Yellow montane violet (Viola praemorsa) COSEWIC assessment and status report: chapter 7
Population Sizes and Trends
Search effort
Suitable sites have been surveyed repeatedly since the early 1980s in a series of projects designed to document the distribution of rare plants of Garry oak woodlands and maritime meadows on southeast Vancouver Island and the southern Gulf Islands. The principal investigators included Adolf and Oldriska Ceska, Matt Fairbarns, Hans Roemer, Jenifer Penny, Harvey Janszen, Frank Lomer and the late George Douglas, all of whom are/were familiar with the yellow montane violet. These investigators have examined a number of areas beyond the documented range of yellow montane violet but failed to document any significant range extensions.
Over 90 sites with Garry oak woodlands and maritime meadows have been investigated (Figure 4) and much of it has been surveyed more than once during this period. During the past decade alone, over 500 person-days have been spent searching for rare species in suitable habitats. Despite the concentrated effort, only one new population of yellow montane violet has been discovered, since 1997 (Duncan 4). Private lands and Indian reserves, which only constitute a small proportion of the apparently suitable habitat, have not been surveyed as thoroughly as public lands.
Figure 4. Search effort for yellow montane violet, 2001-2006.
Abundance
In the absence of information on rates of genetic exchange, occurrences of yellow montane violet more than 1,000 m apart are treated as separate locations. On this basis, it has been validly1 reported from 18-19 locations in British Columbia (Table 1). The uncertainty lies in the fact that the populations at Saanich 3 and Saanich 6 are too vaguely reported to determine if they were more than 1,000 m apart (both appear to be extirpated). Fourteen populations are extant. Some populations consist of multiple subpopulations (i.e. patches separated by <1,000 m).
Location | Year | Collector/observer | Number of plants/area | Land ownership/notes |
---|---|---|---|---|
Victoria | 1897 | Henry | unknown | location too vague |
Victoria 1 | 1913 1993 1994 1997 2006 |
Macoun Douglas Douglas Douglas Fairbarns |
unknown 400-450/1,100 m² 100-150/50 m² 465/1,000 m² 885/525 m² |
municipal park |
Victoria 2 | 1972 1993 1994 1997 2006 |
Roemer Douglas Ryan & Douglas Douglas Fairbarns |
unknown unknown 500/? 490/435 304/2,500 m² |
municipal park |
Oak Bay 1a | 1994 1997 2004 2006 |
Douglas Douglas Fairbarns Fairbarns |
125/18 m² 95/18 m² 25-30/6 m² 41/8 m² |
municipal park |
Oak Bay 1b | 2004 2006 |
Fairbarns & Penny Fairbarns |
10/5 m² 2/6 m² |
municipal park |
Oak Bay 2 | 1963 1993 2003 2006 |
Young Ryan and Douglas Ceska and Ceska Fairbarns |
unknown failed to find failed to find failed to find |
municipal park |
Saanich 1 | 1971 1995 2001 |
Roemer Lee Penny |
unknown 2/1 m² 86/<100 m² |
municipal park |
Saanich 2 | 1997 2000 2006 |
Roemer Douglas Fairbarns |
unknown 282/305 m² 297+/- 20/1,874 m² |
municipal park |
Saanich 3 | 1887 | Macoun | unknown | unknown |
Saanich 4 | 1994 1996 1997 1999 2000 2001 2002 2006 2006 |
Ryan Mothersill Douglas Mothersill Mothersill Mothersill Mothersill Fairbarns Roemer |
40/27 m² 20/2 m² 59/10 m² 12/? 15/? 17/? 17/? 7/20 m² 7/5 m² |
municipal park |
Saanich 5 | 1997 2000 2001 2006 |
Fraser Fraser Fraser Fairbarns |
111 66 78/10 m² 56/12 m² |
regional park |
Saanich 6 | 1947 | Unknown | unknown | unknown |
Saanich 7 | 1919 2003 2005 |
Newcombe Fairbarns & Roemer Fairbarns |
unknown 1/27 m² 3/27 m² |
private property |
Saanich 8 | 1964 1987 1995 2001 |
Hett Ring Golinksi Hartwell |
unknown unknown failed to find failed to find |
|
Duncan 1 | 1993 1994 1997 2006 |
Douglas Douglas Douglas Fairbarns |
unknown 25/100 m² 56/120 m² 33/50 m² |
ecological reserve |
Duncan 2 | 1933 1997 1998 2000 2006 |
Newcombe Douglas Douglas Douglas MacDougall |
unknown >6,400/1,000 m² 6,940/? 3,205/12,373 m² 1,736 +/-100/? |
NGO conservation reserve |
Duncan 3 | 1992 1993 1997 2003 2004 2005 2006 2007 |
Ceska Douglas Douglas Roemer and Fairbarns Roemer and Fairbarns Roemer and Fleming Roemer and Fleming Fleming |
unknown unknown 45,000/5,700 m² 10,000 28,700/4,320 m² 16,300/3,100 m² 10,700/2,350 m² 20,400 |
NGO conservation reserve |
Duncan 4 | 2004 | Douglas and Smith | 5/? | church |
Saltspring 1 | 1985 2006 |
Roemer McIntosh & Linton |
unknown 14/100 m² |
provincial park |
Saltspring 2 | 1993 1996 1999 2005 2007 |
Chatwin Penny Lomer Roemer2 Annschild |
>300/400 m² 200/2,500 m² 200-300/? 200/50 m² 19,278 plants: 14,096 on Transport Canada lands and 5,182 on provincial crown lands and private lands; population occupies approximately 10 ha |
mixed (Transport Canada, provincial crown land and private land) |
Nanoose Hill | 1976 1973 2005 |
Douglas Douglas Fairbarns |
unknown failed to find failed to find |
private or federal? |
Comox | 1961 1993 |
Beamish Cadrin |
unknown failed to find |
regional park? |
Table 1 cites first record, most recent observation, any other observations with reliable population estimates and (where applicable) subsequent unsuccessful surveys.
Based on recent data from each of the sites, the total British Columbia population size is between 32,000 and 49,000 plants with approximately 80-90% of the subspecies’ population concentrated in the two largest populations, at Duncan 3 and Saltspring 2.
Fluctuations and trends
The number of populations has been in slow decline – five to six populations have disappeared over the past century but none of these have been lost over the past 10 years. In most cases records are not adequate enough to determine when populations disappeared, but four of the populations appear to have been lost between 1961 and 1995.
Although Victoria 1 and Saltspring 2 appear to be increasing, the change in numbers is actually a result of the discovery of unreported subpopulations and more careful searches of known subpopulations. Anecdotal evidence suggests that the larger populations fluctuate substantially. The best documented fluctuation is at Duncan 3, where numbers have fluctuated between 10,000 and 28,000 (using a constant technique and coordinated observers) from 2003-2007.
There is no clear trend in the extent of the actual area of habitat occupied, probably because of inconsistencies in methods of estimation among observers. The quality of the area of occupancy is declining, primarily as the result of invasion by exotic plants.
Rescue effect
Yellow montane violet is not known from the nearby San Juan Islands(Atkinson and Sharpe 1993, D. Giblin pers. comm. 2006) or the Olympic Peninsula (Buckingham et al. 1995). The nearest population is about 100 km away, near Tacoma, Washington (Burke Museum of Natural History and Culture 2006). The status of the U.S. population of yellow montane violet is uncertain (see “Existing protection or other status”). Given the very limited ability of this species to disperse over distances of more than a few metres, the British Columbia population is very unlikely to be rescued by natural circumstances.
1 The Metchosin record has been rejected as explained in Table 1.
2 Further surveys needed to determine if there are undiscovered subpopulations at this location.
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