Astragalus anisus - M.E. Jones
Gunnison's Milkvetch
Other Common Names: Gunnison milkvetch
Taxonomic Status: Accepted
Related ITIS Name(s): Astragalus anisus M.E. Jones (TSN 25417)
Unique Identifier: ELEMENT_GLOBAL.2.144739
Element Code: PDFAB0F0N0
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 anisus
Conservation Status
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NatureServe Status

Global Status: G2G3
Global Status Last Reviewed: 11Dec2015
Global Status Last Changed: 19May2008
Ranking Methodology Used: Ranked by calculator
Rounded Global Status: G2 - Imperiled
Reasons: Although Astragalus anisus is locally common and appears to have a stable population, the species entire global range is contained within the upper Gunnison Basin, in Gunnison and Saguache counties, Colorado. Threats are low to moderate. Only six occurrences are considered to be of good viability.  Best management practices have been developed to help off-set impacts from the species' primary threat, roads and road construction (Panjabi and Smith 2014).
Nation: United States
National Status: N2N3

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 (S2S3)

Other Statuses

NatureServe Global Conservation Status Factors

Range Extent Comments: The species entire global range is contained within the upper Gunnison Basin, in Gunnison and Saguache counties, Colorado. Estimated range is 1,962 square kilometers (757 square miles), calculated in GIS in 2008 by the Colorado Natural Heritage Program by drawing a minimum convex polygon around the known occurrences.

Area of Occupancy: 26-125 4-km2 grid cells
Area of Occupancy Comments: The total occupied habitat is about 1,241 acres. Occurrences without specific information on occupied habitat were considered to occupy 0.5 acre.  As of the 2014 rank assessment, the area of occupancy was calculated base on element occurrence data to be 57, 4 sq km grid cells.

Number of Occurrences: 21 - 80
Number of Occurrences Comments: There are 41 principal occurrences documented in the Colorado Natural Heritage Program database (2013). Four of the 41 occurrences have not been observed in over 20 years, and one is presumed extirpated (X?). The USFS Conservation Assessment documents 83 occurrences (Decker and Anderson 2004). It is likely that this discrepancy in the total number of occurrences is because some of the sites reported by Decker and Anderson are represented in the Heritage database as portions of other occurrences and not reported separately.

Population Size Comments: Total estimated sum of individuals from 10 of the 35 documented occurrences is 565. The remaining occurrences do not report the number of individuals. Described as locally abundant. Wasson 1998 counted a total of 4200 plants in 33 populations.

Number of Occurrences with Good Viability/Integrity: Few (4-12)
Viability/Integrity Comments: There are 6 occurrences with an A or B rank.

Overall Threat Impact: Medium
Overall Threat Impact Comments: The greatest threat to this species and its conservation is lack of awareness that it exists and it's narrow-endemic status. However, to increase awareness and protection Best Management Practices have been developed (Panjabi and Smith 2014).  Another primary threat at this time is considered to be road building (Decker and Anderson 2004, Rondeau et al. 2011). Other threats are from off-road vehicle use, non-motorized recreation, non-native species invasion, grazing, residential development, fire suppression, resource extraction, and global climate change. Climate change has shifted the blooming time for this species to more than a month earlier than it bloomed in the 1800s (Munson and Sher 2015).   A lack of systematic tracking of population trends and conditions and a lack of knowledge about the species' basic life cycle also contribute to the possibility that one or more of these factors will threaten its long-term persistence (Decker and Anderson 2004).

Short-term Trend: Relatively Stable (<=10% change)
Short-term Trend Comments: The numbers of plants in individual populations fluctuate dramatically between years, but there are no data to allow trends to be quantified (Decker and Anderson 2004). In the absence of data to the contrary, the population is believed to be stable (Decker and Anderson 2004).

Long-term Trend: Unknown

Other NatureServe Conservation Status Information

Distribution
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Global Range: The species entire global range is contained within the upper Gunnison Basin, in Gunnison and Saguache counties, Colorado. Estimated range is 1,962 square kilometers (757 square miles), calculated in GIS in 2008 by the Colorado Natural Heritage Program by drawing a minimum convex polygon around the known occurrences.

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

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
CO Gunnison (08051), Saguache (08109)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
14 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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Basic Description: Colorado endemic in Gunnison and Saguache counties. Racemes of 3 to 7 flowers, pink-purple, corolla 15-20 mm long. Ovoid strigose pods, 15 to 20 mm in length. Dwarf plants, 5 to 10 cm in height. Leaves with 9 to 15 leaflets, each 4 to 10 mm in length, tomentose, and silvery.
General Description: Astragalus anisus is a short, tufted perennial with basal leaves that arise from a very short stem above a woody taproot. The caudex, or stem base, often shows the thatched remains of old leaves. The leaves are pinnately compound, up to 7 cm long, with 11 to 15 leaflets. The entire plant appears silvery-gray due to the presence of numerous hairs of a characteristic dolabriform (ax or pick-shaped) shape. Flowers are borne on short racemes and are typically pink-purple in color. The pods (fruits) are short (1.3 to 1.8 cm in length) and almost round, though somewhat compressed from front to back, and of a fleshy texture with flat-lying hairs. Fruits are originally green in color, becoming brown with maturity. Each fruit contains 28 to 40 ovules. Seeds are smooth, black, and small (2.0 to 2.4 mm in length). The fruit is bilocular (has two chambers), often appears red or orange when inflated, and splits into two sections when dry (Decker and Anderson 2004).
Duration: PERENNIAL
Terrestrial Habitat(s): Shrubland/chaparral
Habitat Comments: Found within Sagebrush Shrubland (dominated by Artemisia tridentata ssp. tridentata, Artemisia tridentata ssp. vaseyana, Artemisia tridentata ssp. wyomingensis, or Artemisia cana) and Sagebrush Shrub Steppe (dominated by Artemisia nova or Artemisia arbuscula) ecological system types; primarily within the Dry Sagebrush Shrubland type. Usually found in fairly open sites where sagebrush shrubs do not form a closed canopy, but sometimes shelters under low sagebrush plants. Sites are characterized by the absence of trees, moderate shrub cover, moderate understory cover, and extensive bare ground. Found on flats on the floor of the Gunnison Basin and on hillsides. Usually on sandy clay to gravelly soils overlying granitic bedrock; parent materials include rhyolite, tuff, gneiss, and schist. Slopes range 0 - 34% (average 17.3%) and aspects are usually west-facing. Other associated species include Phlox hoodii, Bouteloua gracilis, Poa fendleriana, and Stipa pinetorum.  (Decker and Anderson 2004).
Economic Attributes
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Economically Important Genus: Y
Management Summary Not yet assessed
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Population/Occurrence Delineation
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Minimum Criteria for an Occurrence: Any naturally occurring population that is separated by a sufficient distance or barrier from a neighboring population. As a guideline, EOs are separated by either: 1 mile or more across unsuitable habitat or altered and unsuitable areas; or 2 miles or more across apparently suitable habitat not known to be occupied. Justification: The rationale for this large a separation distance across suitable but apparently unoccupied habitat is that it is likely additional research will find this habitat to be occupied. It can often be assumed that apparently unconnected populations will eventually be found to be more closely connected; these are best regarded as suboccurrences. No information on mobility of pollen and propagules is available on which to base the separation distance for this species.
Date: 27Sep2000
Author: Spackman, S., and D. Anderson.
Population/Occurrence Viability
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Excellent Viability: Size: 500 or more individuals (based on available EOR data). Condition: The occurrence has an excellent likelihood of long-term viability as evidenced by the presence of multiple age classes and evidence of flowering and fruiting, indicating that the reproductive mechanisms are intact. This occurrence should be in a high-quality site with less than 1% cover of exotic plant species and/or no significant anthropogenic disturbance. Landscape Context: The occurrence is surrounded by an area that is unfragmented and includes the ecological processes needed to sustain this species. This species may depend on the presence of a natural fire regime in the sagebrush shrubland matrix community in which it is found. Justification: There is sparse information on abundance for this species. The specification guidelines are based on EO specs for other rare species in this genus. Large populations in high quality sites are presumed to contain a high degree of genetic variability, have a low susceptibility to the effects of inbreeding depression, and to be relatively resilient. When more information is acquired, the EO specs should be reassessed.
Good Viability: Size: 100 or more individuals (based on available EOR data). Condition: The occurrence should have a good likelihood of long-term viability as evidenced by the presence of multiple age classes and evidence of flowering and fruiting, indicating that the reproductive mechanisms are intact. Anthropogenic disturbance within the occurrence is minimal. If exotic species are present, they comprise less than 10% of the total ground cover. Landscape Context: The surrounding landscape should contain the ecological processes needed to sustain the occurrence but may be fragmented and/or impacted by humans.
Fair Viability: Size: 20 to 200 individuals (based on available EOR data). Condition: The occurrence may be less productive than the above situations, but is still viable, with multiple age classes and evidence of flowering and fruiting, indicating that the reproductive mechanisms are intact. The occupied habitat is somewhat degraded (exotic plant species make up between 10-50% of the total ground cover and/or there is a moderate level of anthropogenic disturbance). Landscape Context: There may be significant human disturbance, but the ecological processes needed to sustain the species are still intact.
Poor Viability: Size: Less than 20 individuals (based on available EOR data). Condition: Little or no evidence of successful reproduction is observed (poor seedling recruitment, no flowering or fruiting observed, or poor age class distribution). Exotic plant species make up greater than 50% of the total ground cover, and/or there is a significant level of human disturbance. Landscape context: The surrounding area is fragmented with many ecological processes no longer intact. The occurrence has a low probability of long-term persistence due to inbreeding depression, natural stochastic events, and its intrinsic vulnerability to human impacts.
Justification: Justification: EOs not meeting "C"-rank criteria are likely to have a very high probability of inbreeding depression and extirpation due to natural stochastic processes and/or occur in degraded habitat with low long-term potential for survival.
Key for Ranking Species Element Occurrences Using the Generic Approach (2008).
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: 11Dec2015
NatureServe Conservation Status Factors Author: Fayette, K., rev. Neuhaus, K., J. Handwerk, and S. Spackman Panjabi (2006); rev. Smith, P. (2013), rev. L. Oliver (2015)
Element Ecology & Life History Author(s): rev. SSP (2013)

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. 2012. The Flora of Colorado. Colorado State University Herbarium. 433 pp.


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

  • Barneby, R.C. 1964. Atlas of North American Astragalus. 2 Vols. New York Botanical Garden, Bronx, New York. 1188 pp.

  • Decker, K. and D.G. Anderson. 2004. Astragalus anisus M.E. Jones (Gunnison milkvetch): a technical conservation assessment. USDA Forest Service, Rocky Mountain Region. Online. Available: http://www.fs.fed.us/r2/projects/scp/assessments/astragalusanisus.pdf (Accessed 2006).

  • Isely, D. 1998. Native and naturalized Leguminosae (Fabaceae) of the United States (exclusive of Alaska and Hawaii). Monte L. Bean Life Science Museum, Brigham Young University; MLBM Press, Provo, Utah. 1007 pp.

  • Jones, M.E. 1923. Revision of North-American Species of Astragalus. Salt Lake City, UT.

  • 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.

  • Munson, S. M. and A. A. Sher. 2015. Long-term shifts in the phenology of rare and endemic Rocky Mountain plants. American Journal of Botany 102: 1268-1276.

  • Neely, B., R. Rondeau, J. Sanderson, C. Pague, B. Kuhn, J. Siemers, L. Grunau, J. Robertson, P. McCarthy, J. Barsugli, T. Schulz, and C. Knapp. Editors. Gunnison Basin: Vulnerability Assessment for the Gunnison Climate Working Group by The Nature Conservancy, Colorado Natural Heritage Program, Western Water Assessment, University of Colorado, Boulder, and University of Alaska, Fairbanks. Project of the Southwest Climate Change Initiative.

  • 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.

  • Panjabi, S.S. and G. Smith, 2014. Recommended best management practices for Gunnison milkvetch (Astragalus anisus): practices developed to reduce the impacts of road maintenance activities to plants of concern. Colorado Natural Heritage Program, Colorado State University, Fort Collins, Colorado. Accessed online on: Dec 7, 2015 at https://www.codot.gov/programs/environmental/wildlife/guidelines/rare-plant-bmps/astragalus-anisus

  • 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.

  • 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. 

  • Rydberg, P.A. 1906. Flora of Colorado. Agricultural Experiment Station of the Colorado Agricultural College, Fort Collins.

  • Spackman, S., B. Jennings, J. Coles, C. Dawson, M. Minton, A. Kratz, and C. Spurrier. (Web authors: Johnson, C.S. and M. Barry). 1999. Colorado rare plant field guide. Prepared for Bureau of Land Management, U.S. Forest Service and U.S. Fish and Wildlife Service by Colorado Natural Heritage Program. Online. Available: http://www.cnhp.colostate.edu/rareplants/cover.html (Accessed 2006)

  • Spackman, S., B. Jennings, J. Coles, C. Dawson, M. Minton, A. Kratz, and C. Spurrier. 1997. Colorado rare plant field guide. Prepared for Bureau of Land Management, U.S. Forest Service and U.S. Fish and Wildlife Service by Colorado Natural Heritage Program.

  • The Colorado Native Plant Society. 1997. Rare Plants of Colorado, second edition. Falcon Press Publishing Co.,Inc. Helena, Montana. 105pp.

  • USDA, NRCS. 2013. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.

  • Wasson, A. 1998. Astragalus anisus in the Gunnison Basin: A Demographic Study.

  • Wasson, A. 1998. Astragalus anisus in the Gunnison Basin: A Demographic Study.

  • Welsh, S.L. 2007. North American Species of Astragalus Linnaeus (Leguminosae) A Taxonomic Revision. Brigham Young University, Provo, Utah. 932 pp.

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