Silver hair moss (Fabronia pusilla) COSEWIC assessment and status report: chapter 2

COSEWIC Executive Summary

Silver hair moss
Fabronia pusilla

Species information

Fabronia pusilla, the silver hair moss, is a tiny, creeping moss characterized by small leaves that are bordered by cilia-like and often multi-cellular teeth along the margins. Long, clear awns, or leaf tips, are also characteristic of this species. Occasionally, it has been considered a synonym of F. ciliaris, but the often multi-cellular, cilia-like teeth along the leaf margins separate F. pusilla from this species.

Distribution

Globally, this species has a western North American – western Europe/North African distribution, principally in Mediterranean-type climates. In Canada, it has been found at only two sites: on Sumas Mountain east of Abbotsford, and near Lower Arrow Lake in the Kootenay Valley. The Arrow Lake site is now submerged behind a dam, and it has not been collected from the area since the late 1800s. The Canadian populations appear to be at the northern limit of the distribution of this species, which is more widespread and common southwards.

Habitat

In British Columbia, Fabronia pusilla has been found only on rock faces and in crevices. Elsewhere, it has been found in seasonally dry habitats on rock and trees. The British Columbia habitat appears stable.

Biology

It is a perennial, creeping moss that grows on semi-exposed rock or bark substrata. It is an autoicous moss that produces sporophytes frequently across its range. Both of the Sumas Mountain collections have sporophytes.

Population sizes and trends

It was not found during the present work, and no detailed information on its population was gathered when it was first collected in 1968.

Limiting factors and threats

Competition with associated larger moss species, forest fire, and rock face degradation are potential, but probably minor, threats.

Special significance of the species

Fabronia pusilla is relatively widespread in the southern portions of its range in North America, but becomes less common northward, and is rare in southern British Columbia.

Existing protection or other status designations

No legislation, regulations, customs, or conditions exist to protect Canadian populations of Fabronia pusilla. Globally this species is tentatively considered common to very common (G5?). F. pusilla is Red-listed (S1) in British Columbia and listed S1 in Oregon.

Summary of the status report

The single Canadian site for Fabronia pusilla was intensively surveyed in 2001, but the species was not re-located. While it is possible that the Fabronia pusilla is still extant at the site because of the extensive area of suitable habitat, the species’ small size and gregarious nature make it difficult to find in the field. These factors may also account for the species’ apparent rarity in Canada.

COSEWIC Mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) determines the national status of wild species, subspecies, varieties, and nationally significant populations that are considered to be at risk in Canada. Designations are made on all native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fish, lepidopterans, molluscs, vascular plants, lichens, and mosses.

COSEWIC Membership

COSEWIC comprises representatives 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 Biosystematic Partnership), three nonjurisdictional members and the co-chairs of the species specialist groups. The committee meets to consider status reports on candidate species.

Definitions

Species
Any indigenous species, subspecies, variety, or geographically defined population of wild fauna and flora.

Extinct (X)
A species that no longer exists.

Extirpated (XT)
A species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)
A species facing imminent extirpation or extinction.

Threatened (T)
A species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)Footnote1
A species of special concern because of characteristics that make it particularly sensitive to human activities or natural events.

Not at Risk (NAR)Footnote2
A species that has been evaluated and found to be not at risk.

Data Deficient (DD)Footnote3
A species for which there is insufficient scientific information to support status designation.

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.

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

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