Short-rayed alkali aster (Symphyotrichum frondosum) COSEWIC assessment and status report: chapter 11
Technical Summary
Symphyotrichum frondosum
short-rayed alkali aster – aster feuillu
Range of Occurrence in Canada:
British Columbia
Extent and Area Information
Extent of occurrence (EO) (km²)
Estimate based on measuring distance from the most northerly station to the most southerly station, and assuming an average width of potential habitat of 1 km (e.g., shorelines on east/west sides of lakes, meandering rivers, adjacent lakes within valley). 56 km²
Specify trend in EO :
Unknown
Are there extreme fluctuations in EO?
Unknown, but unlikely
Area of occupancy (AO) (km²)
Estimate based on actual areas of habitat known to be occupied. Likely << 1 km² (900 m², based on limited field observations)
Specify trend in AO :
Possibly a small decline with loss of one very small sub-population
Are there extreme fluctuations in AO?
Unknown
Number of known or inferred current locations :
4
Specify trend in # :
Stable
Are there extreme fluctuations in number of locations?
No
Specify trend in area, extent or quality of habitat
Population Information
Generation time (average age of parents in the population) :
Annual species
Number of mature individuals
<1,000, but can fluctuate year-to-year
Total population trend:
Declining
% decline over the last/next 10 years or 3 generations.
Cannot determine.
Are there extreme fluctuations in number of mature individuals?
Unknown, but there are year-to-year variations.
Is the total population severely fragmented?
No
Specify trend in number of populations:
Stable
Are there extreme fluctuations in number of populations?
Unknown
List populations with number of mature individuals in each:
Threats (actual or imminent threats to populations or habitats)
Current main impacts are from trampling, beach management practices and invasive plants
Potential major impact could result from the development of a shoreline facility at Osoyoos L.
Rescue Effect (immigration from an outside source)
Status of outside population(s)?
USA: Montana: Critically Imperiled, Wyoming: Imperiled, SNR in 10 other states, including Washington
Is immigration known or possible?
possible, but unlikely
Would immigrants be adapted to survive in Canada?
likely
Is there sufficient habitat for immigrants in Canada?
Yes
Is rescue from outside populations likely?
Unlikely
Quantitative Analysis
Not applicable.
Current Status
COSEWIC:Endangered (2006).
Status and Reasons for Designation
Status: Endangered
Alpha-numeric code: B1ab (ii, iii, iv, v) + 2ab(ii, iii, iv, v)
Reasons for Designation: An annual herb of lake shorelines present at only a few remaining sites in restricted habitats. The small populations are subject to disruption from such activities as trampling, beach management, spread of invasive plants and potential development of a major facility at one of the primary sites.
Applicability of Criteria
Criterion A: (Declining Total Population): Not applicable. No specific data to show decline versus fluctuation.
Criterion B: (Small Distribution, and Decline or Fluctuation): Meets Endangered B1ab (ii, iii, iv, v) + 2ab(ii, iii, iv, v) with very small extent of occurrence and area of occupancy, presence of only 4 localities and decline in area of occupancy, quality of habitat, number of populations and mature plants that can be inferred based on the current threat of shoreline development.
Criterion C: (Small Total Population Size and Decline): Not applicable. Although < 1,000 plants may be present during years of suitable water levels, a future loss of 20% cannot be inferred. At least one population is known to have > 250 mature plants in some years, and 95% of the plants may be in one population; however, this is difficult to determine with large fluctuations in population size.
Criterion D: (Very Small Population or Restricted Distribution): Meets Threatened D1 and D2 with likely <1,000 mature plants during years of high water levels and presence of only 4 localities and a very small area of occupancy with a series of current threats and a major potential threat known.
Criterion E: (Quantitative Analysis): Not available.
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