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BC Conservation Data Centre: Conservation Status Report

Camissonia contorta
contorted-pod evening-primrose


 
Scientific Name: Camissonia contorta
Scientific Name Synonyms: Oenothera cruciata
English Name: contorted-pod evening-primrose
   
Provincial Status Summary
Status: S1
Date Status Assigned: April 30, 1996
Date Last Reviewed: April 30, 2019
Reasons: Camissonia contorta is an annual herb with high habitat specificity, restricted to several dry, open and sandy coastal habitats of very small size. The small, fragmented and possibly declining populations are impacted by ongoing habitat loss, high recreational use and competition from invasive exotic plants. The plants have poor dispersal/recovery capabilities and several populations may be at risk of demographic collapse due to small population size.
 
Range
Range Extent: D = 1,000-5,000 square km
Range Extent Comments: The range extent is estimated at 2,843 square kilometres.  Six of the eight known extant populations occur in the Victoria area. The other two populations occur in close proximity on Savary Island, approximately 178 km to the northwest. However, much of the area between these known populations represents unsuitable habitat (rocky, forested or developed coastline, open water). Suitable habitat of open, sandy areas along the coast are scattered and small.
Area of Occupancy (km2): D = 6-25
Area of Occupancy Comments: The estimated area of occupancy is 28 square kilometres or 7 - 4 square kilometre grid cells. 
 
Occurrences & Population
Number of Occurrences: B = 6 - 20
Comments: There are six extant populations in BC, one of which re-appeared at the East Saanich IR in 2007 after being considered extirpated in 2004 (M. Fairbarns, pers. comm. 2007).
Number of Occurrences with Good Viability / Ecological Integrity: B = 1 - 3
Comments: Viability of populations is difficult to determine because of the lack of data needed to determine population trends. Populations are generally small, disjunct, and prone to potential threats such as trampling, invasive species (Cytisus scoparius), or catastrophic events, both natural and anthropogenic.
Number of Occurrences Appropriately Protected & Managed: B = 1 - 3
Comments: The smallest population, comprised of approximately 20 individuals in 1 square metre, is located in a National Park, but encroachment by Cytisus scoparius (and probable extirpation) seems imminent (COSEWIC 2006c). Two other populations are within the Capital Regional District parks. These populations are protected under park policy (protection of rare, threatened, and endangered plants), but a high level of recreational activity in the parks may negate the effects of these policies.
Population Size: E = 2,500 - 10,000 individuals
Comments: The estimated population size is 3700-4750 mature plants (COSEWIC 2006c; M. Fairbarns, pers. comm. 2007). Individual populations range in size from 20 to 2000 individuals. The number of populations comprising a specific range of numbers of individuals are as follows: 0-100 individuals (2 populations), 100-500 individuals (3 populations), 500-1000 individuals (2 populations), > 1000 individuals (1 population).
 
Threats (to population, occurrences, or area affected)
Degree of Threat: Substantial, imminent threat
Comments: The COSEWIC status report (2006c) identifies five major threats:
(1) habitat loss and altered sand dynamics: the introduction of breakwaters, retaining walls, and other shoreline armouring features have eradicated sandy backshore areas;
(2) recreational activities (walking, sunbathing, bicycling, walking dogs, motorized vehicle use) have great potential to destroy populations. A population in Saanich was extirpated as a direct result of four-wheel-drive activity;
(3) invasive plants: Cytisus scoparius is the greatest threat because it overtakes and shades out smaller species in Camissonia contorta habitat. Some grasses (Bromus spp. and Aira ssp.) and forbs (Rumex acetosella) are aggressive colonizers of C. contorta habitats and may set the stage for the establishment of secondary colonizers and subsequent site succession to a closed vegetation structure. Two other potentially problematic plants are Allium vineale and Ammophila arenaria. The coalescing of substrate particles (sand) from dense vegetation cover will inhibit the establishment of Camissonia contorta;
(4) the small population sizes (less than 1000 plants in 7 of the 8 extant sites) suggest the populations are prone to "demographic collapse". They are also very vulnerable to environmental stochasticity and potential catastrophic events; and
(5) herbivory by eastern cottontails (Sylvilagus floridanus) was observed at two populations in the Victoria area but is not considered to be a significant threat. The impact of grazing on competing vegetation appears to outweigh the minor impact on Camissonia contorta.
 
Trend (in population, range, area occupied, and/or condition of occurrences)
Short-Term Trend: E = Decline of 30-50%
Comments: One population has recently re-appeared after not being seen for two years, and another has declined by 95 percent. Overall, the Canadian population of Camissonia contorta has declined by an estimated 30-35 percent in recent years (COSEWIC 2006c).
Long-Term Trend: U = Unknown
Comments: The COSEWIC status report (2006c) suggests that the long-term trend is a decline in area of occupancy, extent and quality of habitat, and total population. Insufficient data are available to accurately determine the magnitude of the trend, but Camissonia contorta populations may have experienced a substantial decline (C) due to human affinity for and occupancy of sites required by this species (sandy, oceanside sites).
 
Other Factors
Intrinsic Vulnerability: A=Highly vulnerable
Comments: Populations are small and restricted to very specific habitats which are uncommon and subject to various threats.
Environmental Specificity: A=Very narrow. Specialist or community with key requirements scarce.
Comments: The species is restricted to low-lying, seaside, sandy backshore sites.
Other Rank Considerations:
 
Information Gaps
Research Needs: Reproduction dynamics of British Columbia populations are poorly understood. Subjects that require investigation include dispersal ability and mechanisms (wind, animals, etc.), substrate dynamics (effects of substrate and its movement, etc., on reproductive success), and pollination by insects. Studies are also required to determine by what means and to what degree certain types of disturbance (natural and anthropogenic) affect populations. This could include the effects of invasive plant species. Additionally, population trends need to be investigated, and the sustaining characteristics of these populations need to be identified. This addresses the issue of demographic collapse. At what level (number) are populations considered to be self-sustaining and how do different substrates and conditions affect population viability?
Inventory Needs: Immediate surveys of extant populations are not required, although an inventory monitoring program should be established so that population trends can be determined. The smallest, most vulnerable populations should be monitored diligently to determine status and prevent extirpation. Reports of potential new sites should be documented for future investigation, and surveys of suitable habitat should be completed opportunistically.
 
Stewardship
Protection: All populations need some level of protection (from gross disturbances) and may require protection from invasive species (especially Cytisus scoparius). Site monitoring will help determine protection needs. Small, concentrated populations are very susceptible to disturbance and eradication and should receive immediate attention. The smallest population of 20 individuals in 1 m2 should be monitored diligently and supported with whatever actions are deemed necessary. These may include exclosures (to humans and small mammals) and the removal of invasives or substrate-binding/covering plants that may impede reproduction, dispersal, and persistence.
Management: Existing populations need to be secured. The immediate need is to prohibit major disturbances that will lead to the probable eradication of the population. This includes major developments (buildings, roads, trails, recreational features). Population monitoring is needed to determine population trends and the levels and types of disturbance that are affecting the populations. This will inform additional management needs.
 
Version
Author: Henderson, P., S. Hartwell and M. Donovan
Date: April 29, 2015
 
References
COSEWIC. 2006c. COSEWIC assessment and status report on the contorted-pod evening-primrose Camissonia contorta in Canada. Comm. on the Status of Endangered Wildl. in Can. Ottawa. vi + 21 pp.
Fairbarns, M. 2004d. Potential recovery actions for Contorted-pod Evening-primrose in CRD Parks: report prepared for CRD Parks by Aruncus Consulting. 14 pp. + append.
 

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Suggested Citation:

B.C. Conservation Data Centre. 2015. Conservation Status Report: Camissonia contorta. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Apr 14, 2021).