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Yellow montane violet (Viola praemorsa) COSEWIC assessment and status report: chapter 11

Technical Summary

Viola praemorsa ssp. praemorsa

yellow montane violet (praemorsa subspecies) -- violette jaune des monts (de la sous-espèce praemorsa)

Range of Occurrence in Canada:
British Columbia

Extent and Area information

Extent of occurrence (EO) (km²) :
450 km² using mapware tools to calculate non-marine areas within range of the variety in Canada
specify trend (decline, stable, increasing, unknown) :
decline
are there extreme fluctuations in EO (> 1 order of magnitude)?
no
area of occupancy (AO) [Actual area occupied is < 0.2 km²] :
14 km² based on 1x1 km grid; 56 km² based on a 2x2 km grid
specify trend (decline, stable, increasing, unknown) :
unknown
are there extreme fluctuations in AO (> 1 order magnitude)?
no
number of extant locations :
14
specify trend in # locations (decline, stable, increasing, unknown):
long-term decline but stable for past three generations/last 10 years
are there extreme fluctuations in # locations (>1 order of magnitude)?
no
habitat trend: specify declining, stable, increasing or unknown trend in area, extent or quality of habitat :
decline in quality

Population informatio

generation time (average age of parents in the population) (indicate years, months, days, etc.) :
probably between 3 and 6 years
number of mature individuals (capable of reproduction) in the Canadian population (or, specify a range of plausible values):
32,000-49,000
total population trend: specify declining, stable, increasing or unknown trend in number of mature individuals :
Unknown
if decline, % decline over the last/next 10 years or 3 generations, whichever is greater (or specify if for shorter time period)
are there extreme fluctuations in number of mature individuals
(> 1 order of magnitude)?
no
is the total population severely fragmented (most individuals found within small and relatively isolated (geographically or otherwise) populations between which there is little exchange, i.e., < 1 successful migrant / year)?
yes


list each population and the number of mature individuals in each

Populations and number of mature individuals
populations tend to fluctuate
Population Numbers
Victoria 1
885
Victoria 2
304
Oak Bay1
43
Saanich 1
86
Saanich 2
297
Saanich 4
7 
Saanich 5
56
Saanich 7
3
Duncan 1
33
Duncan 2
1,736
Duncan 3
20,400
Duncan 4
5
Saltspring 1
14
Saltspring 2
19,278


specify trend in number of populations (decline, stable, increasing, unknown) :

Decline mainly historical or prior to last 10 years
are there extreme fluctuations in number of populations
(>1 order of magnitude)?
no

Threats (actual or imminent threats to populations or habitats)

Actual threats:

Rescue Effect (immigration from an outside source)

does species exist elsewhere (in Canada or outside)?
yes
status of the outside population(s)?
secure
is immigration known or possible?
a very rare event
would immigrants be adapted to survive here?
likely
is there sufficient habitat for immigrants here?
yes

Quantitative Analysis

Current Status

COSEWIC: Threatened (2000) ; Endangered (2007)

Status and Reasons for Designation

Status: Endangered

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

Reasons for Designation: The subspecies is only known in Canadafrom southeastern Vancouver Island and the adjacent southern Gulf Islands where it occurs as 14 mainly small, localized populations that are highly fragmented. This short-lived perennial is restricted to Garry oak woodlands and maritime meadows where habitat is continuing to decline in quality due to such factors as the spread of exotic invasive grasses as well as the spread of trees and shrubs as a result of fire suppression.

Applicability of Criteria

Criterion A (Declining Total Population): Not applicable. No recent declines noted and populations fluctuate.

Criterion B (Small Distribution, and Decline or Fluctuation): Endangered .B1ab(iii)+2ab( iii). EO and AO are below maximum values and there are 14 severely fragmented extant populations with inferred continued decline of habitat quality due to such factors as spread of exotics and regeneration of woody plants that shade violet plants as a consequence of change in fire regimes.

Criterion C (Small Total Population Size and Decline): Not applicable. Population is too large.

Criterion D (Very Small Population or Restricted Distribution): Not applicable. Population size is too large; AO is > 50 km² based on a 2x2 km grid.

Criterion E (Quantitative Analysis): None available.

Rescue

Rescue effect is low. Although the species occurs outside of Canada and is secure, the nearest known populations are about 100 km distant and seeds lack adaptations for long-distance dispersal.

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