Rocky Mountain Twinpod - Physaria saximontana var. dentata
State Rank Reason (see State Rank above)
State endemic known from several counties across central and southern Montana mountain ranges.
- Details on Status Ranking and Review
Score1 - Moderate: Generally 10,000-100,000 individuals.
CommentPopulation size likely >10,000 individuals though precise population data are lacking.
Score2 - Regional or State Endemic or Small Montana Range: Generally restricted to an area <100,000 sq. miles (equivalent to 2/3 the size of Montana or less) or Montana contributes 50% or more of the species’ range or populations OR limited to 2-3 Sub-basins in Montana.
Area of Occupancy
Score1 - Moderate: Generally occurring in 11-25 Subwatersheds (6th Code HUC’s).
Score1 - Moderate: Species is restricted to a specific habitat that is more widely distributed or to several restricted habitats and is typically dependent upon relatively unaltered, good-quality habitat (C Values of 5-7).
Score0-1 - Stable to Minor Declines:
CommentTrends are undocumented, though populations are likely stable or experiencing only minor declines as the species often occurs in remote, rocking habitats.
Score0-1 - Low to Medium.
Score0-1 - Low to Moderate Vulnerability.
Raw Conservation Status Score
5 to 8 total points scored out of a possible 19.
Stems ascending to prostrate, 3–10 cm from a simple caudex clothed in old leaf bases. Basal leaves 15–40 mm long; the blades orbicular to rhombic, deeply few-toothed or lyrate. Stem leaves oblanceolate to spatulate, entire. Vestiture of dense, stellate hairs with branched stellae. Petals 8–12 mm long. Fruit of 2 ovate lobes, inflated, 7–11 mm high, the apical sinus deep, the basal sinus absent; style 5–7 mm long; seeds 2 per locule; pedicels spreading, straight to curved, 5–10 mm long. Our plants are subspecies dentata
(Rollins) O'Kane (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX)
Flowering and fruiting in June and July with fruits maturing into August.
Only variety dentata occurs in Montana. Variety saximontana, which is only known from Wyoming, can be distinguished by its entire basal/rosette leaves and longer styles (3 or more times the length of the replum) vs. the toothed apical margins of the basal/rosette leaves of variety dentata and the shorter styles (1-2 times or less the length of the replum). Another species occurring in southwest Montana is P. didymocarpa, which differs in having deep sinuses at both the top and bottom of the fruit. The fruit of P. saximontana is notched with only a sinus at the top.
Montana endemic. Scattered across several counties in the central and western parts of the state.
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)
Typically found in limestone-derived talus, fellfields, and gravelly slopes at moderate to high elevations.
Ecological Systems Associated with this Species
- Additional ReferencesLegend: View Online Publication
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- Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
- Mincemoyer, S. 2005. Surveys of significant plant resources and related vegetation types for the Butte Office of the Bureau of Land Management. Montana Natural Heritage Program, Helena, MT. 11 pp + appendices.
- Rollins, R. C. 1984. Studies in the Cruciferae of western North America II. Contributions Gray Herbarium 214:1-18.
- 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.