botanical Garden, December, 1996.

  • Lavin, M. and H. Marriott. 1997. Astragalus molybdenus s.l. (Leguminosae): Higher taxonomic relationships and identity of constituent species. Systematic Botany 22(2):199-217.

  • Lavin, M., S. Mathews, C. Hughes, H. Marriott and S. Shelly. 1990. Intraspecific chloroplast DNA diversity is high in some wild species of Leguminosae. Amer. J. Bot. 77 (supplement):144 (abstract).

  • Ryke, N., D. Winters, L. McMartin and S. Vest. 1994. Threatened, Endangered and Sensitive Species of the Pike and San Isabel National Forests and Comanche and Cimarron National Grasslands. May 25, 1994.

  • Schassberger, L. A. and J. S. Shelly. 1990. Status review and taxonomic studies of Astragalus molybdenus, Lewis and Clark National Forest. Unpublished report. Montana Natural Heritage Program, Helena, MT. 45 pp.

  • USDA, Natural Resources Conservation Service, PLANTS Database [USDA PLANTS]. http://plants.usda.gov/. Accessed 2017.

  • Weber, W. A. and R. C. Wittmann. 2012. Colorado Flora, Eastern Slope, A Field Guide to the Vascular Plants, Fourth Edition. Boulder, Colorado. 555 pp.

  • 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.

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