Dwarf sandwort (Minuartia pusilla) COSEWIC assessment and status report: chapter 11
Technical Summary
Minuartia pusilla
Dwarf sandwort – minuartie naine
Range of Occurrence in Canada:
British Columbia
Extent and Area Information
Extent of occurrence (EO) (km²)
<< 1 km² (10 m²)
Specify trend in EO :
Stable
Are there extreme fluctuations in EO?
Unknown
Area of occupancy (AO) (km²)
<< 1 km² (10 m²)
Specify trend in AO :
Stable
Are there extreme fluctuations in AO?
Unknown
Number of known or inferred current locations :
1
Specify trend in # :
Stable
Are there extreme fluctuations in number of locations?
No
Specify trend in area, extent or quality of habitat :
Decline is likely based on impacts of trampling and disturbance by gulls
Population Information
Generation time (average age of parents in the population) :
1 year (< 6 months)
Number of mature individuals :
9 (in 2002) but variable in number and maintained at low levels
Total population trend:
Unknown
% decline over the last/next 10 years or 3 generations.
Numbers likely fluctuate yearly
Are there extreme fluctuations in number of mature individuals?
Unknown but possible at very low levels of population size
Is the total population severely fragmented?
Yes (disjunct from populations in NW USA)
Specify trend in number of populations :
Stable
Are there extreme fluctuations in number of populations?
None (1 population)
List populations with number of mature individuals in each:
9 plants at the single population
Threats (actual or imminent threats to populations or habitats)
- imminent: invasive species competition; climate change (drying trends)
- actual: trampling by boaters, wave action, and diggings by gulls
Rescue Effect (immigration from an outside source)
Status of outside population(s)?
USA: Stable
Is immigration known or possible?
Unlikely
Would immigrants be adapted to survive in Canada?
Unknown
Is there sufficient habitat for immigrants in Canada?
Probably
Is rescue from outside populations likely?
No
Quantitative Analysis
Not Applicable
Other Status
Status and Reasons for Designation
Status: Endangered
Alpha-numeric code: D1
Reasons for Designation: An annual ephemeral herb present at a single very small vernal seepage site along a rocky maritime headland in southern Vancouver Island highly disjunct from the nearest populations in southern Washington State. The maximum population size documented totals 20 plants with numbers likely fluctuating depending on precipitation patterns. Risks to the plants arise from the susceptibility of the single small population to stochastic events and on-going disturbance of the habitat by gulls, trampling by boaters and potentially from encroaching invasive plants.
Applicability of Criteria
- Criterion A (Declining Total Population): Likely not applicable due to naturally fluctuating population size
- Criterion B (Small Distribution, and Decline or Fluctuation): N/A. Small EO and AO but decline not evident due to fluctuation in numbers of the few plants documented.
- Criterion C (Small Total Population Size and Decline): N/A. Small population that fluctuates but no decline evident.
- Criterion D (Very Small Population or Restricted Distribution): Endangered under D1 due to presence of <250 plants
- Criterion E (Quantitative Analysis): N/A
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