Mountain holly fern (Polystichum scopulinum) COSEWIC assessment and status report: chapter 2

COSEWIC Executive Summary

Mountain Holly Fern
Polystichum scopulinum

Species information

Polystichum scopulinum is an evergreen, perennial, tufted fern arising from a short, stout rhizome. The ascending leaves (fronds) are 10-50 cm long, 3-7 cm wide and 1-pinnate. The 20-40 leaflets (pinnae) on each side of the rachis are oblong with acute leaflet divisions (pinnules) and have ultimate segments that are minutely, spiny-toothed. The round spore dots (sori) are attached near the midvein and covered with entire or fringed flaps of tissue (indusia).

Distribution

Polystichum scopulinum ranges from southwestern British Columbia, sporadically south in the western United States to Colorado, Arizona and California. It is also disjunct to northeastern Quebec and western Newfoundland. In British Columbia it is known from the Tulameen River valley, northwest of Princeton in southwestern British Columbia. In Quebec, it is known from Mont Albert on the Gaspé Peninsula. The status of a historic population known from a 1950 collection from Humber West (North Arm) in western Newfoundland is still unknown in spite of recent limited searches.

Habitat

In North America, P. scopulinum is restricted to sites with ferromagnesian or ultramafic (serpentine) rock outcrops. Although a number of ultramafic rock outcrops occur in western British Columbia, only the ultramafic (olivine clinopyroxenite) band (at elevations of 978 to 1768 m) between Olivine Mountain and Grasshopper Mountain in the Tulameen River valley supports the species. These slopes have a typically depauperate ultramafic flora and tree cover. This is in contrast to the dense surrounding montane forests dominated by Douglas-fir (Pseudotsuga menziesii). In Quebec, P. scopulinum is restricted to the southerly slopes of the Vallée du Diable, on the eastern flank of Mount Albert, at an elevation of 800 to 900 m. The flora is similarly depauperate and includes local serpentine endemics like Minuartia marcescens, Salix chlorolepis and Solidago simplex subsp. simplex var. chlorolepis. The species occurrence in Newfoundland was reported from southerly slopes of a dry serpentine ridge.

Biology

There is only limited information on biology and ecology of P. scopulinum. Plants occurring on ultramafic habitats are adapted to tolerate low levels of calcium, nitrogen, phosphorus and molybdenum and high levels of magnesium, chromium and nickel. These rock outcrop habitats are also characterized by shallow soils and a sparse groundcover thus creating xeric microclimates that also exclude many nearby species adapted to more mesic microclimates.

Population sizes and trends

The three recorded populations of P. scopulinum in British Columbia occur on a 100 m by 4 km band of ultramafic rock outcrop that extends from Olivine Mountain on the south side of the Tulameen River to Grasshopper Mountain on the north side of the Tulameen River. Population numbers range from five to 400 plants. It is quite likely that a number of other populations occur on the ultramafic band, but the rugged terrain makes access extremely difficult. The population of P. scopulinum in BC has remained stable between 1996 and 2002. The single Quebec population consists of nine small colonies in close proximity, with a total of about 215 individuals. No demographic data are available for a Newfoundland population last seen in 1950. Due to its relatively remote location, perennial nature, and asexual reproduction by spreading rhizomes the population may still be extant.

Limiting factors and threats

The most direct threat to Polystichum scopulinum in British Columbia at the present time is from mining exploration, road construction or forest fires. In Quebec, it is suspected that over-collecting has significantly reduced the population in the first half of the 20th century; no such threat exists presently. Due to the ultramafic properties of the soils at all sites, introduced species are of no concern. Threats, if any, cannot be determined at present for the historic Newfoundland population.

Special significance of the species

Polystichum scopulinum belongs to a relatively small group of species with a restricted Pacific Coast range that have their northern limits in southwestern British Columbia. In Quebec the species is even more dramatically disjunct. The importance of these peripheral and disjunct populations, especially with respect to their genetic characteristics, has yet to be studied adequately. Peripheral populations are often genetically and morphologically divergent from central populations and may have an evolutionary and ecological significance out of proportion to the percentage of the species they represent. The protection of genetically distinct peripheral populations may be important for the long-term survival of the species as a whole.

Existing protection or other status designations

The British Columbia Conservation Data Centre has ranked this species as S1 and is on the provincial Ministry of Sustainable Resource Management red list. This is the most critical category for imperiled rare native vascular plants in the province. In Quebec it is also ranked S1 by the Centre de données sur le patrimoine naturel du Québec, Ministère de l'Environnement du Québec.A rank of S1 is considered “critically imperiled because of extreme rarity (5 or fewer occurrences or very few remaining individuals) or because of some factors making it especially vulnerable to extirpation or extinction.” Globally, P.scopulinum is ranked G5 and is frequent to common in the core of its range.

There is no specific legislation for the protection of rare and endangered vascular plants in British Columbia. The population in the Tulameen River area of British Columbia is on public land but is not part of a protected area. It is conceivable that this area could qualify as an ecological reserve but this status has yet to be proposed. In Quebec, P scopulinum is located in a provincial park (Parc de la Gaspésie). The species was designated "Threatened" by the Quebec government in 1993, and its habitat is legally protected. In Newfoundland, the species is ranked as SH by NatureServe and “May Be At Risk” by the province.

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 agencies (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 members and the co-chairs of the species specialist and the Aboriginal Traditional Knowledge subcommittees. The Committee meets to consider status reports on candidate species.

Definitions (November 2004)

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

Data Deficient (DD)Footnotec
A wildlife species for which there is inadequate information to make a direct, or indirect, assessment of its risk of extinction.

 

Canadian Wildlife Service

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

 

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