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White meconella (Meconella oregana) COSEWIC assessment and status report: chapter 11

Technical Summary

Meconella oregana

White meconella: méconelle d'Orégon

Range of Occurrence in Canada:
Southern Vancouver Island and Gulf Islands

Extent and Area Information

Extent of occurrence (EO)(km²)
in Canada <2,500 km²
Specify trend in EO:
no change
Are there extreme fluctuations in EO?
no
Area of occupancy (AO):
50 – 100 m²
Specify trend in AO:
overall decreasing
Are there extreme fluctuations in AO?
no multi-year studies available
Number of known or inferred current locations:
five (5)
Specify trend in # :
no periodic monitoring available
Are there extreme fluctuations in number of locations?
unlikely
Specify trend in area, extent or quality of habitat:
area and quality of habitat decreasing

Population Information

Generation time (average age of parents in the population):
10-12 months
Number of mature individuals (in 2004):
3,300 – 3,500
Total population trend:
decreasing
% decline over the last/next 10 years or 3 generations.
no complete counts from earlier years
Are there extreme fluctuations in number of mature individuals?(see discussions of Abundance and Fluctuations on p. 10):
likely yes, in years with exceptional weather
Is the total population severely fragmented?
yes
Specify trend in number of populations: :
Long-term downward trend from 15 to 5 populations; no short-term trend (last 10 yrs) available, but see under ‘Fluctuations and Trends’: down; but no complete counts in earlier years
Are there extreme fluctuations in number of populations?
Unknown: Only one year with range-wide observations

List populations with number of mature individuals in each:

Threats (actual or imminent threats to populations or habitats)

  1. Habitat loss imminent through residential development
  2. habitat degradation in longer term through introduced plant species,
  3. habitat degradation through inappropriate recreational use

Rescue Effect (immigration from an outside source)

Status of outside population(s)?
USA
Washington S1S2;
Oregon S1;
California S1
Is immigration known or possible?
unlikely
Would immigrants be adapted to survive in Canada?
unknown
Is there sufficient habitat for immigrants in Canada?
yes, but habitat quality mostly poor/decreasing
Is rescue from outside populations likely?
unlikely

Current Status

COSEWIC: Endangered (May 2005)

Status and Reasons for Designation

Status:  Endangered

Alpha-numeric code:  A3c; B1ab (i, ii, iii, iv,v),c (iv) + 2ab; (i, ii, iii, iv, v); c(iv); C1 + 2b

Reasons for Designation: A globally threatened annual plant with a highly restricted Canadian range and area of occupancy present at only five locations within the naturally rare Garry Oak Ecosystem. Its populations, totalling fewer than 3,500 mature plants, fluctuate greatly with varying precipitation patterns and are at imminent risk of major losses from development within the highly urbanized range of the species. Its habitat has also been impacted by the spread of many exotic weedy plants.

Applicability of Criteria

Criterion A (Declining Total Population): Endangered A3c based on inferred loss of the two largest sites due to development within 10 years (71-75% loss).

Criterion B (Small Distribution, and Decline or Fluctuation): Meets Endangered B1 and B2a (5 sites) b (i,ii,iii,iv,v), c (iv). The extent of occurrence and area of occupancy are below critical levels, with only 5 populations extant and continuing decline in area, extent and/or quality of habitat based on spread of alien species and inferred decline and or loss of at least the largest population to development; four consecutive year population data on one site indicates that extreme population fluctuation occurs and is likely related to climatic fluctuation (especially precipitation patterns).

Criterion C (Small Total Population Size and Decline): Endangered C1 and C2b. Although population size in 2004 was estimated as 3300-3500 mature plants, it is clear from the monitoring of the second largest population over a four-year period that extreme fluctuations occur. On this basis, there were likely fewer than 2500 plants in the year 2000 when this site had only 60 plants. The lower estimate must be accepted when dealing with species that fluctuate greatly. A decline is inferred based on the imminent loss of the two largest populations if a housing development proceeds.

Criterion D (Very Small Population or Restricted Distribution): Threatened D2 based on the occurrence of only 5 sites and a very small area of occupancy of perhaps <100 m² with imminent risk of loss inferred for the two largest populations.

Criterion E (Quantitative Analysis): Insufficient data.

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