Dwarf woolly-heads, specific populations, COSEWIC assessment status report: chapter 11

Technical Summary - Southern Mountain population

Note: The Vascular Plant Specialists of the Subcommittee for Plants and Lichens (COSEWIC) recognizes two separate designatable units within this species. These are geographically disjunct, present in two different COSEWIC ecological areas, and are subject to very different levels of risk based, in particular, on marked differences in the number of populations present in each unit.

Psilocarphus brevissimus: Southern Mountain population

Dwarf woolly-heads (Southern Mountain population) – psilocarphe nain (Population des montagnes du Sud)

Occurrence:

British Columbia

Extent and Area information

Extent of occurrence (EO)

[estimated using OziExplorer mapware area calculation] < 2 km²

Specify trend :

unknown

Are there extreme fluctuations in EO :

no

Area of occupancy (AO)

[estimated from summing up area occupied by individual occurrences and estimating missing values] : 0.1 ha

Specify trend in AO :

unknown

Are there extreme fluctuations in AO :

probably

Number of known or inferred current locations :

3

Specify trend in # :

unknown

Are there extreme fluctuations in number of locations?

perhaps

Specify trend in area, extent or quality of habitat :

unknown

Population information

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

4 months

Number of mature individuals :

700 – 2,000,000 depending on the year

Total population trend :

Southern Mountain population

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

n/a

Are there extreme fluctuations in number of mature individuals?

yes

Is the total population severely fragmented?

yes

Specify trend in number of populations :

unknown

Are there extreme fluctuations in number of populations? :

unknown

List populations with number of mature individuals in each:

  1. 30-300
  2. 225 – 2 million
  3. 450 – 7,700

Threats (actual or imminent threats to populations or habitats)

Potential threats - ATV use, herbicide weed control measures, changes in hydrology due to land use practices, and increased land development in the region.

Rescue Effect (immigration from an outside source)

Status of outside population(s)?.

The species is not ranked in Washington but S2 in Idaho and Montana

Is immigration known or possible?

Immigration is possible but probably occurs so rarely that it has no significance to rescue over periods of less than at least a few decades

Would immigrants be adapted to survive in Canada?

unknown

Is there sufficient habitat for immigrants in Canada?

yes

Is rescue from outside populations likely?

no

Quantitative Analysis

Not available

Current Status

COSEWIC: Endangered (2006)

Status and Reasons for Designation

Status: Endangered

Alpha-numeric code: B1ac(iv) + 2ac(iv)

Reasons for Designation: An annual herb restricted to a very small range and present at only three small sites on private lands within the COSEWIC Southern Mountain Ecological Area of British Columbia. Population size is subject to extreme fluctuations in the number of mature individuals due to variation in precipitation levels and the population is at risk from such factors as increased land development in the region and land use practices.

Applicability of Criteria

  • Criterion A: (Declining Total Population): No decline data
  • Criterion B: (Small Distribution, and Decline or Fluctuation): Met Endangered  B1ac(iv) + 2ac(iv) since both extent of occurrence and area of occupancy are well below critical values, only three sites are known and populations of this annual species undergo extreme fluctuations in area of occupancy and number of mature individuals.
  • Criterion C: (Small Total Population Size and Decline): Not applicable. Population size is too large.
  • Criterion D: (Very Small Population or Restricted Distribution): Met threatened D2 based on the presence of only three sites and a very small area of occupancy well below 20 km² with several threats documented in an area undergoing rapid urban expansion..
  • Criterion E: (Quantitative Analysis): Not available.

Page details

Date modified: