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Big Horn Fleabane - Erigeron allocotus
State Rank Reason (see State Rank above)
A regional endemic of Montana and Wyoming. In Montana, it is known only from the Pryor Mountain Desert - Bighorn Basin area of Carbon and Big Horn Counties. The species can be common in areas where it is found.
- Details on Status Ranking and Review
Population Size
Score0-1 - Moderate to Large: Population size is imprecisely known but is believed to be >10,000 individuals.
Range Extent
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
Area of Occupancy
Score2 - Low: Generally occurring in 4-10 Subwatersheds (6th Code HUC’s).
Environmental Specificity
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).
Trends
Score0-1 - Stable to Minor Declines:
CommentTrends are undocumented, but it does not appear that the species has experienced moderate or severe declines.
Threats
Score0 - Low: Impacts, if any, to the species are expected to be minor or insignificant (affecting <10% of populations) in severity, scope and immediacy.
CommentImpacts to some populations are possible from various, localized activities but the scope of any impacts would be very low.
Intrinsic Vulnerability
Score0-1 - Low to Moderate Vulnerability.
Raw Conservation Status Score
Score
6 to 9 total points scored out of a possible 19.
General Description
Taprooted perennial with a usually branched caudex. Stems ascending to erect, 5–10 cm. Herbage hirsute, minutely glandular. Leaves mainly basal; blades spatulate, 1–2 cm long, mostly 3-lobed at the tip. Heads 1 to 4, radiate. Involucres campanulate, 4–6 mm high; phyllaries in 2 to 3 series, glandular, sparsely hirsute. Rays white to pink, 20 to 40 ligules filiform, 3–6 mm long. Disk corollas ca. 3 mm long. Achenes ca. 2 mm long
(Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).
Phenology
Flowering in May to early July.
Diagnostic Characteristics
Erigeron compositus has leafless or almost leafless stems that are cleft into 5-10 narrow segments.
Species Range
Range Comments
Regional endemic of the Bighorn and Pryor ranges and adjacent foothills in north-central Wyoming and south-central Montana.
Observations in Montana Natural Heritage Program Database
Number of Observations: 60
(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
Stony, sparsely vegetated, limestone or calcareous sandstone-derived soil of exposed ridges and cliffs in the valleys and montane zone.
Ecological Systems Associated with this Species
- Commonly Associated with these Ecological Systems
Forest and Woodland Systems
Shrubland, Steppe and Savanna Systems
Sparse and Barren Systems
References
- Additional ReferencesLegend:
View Online Publication
Do you know of a citation we're missing?- Heidel, B.L. and W. Fertig. 2000. Rare plants of Bighorn Canyon National Recreation Area. Report to the National Fish and Wildlife Foundation and Bighorn Canyon National Recreation Area, National Park Service. Montana Natural Heritage Program and Wyoming Natural Diversity Database. Helena and Laramie. 63 pp. plus appendices.
- Lesica, P. and P.L. Achuff. 1992. Distribution of vascular plant species of special concern and limited distribution in the Pryor Mountain desert, Carbon County, Montana. Unpublished report to the Bureau of Land Management. Montana Natural Heritage Program, Helena, MT. 105 pp.
- Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
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