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Porsild's Draba - Draba porsildii
State Rank Reason (see State Rank above)
Only known in Montana from a few collections on the Beartooth Plateau and the Madison Range. Current population levels and trends are unknown. However, its high-elevation habitat is relatively inaccessible, and there are no obvious threats. Additional sites are likely to be documented.
- Details on Status Ranking and Review
Score2-3 - Very Small to Small: Population size is imprecisely known but is believed to be <10,000 individuals.
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
Score3 - Very Low: Generally occurring in 3 or fewer Subwatersheds (6th Code HUC’s).
Score1-2 - Moderate to High.
Score0-1 - Stable to Minor Declines:
CommentTrends unknown, though populations are likely stable or experiencing only minor declines.
Score0-1 - Low to Medium.
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
8 to 12 total points scored out of a possible 19.
Porsild's Draba is a low perennial herb with few to many leafless stems that are 1-6 cm high and which arise from basal leaf rosettes that, in turn, arise from the ends of a simple or branched rootcrown. The lance-shaped leaves are 3-12 mm long, have entire margins, and are covered with branched hairs. The stalked flowers are borne at the tops of the stems in nearly flat-topped inflorescences. Each flower has 4 separate sepals, 4 separate, white petals, and 4 long and 2 short stamens. The style is ca. 0.2 mm long. The glabrous, narrowly elliptic capsules are 4-8 mm long and are borne on ascending stalks that are 1-2 mm long.
Flowering in July, fruiting in July-August.
There are many similar-appearing species of Draba in our area. A technical manual and hand lens or microscope are required for positive identification. Draba lonchocarpa, a more common white-flowered species, has capsules that are usually greater than 8 mm long.
YT south to CO. In MT known only from the Beartooth Range in Carbon County (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX)
Observations in Montana Natural Heritage Program Database
Number of Observations:
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Map Help and Descriptions
(Observations spanning multiple months or years are excluded from time charts)
Moist, gravelly open soil in the alpine zone.
Ecological Systems Associated with this Species
- Commonly Associated with these Ecological Systems
Threats or Limiting Factors
STATE THREAT SCORE REASON
Threat impact not assigned because threats are not known (MTNHP Threat Assessment 2021).
- 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.
- Additional ReferencesLegend: View Online Publication
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- Lesica, P. 1993. Vegetation and flora of the Line Creek Plateau area, Carbon County, Montana. Unpublished report to USDA Forest Service, Intermountain Research Station. Montana Natural Heritage Program, Helena, Montana. 30 pp.
- Mulligan, G.A. 1976. The genus Draba in Canada and Alaska: key and summary. Canadian Journal of Botany 54:1386-1393.
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