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Evermann Fleabane - Erigeron evermannii
State Rank Reason (see State Rank above)
Erigeron evermannii is very rare in Montana where the species is only known from two occurences in Ravalli County. These occurrences have not been visited since the 1960s to 1970s. Plants occur in remote, alpine habitats that are largely intact and in good condition; thus, it is presumed that populations could be relatively stable or have only experienced minor declines. Significant threats to Erigeron evermannii have not been identified, though the small number of occurrences puts the species at a greater risk for extirpation. In addition, the changing climate could pose long-term impacts to the population.
Precise mapping and surveys that bring forth information on distributions, population counts and viability, habitat condition, and threats are greatly needed to establish baseline conditions and accurate status assessments. In addition, surveys in potentially suitable habitat would help determine if other populations are present.
General Description
Evermann Fleabane is a dwarf perennial. Its stems reach up to 10 cm high and arise from a branched rootstock and from a long, deep-seated taproot. The glabrous basal leaves are up to 4 cm long, spoon-shaped, and rounded at the tips. The stem leaves are greatly reduced or lacking. The flowering heads are solitary at the ends of the stems. The rays that compose the petals of the flowering head are 6-10 mm long and white or occasionally light blue. The involucral bracts are 5-8 mm long, spreading hairy, and usually glandular. The achenes have 25-35 unequal-length bristles, forming a pappus, at the top.
Phenology
Flowering in July-August.
Diagnostic Characteristics
Erigeron is a large and difficult genus to distinguish. The tap-rooted habit, triple-nerved basal leaves, stem pubescence, almost complete absence of stem leaves, and the shifting talus habitat are good distinguishing characters for E. evermannii.
Species Range
Montana Range
Range Descriptions
Native
Range Comments
Central ID to southwest MT. Regional endemic.
Observations in Montana Natural Heritage Program Database
Number of Observations: 8
(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
Shifting talus slopes and dry, rocky meadows near or above timberline.
National Vegetation Classification System Groups Associated with this Species
Alpine
Alpine - Sparse and Barren
Alpine - Vegetated
Ecology
POLLINATORS The following animal species have been reported as pollinators of this plant species or its genus where their geographic ranges overlap:
Bombus bifarius,
Bombus centralis,
Bombus fervidus,
Bombus flavifrons,
Bombus huntii,
Bombus melanopygus,
Bombus mixtus,
Bombus rufocinctus,
Bombus occidentalis, and
Bombus insularis (Thorp et al. 1983, Wilson et al. 2010, Colla and Dumesh 2010, Koch et al. 2012).
Stewardship Responsibility
Threats or Limiting Factors
Evermann Fleabane is known from two occurrences in Montana, in which its rarity puts the species at very high risk of state extirpation. Threats have not been reported though climate change poses a potential risk to the population. The MTNHP conducted a species-level assessment using the Climate Change Vulnerability Index (CCVI) in 2021, which resulted in a Highly Vulnerable rating to climate change. Climate change including increased ambient temperatures, decreased snowpacks, and increased frequencies and severities of drought could have negative impacts on the species; however, field-based data on the timing and magnitude from climate change is not available.
References
- Literature Cited AboveLegend:
View Online Publication
Colla, S.R. and S. Dumesh. 2010. The bumble bees of southern Ontario: notes on natural history and distribution. Journal of the Entomological Society of Ontario 141:39-68.- Koch, J., J. Strange, and P. Williams. 2012. Bumble bees of the western United States. Washington, DC: USDA Forest Service, Pollinator Partnership. 143 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.
- Thorp, R.W., D.S. Horning, and L.L. Dunning. 1983. Bumble bees and cuckoo bumble bees of California (Hymenoptera: Apidae). Bulletin of the California Insect Survey 23:1-79.
- Wilson, J.S., L.E. Wilson, L.D. Loftis, and T. Griswold. 2010. The montane bee fauna of north central Washington, USA, with floral associations. Western North American Naturalist 70(2): 198-207.
- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?- Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 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.
- Web Search Engines for Articles on "Evermann Fleabane"
