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Thick-leaf Whitlow-grass - Draba crassa
State Rank Reason (see State Rank above)
Scattered across southwest Montana where it is known from alpine slopes in several mountain ranges. Overall abundance and distribution is still poorly known, though it is likely to be more common than collections indicate.
- Details on Status Ranking and Review
Population Size
Score2 - Small: Generally 2,000-10,000 individuals.
CommentEstimated as population levels from specimen collections are largely unknown.
Range Extent
Score1 - Peripheral, Disjunct or Sporadic Distribution in MT: Widespread species that is peripheral, disjunct or sporadically distributed within MT such that it occurs in <5% of the state (<7,500 sq. miles or the combined area of Beaverhead and Ravalli Counties) or is restricted to 4-5 sub-basins.
Area of Occupancy
Score1 - Moderate: Generally occurring in 11-25 Subwatersheds (6th Code HUC’s).
Environmental Specificity
Score1-2 - Moderate to High.
Trends
Score0-1 - Stable to Minor Declines:
CommentTrends unknown, though populations are likely stable or experiencing only minor declines.
Threats
Score0-1 - Low to Medium.
Intrinsic Vulnerability
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
Score
6 to 9 total points scored out of a possible 19.
General Description
Perennial from a simple or branched caudex clothed in old leaf bases. Stems simple, 4–12 cm. Basal leaves petiolate, oblanceolate, 2–5 cm long, entire. Stem leaves several, lanceolate, sessile. Vestiture of simple and forked hairs on the stem and sparse cilia on leaf margins. Petals yellow, 3–5 mm long. Fruit ascending, 5–9 × 3–5 mm, glabrous, often twisted; style 0.3–1 mm long; lower pedicels 2–8 mm long (
Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).
Species Range
Montana Range
Range Descriptions
Native
Range Comments
Regional endemic of south-central Montana, western Wyoming, northeastern Utah, and Colorado.
Observations in Montana Natural Heritage Program Database
Number of Observations: 21
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
Relative Density
Recency
(Observations spanning multiple months or years are excluded from time charts)
Habitat
Rocky areas in the alpine particularly on cool, shady sites.
Ecological Systems Associated with this Species
- Commonly Associated with these Ecological Systems
Alpine Systems
Stewardship Responsibility
Threats or Limiting Factors
STATE THREAT SCORE REASON
Reported threats to Montana’s populations of Thick-leaf Whitlow-grass include a population expected to decline by at least one-third where invasive weeds have strong negative impacts (MTNHP Threat Assessment 2021).
References
- Literature Cited AboveLegend:
View Online Publication- Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
MTNHP Threat Assessment. 2021. State Threat Score Assignment and Assessment of Reported Threats from 2006 to 2021 for State-listed Vascular Plants. Botany Program, Montana Natural Heritage Program, Helena, Montana.
- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?- Aho, Ken Andrew. 2006. Alpine and Cliff Ecosystems in the North-Central Rocky Mountains. Ph.D. Dissertation. Bozeman, Montana: Montana State University. 343 p.
- Lesica, P., M.T. Lavin, and P.F. Stickney. 2022. Manual of Montana Vascular Plants, Second Edition. Fort Worth, TX: BRIT Press. viii + 779 p.
- Rollins, R. C. 1993. The Cruciferae of Continental North America: systematics of the mustard family from the Arctic to Panama. Stanford University Press, Stanford, California. 976 pp.
- Web Search Engines for Articles on "Thick-leaf Whitlow-grass"
