Painted Milkvetch - Astragalus ceramicus var. apus
State Rank Reason (see State Rank above)
Astragalus ceramicus variety apus is known only from the upper Snake River Plains of southeast Idaho and adjacent Montana, where it is restricted to the Centennial Valley of Beaverhead County. The disruption of natural disturbance regimes, including fire, ungulate grazing and pocket gopher activity, can lead to dune stabilization, reducing the extent of blowout areas with early successional vegetation, upon which this species depends. Portions of its habitat lie on private or public lands without sensitive species management policies in place.
- Details on Status Ranking and Review
Score1-2 - Small to Moderate. Population size is imprecisely known but is believed to be >2,000 individuals and <100,000 individuals.
CommentAvailable data on population levels are limited. Additional information needed.
Score3 - Local Endemic or Very Small Montana Range: Generally restricted to an area <10,000 sq. miles (equivalent to the combined area of Phillips and Valley Counties) or <6 Sub-basins (4th code watersheds) Range-wide OR limited to one Sub-basin in Montana
CommentVery small Montana range.
Area of Occupancy
Score3 - Very Low: Generally occurring in 3 or fewer Subwatersheds (6th Code HUC’s).
Score2 - High: Species is restricted to a highly specialized and limited habitat and is typically dependent upon unaltered, high-quality habitat (C Values of 8-10).
ScoreNA - Rank factor not assessed.
CommentTrend data are lacking, though there is no indication that the species' has experienced significant declines in Montana.
Score1-2 - Medium to High.
Score1 - Moderate Vulnerability: Specific biological attributes, unusual life history characteristics or limited reproductive potential makes the species susceptible to extirpation from stochastic events or other adverse impacts to its habitat and slow to recover.
Raw Conservation Status Score
11 to 13 total points scored out of a possible 16 (Rarity factors and threats only).
PLANTS: Perennial from rhizome-like caudex-branches (Barneby 1964). The root-crown is deeply buried but can become exposed by shifting sand of mobile dunes (Barneby 1964). Plants are densely strigose (Lesica et al. 2012). Stems solitary, lax to ascending, 10–25 cm (Lesica et al. 2012).
LEAVES: 1–12 cm long. Mostly pinnate with 1-7 leaflets; the terminal leaflet is longest and confluent with the rachis (Lesica et al. 2012). Petioles are slender (Barneby 1964). Stipules are lanceolate, 2–6 mm long, and often united basally.
INFLORESCENCE: Racemes of 2-10(25) white to light purple flowers. Racemes with spreading to ascending flowers grow among the leaves (Lesica et al. 2012).
In Montana we have two varieties: filifolius and apus (refer to Diagnostic Characteristics and Range Comments).
Flowering occurs from late June into July.
Astragalus ceramicus is unique in being diffusely cryptophytic (bears its buds below the soil), with confluent terminal leaflets, and an inflated pod that does not lose its red mottling (Barneby 1964). Its pods (fruits) are balloon-shaped, large, and red-mottled.
Variety apus has pods that are sessile to the stem and is endemic to Beaverhead County and adjacent Idaho (Lesica et al. 2012). Pods are 2-4 cm long and about 1.5-2.4 cm in diameter (Barneby 1964). Lateral leaflets are wanting or nearly so (Barneby 1964).
Variety filifolius has pods that have a stipe of 1-3 mm length and grows in the counties of eastern Montana, adjacent North and South Dakota, and other regions of the Great Plains (McGregor 1986, Flora of the Great Plains). Pods are (2)3-5 cm long and 1.4-2.6 cm in diameter (Barneby 1964). Some lower leaves may have 1-2(3) pairs of lateral leaflets (Barneby 1964).
Variety apus is endemic to Beaverhead County and adjacent southeast Idaho (Lesica et al. 2012). It is a regional endemic.
Variety filifolius grows in the counties of eastern Montana, adjacent North and South Dakota, and other regions of the Great Plains (Barneby 1964). It is rare in the Great Plains except in the sandhill region of Nebraska where it is common (McGregor 1986, Flora of the Great Plains).
Observations in Montana Natural Heritage Program Database
Number of Observations:
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
(Observations spanning multiple months or years are excluded from time charts)
Long distances between occurrences is thought to reduce opportunities for pollen exchange and has led to the perpetuation of small regional differences that consist of many minor races (Barneby 1964). Three varieties have been recognized since at least 1964: ceramicus, apus, and filifolius of which the latter two occur in Montana and are depicted in their own Plant Field Guide accounts.
The species is associated with early successional habitats in sandhills (Schassberger 1988). It is found in sandy, well-drained blowout areas and sandy flats or draws of old sand dunes at elevations of 6650-6700 feet, on moderately steep (20-30%), south- and west-facing slopes. Much of the vegetative cover consists of Artemisia tripartita, Phacelia hastata, Agropyron dasystachyum, Stipa comata and Tetradymia canescens.
Ecological Systems Associated with this Species
Painted milkvetch occurs in the sand dune region of the Centennial Valley where there is light to moderate grazing pressure (Culver 1993). It requires the open sand of early successional areas, and suitable habitat may be reduced when plant succession leads to later stages in which vegetation covers areas of formerly open sand (Lesica and Cooper 1998). Historically, the diversity of sandhills plant communities was maintained by a fire cycle of 20-30 years. The activity of pocket gophers (Thomomys talpoides) also appears to be an important force in initiating blowouts and maintaining early seral vegetation (Lesica and Cooper 1998).
In 1987, the populations in the Centennial Sandhills were reported to be thriving; however in 1993, Culver observed only a few small populations, suggesting that the number of above-ground stems may vary from year to year. A follow-up to this observation is greatly needed.
The removal of natural disturbance regimes, including fire, ungulate grazing and pocket gopher activity, leads to dune stabilization and reduces the extent of early seral blowout vegetation areas upon which this species depends. Painted milkvetch would benefit from restoration of the fire regime and moderate grazing, at least in years following burns. Severe destabilization of the dunes, e.g., from off-road vehicle use, could also threaten its habitat.
Threats or Limiting Factors
Studies have shown that Painted milkvetch occurs in early successional habitats that are maintained by grazing or fire. Threats would include any process or action that hinders or prevents grazing or fire. Plants occur in habitats where the potential for off-road recreational vehicles use is real; however, actual use has not been documented at any known occurrence. Invasive plants are a potential threat to its habitat though current assessments on the condition of occupied habitats have not been made.
- Literature Cited AboveLegend: View Online Publication
- Barneby, R.C. 1964. Atlas of North American Astragalus. 2 Vols. New York Botanical Garden, Bronx, New York. 1188 pp.
- Lesica, P., M. T. Lavin, and P. F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
- McGregor, R.L., coordinator, and T.M. Barkley, R.E. Brooks, and E.K. Schofield, eds.: Great Plains Flora Association. 1986. Flora of the Great Plains. Lawrence, KS: Univ. Press Kansas. 1392 pp.
- Additional ReferencesLegend: View Online Publication
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- Culver, D.R. 1993. Sensitive plant species inventory in the Centennial Valley, Beaverhead County, Montana. Unpublished report to the Butte District, Bureau of Land Management. Montana Natural Heritage Program, Helena, 42 pp. plus appendices.
- Lesica, P. & S. V. Cooper. 1998. Succession and disturbance in sandhills vegetation: constructing models for managing biological diversity. Conservation Biology 13:293-302.
- Schassberger, L.A. 1987. The ecology of Astragalus ceramicus var. APUS in relation to succession in the Centennial Sandhills of southwestern Montana. [Progress report to The Nature Conservancy].
- Schassberger, L.A. 1988. Effects of grazing on the habitat of Astragalus ceramicus var. Apus in the sandhills of the Centennial Valley, Montana. M.A. thesis. University of Montana, Missoula, Montana.