Coast Microseris (Microseris bigelovii) COSEWIC assessment and status report: chapter 11

Technical Summary

Microseris bigelovii

coast microseris – microséris de Bigelow

Range of Occurrence in Canada:

British Columbia

Extent and Area Information

Extent of occurrence (EO) (km²)

(Coastal strip 400 km long with maximum inland occurrence of 50 m from shore) : about 20 km²

Specify trend in EO :

stable

Are there extreme fluctuations in EO?

no

Area of occupancy (AO) (km²) (actual area of habitats occupied) :

<<1 km² (<1 hectare)

Specify trend in AO :

long-term decline, short-term stable

Are there extreme fluctuations in AO?

no

Number of known or inferred current locations :

6

Specify trend in # :

long-term decline, short-term stable

Are there extreme fluctuations in number of locations?

no

Specify trend in area, extent or quality of habitat :

declining in both area and quality

Population Information

Generation time (average age of parents in the population) :

8-10 months

Number of mature individuals :

5,500-6,500

Total population trend:

long-term decline; short-term stable

% decline over the last/next 10 years or 3 generations.

no reliable information

Are there extreme fluctuations in number of mature individuals?

possibly

Is the total population severely fragmented?

yes, most populations unlikely to have any exchange even over longer periods

Specify trend in number of populations :

declining (over half the known populations have disappeared in the past 130 years)

Are there extreme fluctuations in number of populations?

  • no
  • Hornby Island: 2,000 – 2,500
  • OakBay #1: 1,500 – 2,000
  • OakBay #2: 190
  • Esquimalt: 530
  • Rocky Point #1: 50
  • Rocky Point #2: 1,250

Threats (actual or imminent threats to populations or habitats)

  • Existing threats: recreational use, park facility development, invasive species, loss of potential habitat
  • Potential threats:  marine pollution

Rescue Effect (immigration from an outside source)

none

Status of outside population(s)?

USA:  extirpated in Washington, imperiled in Oregon

Is immigration known or possible?

unknown and not likely

Would immigrants be adapted to survive in Canada?

uncertain

Is there sufficient habitat for immigrants in Canada?

very limited

Is rescue from outside populations likely?

no

Quantitative Analysis

[provide details on calculation, source(s) of data, models, etc] : none possible

Current Status

COSEWIC: Endangered, 2006

Status and Reasons for Designation

Status:  Endangered

Alpha-numeric code:  B1ab (ii, iii) + 2ab (ii, iii)

Reasons for Designation: A small annual herb present in a few fragmented sites within a narrow coastal fringe on southeast Vancouver Island in a densely inhabited urbanized region. Development, recreational activities, site management practices and competition from invasive alien plants continue to impact the species.

Applicability of Criteria

  • Criterion A: (Declining Total Population): Not applicable (n/a)
  • Criterion B: (Small Distribution, and Decline or Fluctuation): Meets Endangered B1ab (ii, iii) + 2ab (ii, iii) based on extent of occurrence and area of occupancy much below critical criterion values, present at only 6 highly fragmented sites and continuing decline inferred in area of occupancy and quality of habitat due to the spread of exotic shrubs and herbs; no specific data are available on extreme fluctuations of this annual plant.
  • Criterion C: (Small Total Population Size and Decline): n/a Population size estimated at 5,500-6,500 but the degree of population decline has not been clearly identified and some populations consist of >1,000 plants.
  • Criterion D: (Very Small Population or Restricted Distribution): Meets Threatened D2 due to the small area of occupancy and the presence of ongoing impacts from the spread of exotic plants and site management practices.

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