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COSEWIC Assessment and Update Status Report on the Scouler’s Corydalis in Canada

Technical Summary

Corydalis scouleri

Scouler’s corydalis
Corydale de Scouler

Range of Occurrence in Canada: BC

Extent and Area Information

Extent of occurrence (EO)(km2)
- known occupied extent of occurrence
275 km2

- extent of occurrence including potential extent of occurrence
1100 km2

Specify trend in EO


Are there extreme fluctuations in EO?


Area of occupancy (AO) (km2)

- total area of surveyed populations
0.10 km2

- area of occupancy including estimated area of potential occupancy
0.243 km2

Specify trend in AO


Are there extreme fluctuations in AO?


Number of known or inferred current locations


Specify trend in #


Are there extreme fluctuations in number of locations?


Specify trend in area, extent or quality of habitat


Population Information

Generation time (average age of parents in the population)

Number of mature individuals

Ca. 848 000 stems estimated but likely >1 million when additional suitable but inaccessible habitat is considered

Total population trend:

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

None documented

Are there extreme fluctuations in number of mature individuals?


Is the total population severely fragmented?


Specify trend in number of populations


Are there extreme fluctuations in number of populations?


List populations with number of mature individuals in each: (see Table 2)       

Threats (actual or imminent threats to populations or habitats)

Limited impact from road and bridge construction, trampling by recreationalists, logging, flooding and inbreeding depression.

Rescue Effect (immigration from an outside source)

Status of outside population(s)?
USA: G4, frequent to common

Is immigration known or possible?

Unknown but unlikely

Would immigrants be adapted to survive in Canada?


Is there sufficient habitat for immigrants in Canada?


Is rescue from outside populations likely?


Quantitative Analysis

[provide details on calculation, source(s) of data, models, etc]


Current Status

COSEWIC: Threatened (2001)
COSEWIC: Not at Risk (2006)

Status and Reasons for Designation

Status: Not At Risk
Alpha-numeric code: Not applicable

Reasons for Designation: A conspicuous perennial herb of riverside habitats that is restricted to a small region of south-western Vancouver Island. The species was previously assessed as threatened but is now known to be present at additional locations and is much more abundant than previously documented. There is no evidence of population decline or fluctuation and no significant threats appear to affect the species. More than one-half of the population is now in protected areas specifically managed for this species and, since extensive areas of suitable habitat remain to be surveyed, additional populations will likely be discovered.

Applicability of Criteria

Criterion A (Declining Total Population):
NA. No evidence of decline > 30%.

Criterion B (Small Distribution, and Decline or Fluctuation):
NA. Extent of occurrence and area of occupancy below critical levels but > 5 sites and these not severely fragmented and no continuing decline or extreme fluctuations documented.

Criterion C (Small Total Population Size and Decline):
NA. Although actual numbers of discrete plants is unknown, with 848 000 stems estimated, and likely more to be found, it is highly likely that there are >>10 000 plants present.

Criterion D (Very Small Population or Restricted Distribution):
NA. There are >> 1000 plants and > 5 sites; although the area of occupancy is << 20 km2, there are no significant threats currently that would place the species at risk of becoming highly endangered in a short period of time. Recent fieldwork has confirmed that the population is more widely distributed than previously known; it is at least seven times larger than previous estimates and more than half of the population is now in protected areas managed specifically for this species. Additional suitable areas of difficult to access habitat also remain to be explored.

Criterion E: (Quantitative Analysis):
None available.