BC Conservation Data Centre: Conservation Status Report
Castilleja victoriae
Victoria's owl-clover
| Scientific Name: | Castilleja victoriae |
|---|---|
| English Name: | Victoria's owl-clover |
| Provincial Status Summary | |
| Status: | S1 |
| Date Status Assigned: | January 26, 2007 |
| Date Last Reviewed: | April 30, 2019 |
| Reasons: | Castilleja victoriae is an endemic species with an extremely narrow range of distribution. There are only two to three extant populations, and only a portion of one of these populations is afforded protection within an Ecological Reserve. One of the populations may have recently been lost. Four populations have been lost since the turn of the last century. Habitat loss and degradation due to development, recreational activities and invasive species preclude the possibility of range expansion, and pose threats to the continued existence of the extant populations. |
| Range | |
| Range Extent: | A = <100 square km |
| Range Extent Comments: | Castilleja victoriae is restricted to a small area on southeast Vancouver Island in the immediate vicinity of Victoria. Globally, it extends east to the San Juan Islands of Washington State, where a single population has been recorded. |
| Area of Occupancy (km2): | AC = 1-5 |
| Area of Occupancy Comments: | As of 2006, the total area of occupancy of the two extant populations was less than 610 square metres (M. Fairbarns, pers. comm. 2006). Using a 2 km x 2 km grid analysis, the area of occupancy is 4 grids or 16 sq km. |
| Occurrences & Population | |
| Number of Occurrences: | A = 1 - 5 |
| Comments: | Based on 2006 data, and accepting the criterion that plants more than 1 kilometre apart constitute separate populations, there are two or three extant populations, all in the Oak Bay area of Victoria: Trial Island, Harling Point and Cattle Point. The Cattle Point population has not been observed since 2004 and may be extirpated. Two other Oak Bay populations, at Ten Mile Point and Lesser Trial Island, have not been observed since the 1950s and are presumed to be extirpated. Three other historical collections, from the Chain Islets, Dallas Road and the Shawnigan area are extirpated. The Shawnigan collection is out of range for the species and may be a mis-labelled specimen (M. Fairbarns, pers. comm. 2006). |
| Number of Occurrences with Good Viability / Ecological Integrity: | B = 1 - 3 |
| Comments: | Only one population, Trial Island, has good viability. It is the largest known population (6,000 - 7,000 plants) and occurs on an Ecological Reserve, where it is offered a significant level of protection. |
| Number of Occurrences Appropriately Protected & Managed: | B = 1 - 3 |
| Comments: | The Trial Island population is afforded a significant level of protection, as part of the population occurs within an Ecological Reserve. Since the species has not been officially recognized and assessed and listed, it is not yet protected under the Species At Risk Act where it occurs on federal land at a National Historic Site (Harling Point). |
| Population Size: | E = 2,500 - 10,000 individuals |
| Comments: | In 2006, there were two extant populations with a sum of 6,000 - 7,000 mature individuals (Trial Island and Harling Point). Approximately 98% of the global population is found on Trial Island, which consists of up to nine subpopulations in favourable years. The largest of these comprised approximately 4,200 individuals in 2001 but rose to 6,456 individuals in 2006. Several of the smaller subpopulations completely disappear in poor years, presumably persisting in the soil seed bank. Two other populations have been reported in recent years, but one of these (Cattle Point) may have become extirpated as no plants have been observed over the past three years (2005, 2006 and 2007) and the population numbered less than 10 plants in each of the two previous years. The third Canadian population (Harling Point) has fluctuated greatly, but consisted of less than 50 individuals in 2006 and occupied an area of approximately 8 square metres. |
| Threats (to population, occurrences, or area affected) | |
| Degree of Threat: | Substantial, imminent threat |
| Comments: |
Habitat loss has been the leading factor in the disappearance of populations. Recreational activities, including trampling, bicycle use and dog activity are a major threat to extant populations, two of which (Cattle Point and Harling Point) occur in parks subject to extremely heavy use. Aggressive alien plants have invaded existing and potential habitat for Castilleja victoriae. Microsites in vernal pool environments are often dominated by a carpet of Spergularia rubra during flowering season. The margins of the vernal pools and seeps, where C. victoriae tends to be most abundant, are often dominated by invasive annual grasses such as Agrostis capillaris, Aira praecox, Bromus hordeaceus, Hordeum spp., Poa annua and Vulpia bromoides. Slightly drier areas tend to be dominated by a dense sward of invasive grasses including Anthoxanthum odoratum, Dactylis glomerata, Holcus lanatus and Lolium perenne as well as introduced forbs such as Geranium molle, Hypochaeris radicata, Plantago lanceolata, Rumex acetosella and Silene gallica. These exotic species appear to have displaced a native bunchgrass community dominated by Danthonia californica and Deschampsia cespitosa, and taken over open areas between the bunchgrasses where C. victoriae may once have thrived. The Chain Islands population was probably lost as a result of invasive species, as most upland habitats on the islands have been overtaken by annual grasses such as Poa annua. All extant populations occur just above sea level along heavily-used shipping lanes. Thus, there is also a constant threat of oil spills and other types of marine pollution in their coastal environments (M. Fairbarns, pers. comm. 2006). |
| Trend (in population, range, area occupied, and/or condition of occurrences) | |
| Short-Term Trend: | DE = Decline of 30-70% |
| Comments: | Two of the five populations know to exist in the 1950s are now extirpated, and one that persisted until at least 2003 is potentially extirpated. |
| Long-Term Trend: | D = Decline of 50-70% |
| Comments: | Extensive urban and residential development occurred in the primary habitat of Castilleja victoriae before the species was extensively inventoried, so the magnitude of long-term population trends is unknown. Nevertheless, five or six of the eight populations reported in BC have become extirpated since the species was first collected in the late nineteenth century (M. Fairbarns, pers. comm. 2006). |
| Other Factors | |
| Intrinsic Vulnerability: | A=Highly vulnerable |
| Comments: | Castilleja victoriae has high intrinsic vulnerability because despite its high fecundity, it appears to be a very weak disperser and is unlikely to recolonize sites once extirpated. |
| Environmental Specificity: | B=Narrow. Specialist or community with key requirements common. |
| Comments: |
Castilleja victoriae has an extremely limited range and exhibits highly specific habitat requirements, being restricted to vernal seeps and the margins of vernal pools within 50 metres of the ocean in the immediate vicinity of Victoria. This habitat type is now exceedingly scarce and subject to competition from aggressive invasive species. |
| Other Rank Considerations: | |
| Information Gaps | |
| Research Needs: | |
| Inventory Needs: | There have been extensive, directed inventories for Castilleja victoriae (under its former designation as C. ambigua ssp. ambigua) and it is unlikely that further populations will be discovered. The existing populations should be closely monitored, however, to assess their ongoing health and vigour. |
| Stewardship | |
| Protection: | It is critical that effective protective measures be instituted at the extant populations. As of 2006, Castilleja victoriae is a undescribed species (Fairbarns and Egger, 2007), but has not been assessed by COSEWIC or protected by any species at risk legislation (M. Fairbarns, pers. comm. 2006). When the species is designated a Species At Risk, the small population on a National Historic Site (Harling Point) will be subject to the stipulations of the Species At Risk Act, but a recovery plan will be essential if the population is to survive. |
| Management: | Institution of recovery plans and protective measures by the municipal, provincial and federal governments. |
| Version | |
| Author: | Fairbarns, M. and S.Hartwell |
| Date: | April 07, 2009 |
| References | |
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Fairbarns, M. 2005l. Distribution and Status of Castilleja ambigua ssp. ambigua on the West Coast of Vancouver Island. Prepared by Aruncus Consulting for Parks Canada Agency/British Columbia Conservation Data Centre.
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Please visit the website Conservation Status Ranks for information on how the CDC determines conservation status ranks. For global conservation status reports and ranks, please visit the NatureServe website http://www.natureserve.org/.
Suggested Citation:
B.C. Conservation Data Centre. 2009. Conservation Status Report: Castilleja victoriae. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Apr 2, 2025).