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Wyoming Tansymustard - Descurainia torulosa
State Rank Reason (see State Rank above)
Descurainia torulosa is a regional endemic that is extremely rare in Montana. The species is known from a single 1979 collection from Park County, where plants were found on an alpine talus slope. Population counts, extent, and trends are unknown. The habitat is largely intact and in good condition, but is adjacent or near to roads which in 2019 were reported to have invasive plant species.
Surveys to relocate the 1979 observation are greatly needed. If found, data on population parameters, habitat condition, and potential threats are essential to collect in order to refine and accurately assign a state conservation status rank. Surveys of potentially suitable habitat in adjacent areas are also needed to better understand the species' distribution and status in the state.
General Description
PLANTS: Short-lived perennials, somewhat to densely hairy all over. Stems few to many, arising from the base, generally not branched below and very seldom branched above, decumbent (Goodson and Al-Shehbaz in FNA 2010), 4–15 cm. Vestiture of stellate hairs (Lesica 2012).
LEAVES: Basal leaves: rosulate; petiole 3-14 mm; blade oblanceolate, 9-35 mm in length, the 3-5 pairs of blade lobes oblong to oblanceolate with smooth margins (FNA 2010). Stem leaves lacking petiole or short-petiolate; blades reduced distally (FNA 2010), 2–10 cm in length, oblanceolate, pinnate, the pinnae lobed to entire (Lesica 2012).
INFLORESCENCE: Racemes, growing significantly longer in fruit (Goodson and Al-Shehbaz in FNA 2010).
Phenology
Flowers June-July (FNA 2010).
Diagnostic Characteristics
Descurainia torulosa has clearly distally-curved fruits, is slightly pubescent and strongly torulose. Its stems (often several) are decumbent and unbranched.
The fruit of the similar
Descuraina incana is straight, glabrous, and barely or not at all torulose. Its simple stems are erect and branched (Goodson and Al-Shehbaz
in FNA 2010).
Species Range
Montana Range
Range Descriptions
Native
Range Comments
Endemic to western Wyoming and Park County, Montana.
Observations in Montana Natural Heritage Program Database
Number of Observations: 1
(Click on the following maps and charts to see full sized version)
Relative Density
Recency
(Observations spanning multiple months or years are excluded from time charts)
Habitat
Talus slopes in the subalpine zone within Montana (Lesica et al. 2012).
Ecological Communities Associated with this Species
Alpine
Alpine - Sparse and Barren
Reproductive Characteristics
Flowers: Sepals upright, somewhat yellow, hairy (Goodson and Al-Shehbaz in FNA 2010); petals yellow, 1–2 mm in length (Lesica 2012).
Fruit: Fruit clearly curved distally, slightly pubescent, erect or nearly (Goodson and Al-Shehbaz in FNA 2010), torulose (with bulges around and constrictions between the seeds), 6–15 mm in length, up to 1 mm in width, tapering at both ends; style 0.1–0.3 mm in length. Seeds 10 to 18 per locule in 1 row (Lesica 2012), reddish brown; pedicels upright or nearly so, straight, 1.5-3 mm in length (Goodson and Al-Shehbaz in FNA 2010).
Stewardship Responsibility
Threats or Limiting Factors
Reported threats to Montana’s only population of Wyoming Tansymustard are due to invasive plant species. A specimen of Wyoming Tansymustard was collected in 1979. In 2019, the Yellowstone National Park Botanist relayed that invasive plant species occur along the roads that are adjacent to or near to this plant's habitat.
References
- Literature Cited AboveLegend:
View Online Publication
Flora of North America Editorial Committee, eds. 2010. Flora of North America North of Mexico. Volume 7. Magnoliophyta: Salicaceae to Brassicaceae. Oxford University Press, Inc., NY. 832 pp.- 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?- 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.
- Web Search Engines for Articles on "Wyoming Tansymustard"
