BC Conservation Data Centre: Conservation Status Report
Marah oregana
coast manroot
| Scientific Name: | Marah oregana |
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| Scientific Name Synonyms: |
Marah oreganus
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| English Name: | coast manroot |
| Provincial Status Summary | |
| Status: | S1 |
| Date Status Assigned: | February 20, 2003 |
| Date Last Reviewed: | April 30, 2019 |
| Reasons: | There are a total of 18 individual plants of Marah oreganus in three locations, over 3050 square metres. A fourth population has been extirpated. Each population exists in a landscape highly fragmented by residential and recreational development. Suitable habitat is declining in both area and quality. The largely discontinuous areas of suitable shoreline habitat increases the dependence of this species on relatively rare events of long-distance dispersal across hostile habitats such as roads and farmland. Plants would have to become established in sites where many of the open areas have been colonized by aggressive weedy exotics. Forest succession on similar sites in the surrounding landscape may also limit establishment and survival. Due to their small size, existing populations are vulnerable to demographic and environmental variation and loss of genetic variability. |
| Range | |
| Range Extent: | A = <100 square km |
| Range Extent Comments: | Populations are restricted to a small area of southeastern Vancouver Island and the southern Gulf Islands. The contemporary extent of occurrence is estimated at less than 37 square kilometres. Its historical range is difficult to determine because information on its occurrence is not found in the literature or in collections, prior to 1958. |
| Area of Occupancy (km2): | AC = 1-5 |
| Area of Occupancy Comments: | The total area of occupancy is currently 3050 square metres. Marah oreganus was probably never common in British Columbia given that the species it is at the northern edge of its range and because of its low colonization rate. |
| Occurrences & Population | |
| Number of Occurrences: | A = 1 - 5 |
| Comments: | There are 3 known occurrences for this species. The population at a fourth location on South Pender Island is considered extirpated as no plants have been observed since 1964. |
| Number of Occurrences with Good Viability / Ecological Integrity: | B = 1 - 3 |
| Comments: | Two occurrences (EO #2, 6) are assessed as having good viability. |
| Number of Occurrences Appropriately Protected & Managed: | A = None |
| Comments: | None of the known extant populations are protected. |
| Population Size: | A = 1 - 50 individuals |
| Comments: | In 2006, the Canadian population consisted of 18 mature individuals at three locations. |
| Threats (to population, occurrences, or area affected) | |
| Degree of Threat: | Unknown |
| Comments: | Threats to Marah oreganus include habitat loss due to residential and recreational development, grazing, invasive alien species and altered hydrological regimes. The largely discontinuous areas of suitable shoreline habitat, increases the dependence of this species on relatively rare events of long-distance dispersal across hostile habitats such as roads and farmland. Plants would have to become established in sites where many of the open areas have been colonized by aggressive weedy exotics that compete for rooting space, moisture and nutrients. Forest succession on similar sites in the surrounding landscape may also limit establishment and survival. The plant does not appear to be eaten by domestic livestock, but the single plant on South Pender Island, last observed in 1964, was likely destroyed by trampling. However, it is also possible that its disappearance may not have been a consequence of direct browsing or trampling of the plant itself, but rather to the increased compaction and subsequent water logging of soils caused by trampling. Chemical pesticides or herbicides may harm or kill the plant or its pollinators. |
| Trend (in population, range, area occupied, and/or condition of occurrences) | |
| Short-Term Trend: | F = Decline of 10-30% |
| Comments: | The population at South Pender Island has not been observed since 1964 and is considered extirpated, representing a 25 percent decline in the total number of populations. The habitat at each known site appears to be relatively stable over the short-term, but this needs to be confirmed with site monitoring. |
| Long-Term Trend: | BC = Decline of 70-90% |
| Comments: | The amount of potential habitat has declined greatly over the past century as coastal areas in southeast Vancouver Island have been developed for residential and recreational uses. In the Victoria area, Garry oak ecosystems have declined to less than 5% of their original extent (Lea 2006) and this trend also likely corresponds to the decline in suitable habitat for Marah oreganus. Most of the remaining habitat has been heavily altered by the abundance of invasive exotics including shrubs, graminoids and forbs. Plants have been observed at the Union Bay site since 1898, but information on the number and the size of plants is lacking from collection labels. Since the longevity of a single plant is unknown, long-term population trends could not be determined |
| Other Factors | |
| Intrinsic Vulnerability: | C=Not intrinsically vulnerable |
| Comments: |
Once it is well established, this species appears to tolerate some disturbance. The population at Union Bay grows in non-native vegetation along a weedy roadside that is mowed irregularly by highway crews. Portions of the vine at this site have been cut back by mechanical brush control, yet the plant continues to flower and produce fruit. Since each root has many buds capable of producing new plants, it is possible that a plant can survive mechanical disturbance such as mowing or grazing, once it has accumulated a sufficient amount of food reserves in the root. However, current populations seem to persist for years without establishing new plants from seeds and the low abundance and low colonization rate suggests that there are other factors (e.g. microclimatic, self-incompatibility) that limit the successful establishment and persistence of this species in British Columbia. Interspecific competition for rooting space, soil moisture and nutrients from invading trees and shrubs (especially Cytisus scoparius) may be limiting and present conditions inimical to germination and survival. |
| Environmental Specificity: | C=Moderate. Generalist or community with some key requirements scarce. |
| Comments: |
The extant and historic populations occur on south-facing, rocky hillsides, in soil pockets amongst outcropping rock and in openings at the margins of mixed woodlands, at low elevations near the coast, often within 30 metres of the water's edge. The extirpated population on South Pender Island occurred in a cleared pasture, along the margin of a second-growth forest that is now dominated by dense, young forest. By decreasing the amount of exposed mineral soil or by competing for moisture during critical times of the growing season, the changes to species composition and community structure at this site could present conditions inimical to the germination and establishment of Marah oreganus. |
| Other Rank Considerations: | |
| Information Gaps | |
| Research Needs: | More research is needed to more fully understand the germination and ecological requirements for this species in British Columbia. In addition, genetic studies could identify if the peripheral populations in B.C. are divergent from populations in the central parts of its range. |
| Inventory Needs: | Suitable growing sites have been surveyed repeatedly since the early 1980s in a variety of projects designed to document the distribution of rare plants in open meadows and coastal bluffs in southeast Vancouver Island and the Gulf Islands. The principal surveyors include botanists who are familiar with Marah oreganus such as Hans Roemer, Matt Fairbarns, Frank Lomer and Harvey Janszen, who has completed boat surveys of the southern Gulf Islands, but many other botanists have searched these areas without having reported this striking plant. |
| Stewardship | |
| Protection: | As many populations as possible should be protected. Since all populations occur on private property, this could involve the creation of conservation covenants. |
| Management: | |
| Version | |
| Author: | Donovan, M. |
| Date: | October 16, 2007 |
| References | |
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COSEWIC. 2009. COSEWIC assessment and status report on the Coast Manroot Marah oreganus in
Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 28 pp. (www.sararegistry.gc.ca/status/status_e.cfm). |
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Donovan, M. and M. Fairbarns. 2007. Draft COSEWIC Status Report on Coast Manroot Marah oreganus. Prepared for the Comm. on the Status of Endangered Wildl. in Can. 20pp.
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Douglas, G.W., D. Meidinger, and J. Penny. 2002. Rare Native Vascular Plants of British Columbia, 2nd ed. B.C. Conserv. Data Centre, Terrestrial Inf. Branch, Victoria. 358pp.
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Lea, T. 2006. Historical Garry Oak Ecosystems of Vancouver Island, British Columbia, pre-European Contact to the Present. Davidsonia 17(2):34-50. http://www.davidsonia.org/bc_garryoak
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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. 2007. Conservation Status Report: Marah oregana. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Apr 20, 2024).