Coastal Manroot Marah oregana: COSEWIC rapid review of classification 2022

Official title: COSEWIC Rapid Review of Classification on the Coastal Manroot Marah oregana in Canada

Endangered

2022

COSEWIC assessment summary

Assessment summary – December 2022

Common name: Coastal Manroot

Scientific name: Marah oregana

Status: Endangered

Reason for designation: This long–lived perennial vine occurs in Canada at only four widely separated subpopulations on southeastern Vancouver Island and adjacent Gulf Islands. Fewer than 50 mature plants remain, with evidence of seedling production at only one site. Losses of habitat, subpopulations, and mature individuals are projected in its Canadian range. Main threats are development of the few known sites, alien species, and random events affecting the handful of remaining individuals. This is a medicinal plant cared for by some west coast First Nations.

Occurrence: British Columbia

Status history: Designated Endangered in November 2009. Status re-examined and confirmed in December 2022.

COSEWIC rapid review of classification

Preface

Coastal Manroot (Marah oregana) (Nesom 2015) was formerly called “Coast Manroot” (Marah oreganum) in the previous assessment (COSEWIC 2009). A single new (previously overlooked) occurrence at Thetis Island and a few additional individuals of Coastal Manroot have been found since the last COSEWIC assessment. This increases the EOO by 23%, the IAO slightly and the number of mature individuals by 30%–90%. The distribution of the species (Figure 1) remains the same as described in the Recovery Strategy (BC Ministry of Environment 2012).

Although not emphasized in COSEWIC (2009), it is possible that not all the subpopulations have dispersed into Canada naturally. The first collection of the plant from Union Bay Indian Reserve No. 1, noted that it occurred in “Indian villages and gardens.” The fruit had medicinal uses among the Washington Salish (Turner and Bell 1971). Turner and Bell (1971) suggested it was planted, and Ms. Melburn, a collector in 1958, noted “escaped from cultivation” on her collection label. However, while the current plants are not obviously connected to cultivated areas, some do occur in disturbed sites. The other subpopulations are not obviously linked to sites with Indigenous cultivation. The Kwixin Field Station (2018) characterizes the management by one W̱SÁNEĆ community of the Saanich and Salt Spring occurrences as “stewardship.” All sites where the species occurs with no direct evidence of cultivation have been treated as native in this report. Two individual plants, one in a private garden in Victoria and another in a public garden in Saanich were not included in this assessment.

Exact counts of mature individuals have not been possible for two reasons:

• there are new and known sites on private lands and access and permission has not been obtained from landowners to gather^{Footnote 1}or release these data
• some visits have not occurred at the correct time of year to determine whether the plants were flowering or fruiting. BC MOE (2012) notes that a very small number of stems are known to produce flowers or fruit and the total number of plants tallied may be higher than the number of mature individuals

However, even with these caveats, the number of mature individuals in Canada is estimated to be below 50 (Donovan pers. comm. 2021) and possibly much lower if stems that are not fruiting are removed from this estimate. The range of mature individuals used in this reassessment is 24 to 34.

Some of the subpopulations are in maturing forests and may no longer receive enough light to reproduce properly (Fraser pers. obs.).

Coastal Manroot is not listed in the Canadian Species at Risk Act, nor is it protected in legislation in British Columbia. No occurrences are in protected areas and all are on First Nations or private lands.

Indigenous traditional knowledge: The Saanich plant and the subpopulation on Salt Spring Island are stewarded by the W̱SÁNEĆ community as a medicinal plant (ḴEXMIN Field Station 2018).

Status history

Designated Endangered in November 2009. Status re-examined and confirmed in December 2022.

Updated map

Technical summary

Marah oregana

Coastal Manroot

Marah d’Orégon

Range of occurrence in Canada: British Columbia

Extent and occupancy information

Estimated extent of occurrence (EOO)

330 km²

Index of area of occupancy (IAO) (Always report 2x2 grid value).

16 km²

Is the population severely fragmented i.e., is >50% of its total area of occupancy in habitat patches that are (a) smaller than would be required to support a viable population, and (b) separated from other habitat patches by a distance larger than the species can be expected to disperse?

Probably. Seeds in USA are dispersed by rodents and freshwater movement. All subpopulations are very small and may not be viable in the longer term.

Number of locations (use plausible range to reflect uncertainty if appropriate)^*:

Saanich Peninsula Union Bay Indian Reserve 1
North Pender Island 1
Salt Spring Island (undisclosed location) 1 landowner
Thetis Island (undisclosed location) 2 landowners

Most plausible threats vary by landowners.

5

Is there an [observed, inferred, or projected] decline in extent of occurrence?

Possible, since the loss of any one site due to development or shading (seedlings) would reduce EOO. The increase in reported EOO from the previous status report is from new sites being recorded, not an actual increase in the range of the species..

Is there an [observed, inferred, or projected] decline in index of area of occupancy?

Possible

Is there an [observed, inferred, or projected] decline in number of subpopulations?

Yes, observed. One subpopulation was lost on South Pender Island (1960s)

Is there an [observed, inferred, or projected] decline in number of "locations"^*?

Yes, observed. One subpopulation was lost on South Pender Island (1960s)

Is there an [observed, inferred, or projected] decline in [area, extent and/or quality] of habitat?

Yes, decline in quantity and quality of habitat due to threats and recent land clearing at one site

Are there extreme fluctuations in number of subpopulations?

No

Are there extreme fluctuations in number of "locations"^*?

No

Are there extreme fluctuations in extent of occurrence?

No

Are there extreme fluctuations in index of area of occupancy?

No

^* See COSEWIC definitions and abbreviations on website for more information on this term.

Number of mature individuals (in each subpopulation)

Subpopulations (give plausible ranges) totals:

Saanich Peninsula, Patricia Bay, Tseycum First Nation, Union Bay IR4: 1– 2^*

South Pender Island: Presumed extirpated

North Pender Island: 2

Salt Spring Island (undisclosed locality): Estimated (6–15)

Thetis Island (undisclosed locality): Estimated (15)

Number mature individuals total: 24–34

^*range reflects uncertainty in counts and numbers of plants that are actually capable of reproduction

Quantitative analysis

Is the probability of extinction in the wild at least [20% within 20 years or 5 generations whichever is longer up to a maximum of 100 years, or 10% within 100 years]?

Not done.

Threats (direct, from highest impact to least, as per IUCN Threats Calculator)

Was a threats calculator completed for this species?

A threats calculator was developed for the recovery plan (BC MOE 2012). Overall threat impact was not reported in the recovery plan but one Medium and four Low, Level 1 threats would result in an overall High threat impact. The following are the Threats Category numbers, and name and impact scores.

1. Residential and Commercial Development: Medium impact
1.1 Housing and Urban Areas: Medium impact

4. Transportation and Service Corridors: Low impact
4.1 Roads and Railways: Low impact

6. Human Intrusions and Disturbance: Low impact
6.1 Recreational Activities: Low/Negligible impact (trampling)?

7. Natural System Modifications: Low impact
7.1 Fire and Fire Suppression: Low/Negligible impact
7.3 Other Ecosystem Modifications: Low impact

8. Invasive and Other Problematic Species and Genes: Low impact
8.1 Invasive Non-native/Alien Species: Low impact

What additional limiting factors are relevant?

• Manroot may be self-incompatible (Schlising 1966 cited in BC MOE 2012) and subpopulations with single individuals may not count as “mature individuals” if pollinator dispersal distances from other plants are exceeded.
• The species is very long-lived and seedling recruitment may be low. Only the Thetis Island site appears to have seedling recruitment (Donovan pers. comm. 2021).

Rescue effect (immigration from outside Canada)

Status of outside population(s) most likely to provide immigrants to Canada.

Extant, but uncommon in the San Juan Islands of Washington State. Seeds are large and heavy and thought to be mostly animal-dispersed.

Is immigration known or possible?

Unlikely, because the seeds would need to disperse from island to island and most seed dispersal is done by rodents.

Would immigrants be adapted to survive in Canada?

Yes

Is there sufficient habitat for immigrants in Canada?

Possibly, but alien plants are present in much of the suitable habitat

Are conditions deteriorating in Canada?⁺

Yes

Are conditions for the source (i.e., outside) population deteriorating?⁺

Yes, similar suite of alien species in the San Juan Islands of Washington State

Is the Canadian population considered to be a sink?⁺

No

Is rescue from outside populations likely?

Unlikely

⁺See Table 3 (Guidelines for modifying status assessment based on rescue effect).

Data sensitive species

Is this a data sensitive species?

No, but all occurrences take place on Indigenous or private lands.

Status and reasons for designation

Status: Endangered

Alpha-numeric codes: B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v); C2a(i); D1

Reasons for designation: This long–lived perennial vine occurs in Canada at only four widely separated subpopulations on southeastern Vancouver Island and adjacent Gulf Islands. Fewer than 50 mature plants remain, with evidence of seedling production at only one site. Losses of habitat, subpopulations, and mature individuals are projected in its Canadian range. Main threats are development of the few known sites, alien species, and random events affecting the handful of remaining individuals. This is a medicinal plant cared for by some west coast First Nations.

Applicability of criteria

Criterion A (Decline in total number of mature individuals): Not applicable. Decline insufficient to meet threshold.

Criterion B (Small distribution range and decline or fluctuation):

Meets Endangered, B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v). EOO (330 km²) and IAO (16 km²) are both below thresholds for Endangered. The species is known from 5 locations (landowners) and there is a continuing observed and inferred decline in the quality of the habitat, inferred decline in EOO, IAO, observed decline in locations and number of subpopulations, and observed and inferred decline in number of mature individuals.

Criterion C (Small and declining number of mature individuals):

Meets Endangered, C2a(i). There has been an observed decline in mature individuals in the past, and threats are ongoing that could qualify for “continuing decline.” No subpopulation is larger than 50 individuals.

Criterion D (Very small or restricted population):

Meets Endangered, D1. Population estimate is fewer than 50 individuals, far below the threshold of 250 mature individuals.

Criterion E (Quantitative analysis):

Not applicable. Analysis not conducted.

Acknowledgements

Sincere thanks are extended to all the authorities contacted (below) for the information and discussion of the current status of Coastal Manroot. Leah Ramsay and Jenifer Penny (BC CDC) provided useful comments on an early draft of this RRoC. Katrina Stipec (BC CDC) updated the values for the IAO and EOO. Marta Donovan (BC CDC) provided information on recent surveys on Thetis Island and provided useful comments on an earlier draft. Brenda Costanzo (BC Ministry of Environment and Climate Change) provided recent observations of the Saanich Peninsula population.

Authorities contacted

• Brenda Costanzo, Vegetation Specialist, BC Ministry of Environment and Climate Change, Victoria.
• Jenifer Penny, Botanist, BC Conservation Data Centre, Victoria.
• Katrina Stipec, Data Specialist, BC Conservation Data Centre, Victoria.
• Marta Donovan, Botanist. BC Conservation Data Centre, Victoria.

Information sources

BC Conservation Data Centre. 2019. Conservation Status Report: Marah oregana, coast manroot. Victoria, British Columbia. Website: https://a100.gov.bc.ca/pub/eswp/esr.do?id=19892 [accessed February 2021].

BC Ministry of Environment. 2012. Recovery Plan for Manroot (Marah oreganus) in British Columbia. Victoria, British Columbia. 17 pp. Website: http://a100.gov.bc.ca/pub/eirs/finishDownloadDocument.do?subdocumentId=9153 [accessed February 2021].

COSEWIC 2009. Coast Manroot (Marah oregana): COSEWIC assessment and status report. Ottawa, Ontario. Website: https://www.canada.ca/en/environment-climate-change/services/species-risk-public-registry/cosewic-assessments-status-reports/coast-manroot-2009.html#_Toc252872951 [accessed January 2021].

Costanzo, B., pers. comm. 2021. Email correspondence to David Fraser. June 2021. BC Ministry of Environment and Climate Change, Victoria, British Columbia.

Donovan, M., pers. comm. 2021. Email correspondence to David Fraser. August 2021. BC Conservation Data Centre and Climate Change, Victoria, British Columbia.

ḴEXMIN Field Station, 2018. Immature fruit of coastal manroot, Marah oregana: traditionally stewarded and used by some Salish communities. Website: http://gordonbrentingram.ca/KEXMINfieldstation/2018/06/08/.

Nesom, G.L. 2015. Cucurbitaceae Jussieu, Cucumber Family in: Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico [Online]. 22+ vols. New York and Oxford. Vol. 6. Website: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=10233 [accessed September 2022].

Schlising, R.A. 1966. Reproductive ecology of plants in the genus Marah (Cucurbitaceae). Ph.D. dissertation, University of California, Berkeley, California. 179 pp.

Turner, N.C., and M.A.M. Bell. 1971. The ethnobotany of the Coast Salish Indians of Vancouver Island. Economic Botany 25:63–99. Website: https://doi.org/10.1007/BF02894564 [accessed February 2021].

Writer of rapid review of classification:

• David F. Fraser

COSEWIC history

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

Definitions (2022)

Wildlife Species

A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.

Extinct (X)

A wildlife species that no longer exists.

Extirpated (XT)

A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)

A wildlife species facing imminent extirpation or extinction.

Threatened (T)

A wildlife species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)*

A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.

Not at Risk (NAR)**

A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data Deficient (DD)***

A category that applies when the available information is insufficient (a) to resolve a species’ eligibility for assessment or (b) to permit an assessment of the species’ risk of extinction.

* Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990.

** Formerly described as “Not In Any Category”, or “No Designation Required.”

*** Formerly described as “Indeterminate” from 1994 to 1999 or “ISIBD” (insufficient scientific information on which to base a designation) prior to 1994. Definition of the (DD) category revised in 2006.

The Canadian Wildlife Service, Environment and Climate Change Canada, provides full administrative and financial support to the COSEWIC Secretariat.