Mountain holly fern (Polystichum scopulinum) COSEWIC assessment and status report: chapter 11

Technical Summary

Polystichum scopulinum

Mountain Holly Fern – Polystic des rochers

Range of Occurrence in Canada:

British Columbia (BC), Quebec (QC) and Newfoundland & Labrador (NL) (on the Island of Newfoundland)

Extent and Area Information

Extent of occurrence (EO) (km²):

[approximate area within which the fern occurs, e.g., in BC a band of  0.1 km x 4 km]

  • BC: 0.4 km²
  • QC: 0.08 km²
  • NL: uncertain, but likely quite small

Specify trend in EO :

Stable

Are there extreme fluctuations in EO?

No

Area of occupancy (AO) (km²) :

[total area occupied by the fern]

  • BC: 0.01 km²
  • QC: 0.003 km²
  • NL: uncertain but likely quite small

Specify trend in AO :

Stable in BC and QC and likely so in the remote area of the Newfoundland site

Are there extreme fluctuations in AO?

No

Number of known or inferred current locations

  • BC: 1 area (3 pops.)
  • QC: 1 area (1 pop.)
  • NL: uncertain status of 1 historic population

Specify trend in # :

Stable

Are there extreme fluctuations in number of locations?

No

Specify trend in area, extent or quality of habitat :

Stable

Population Information

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

Unknown (several years)

Number of mature individuals

>250 and likely <1000 but no data are available for the Newfoundland site

Total population trend :

Likely stable

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

N/A

Are there extreme fluctuations in number of mature individuals?

No

Is the total population severely fragmented? (Widely disjunct in Canada and in BC disjunct by 230 km from WA state population; occurs sporadically and not at all serpentine locations and reproduction is likely almost exclusively vegetative since the relatively dry habitat is not conducive to spore germination and sexual reproduction) :

Yes

Specify trend in number of populations:

Stable

Are there extreme fluctuations in number of populations?

No

List populations with number of mature individuals in each:

  • BC: 412;
  • QC: 215;
  • NL: unknown

Threats (actual or imminent threats to populations or habitats)

  • BC: potential road building and mining exploration and forest fires
  • QC: the species and its habitat are legally protected and under no imminent threat of extirpation although plants occur along a trail and may be subject to trampling
  • NL: site is relatively inaccessible and the population, if extant, is likely under no imminent threat

Rescue Effect (immigration from an outside source)

Status of outside population(s)?

USA: secure (G5)

Is immigration known or possible?

Possible but unlikely

Would immigrants be adapted to survive in Canada?

Unknown

Is there sufficient habitat for immigrants in Canada?

Possibly

Is rescue from outside populations likely?

Unlikely

Quantitative Analysis

[provide details on calculation, source(s) of data, models, etc.] : N/A

Current Status

COSEWIC: Threatened (May 2005)

Status and Reasons for Designation

Status:  Threatened

Alpha-numeric code:  Met criteria for Endangered, B1ab(iii,v)+2ab(iii,v), but designated Threatened because of the uncertainty about the imminent threats from mining activities at the British Columbia sites. The species is also protected in Quebec. Criteria met for Threatened: B1ab(iii,v)+2ab(iii,v); C2a(i); D1+2.

Reasons for Designation: A fern of very restricted occurrence on serpentine substrates in three widely separated areas of Canada. These very small populations are at risk from stochastic events and, the 3 in British Columbia, from potential mining activities for precious metals.

Applicability of Criteria

Criterion A (Declining Total Population): N/A

Criterion B (Small Distribution, and Decline or Fluctuation): Meets Endangered B1ab(iii,v)+2ab(iii,v) with highly restricted disjunct occurrences at 3 locations (the BC populations could all be impacted by mining and so are considered as a single location with three populations); a continuing decline is inferred if mining is undertaken at the BC populations with subsequent loss in habitat extent, quality and likely loss of plants; imminence of threat to the BC population is uncertain (no mining initiated since 2001 when mine holdings were promoted). A potential threat exists at the QC site due to hiking activities on a trail through the population. However, since the species is not likely to be completely eradicated along the 4 km stretch of serpentine in BC if mining were to be initiated and the species is also protected in QC, a status of threatened is recommended.

Criterion C (Small Total Population Size and Decline): Threatened C2a(i). Recent declines have not been demonstrated but can be inferred if mining occurs at the BC location; no populations contain >1,000 mature individuals. This is inferred from the fact that seemingly the Newfoundland population, if extant, is likely highly restricted and judging by numbers at the BC and QC localities likely is also relatively small.

Criterion D (Very Small Population or Restricted Distribution): Meets threatened D1 with <1000 plants in total and D2 with <5 locations that are highly fragmented and with a very small area of occupancy (<20km² in total) and at risk from potential mining activities in BC and possible trampling in QC.

Criterion E (Quantitative Analysis): Not applicable.

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