Blunt-lobed woodsia (Woodsia obtusa) COSEWIC assessment and status report: chapter 2

• Previous page
• Table of contents
• Next page

COSEWIC Executive Summary

Species information

Blunt-lobed woodsia (Woodsia obtusa) is a small to medium-sized fern characterized by the blunt, rounded lobes of its fronds. The leaf stalk (rachis) is straw-coloured, occasionally darker at base and relatively brittle. The blade is coarsely cut and twice divided (2-pinnate), typically composed of 8-17 pairs of leaflets (pinnae). Two chromosomal variants are known and are treated as subspecies; the one found in Canada is Woodsia obtusa subsp. obtusa.

Distribution

Blunt-lobed woodsia is a widespread and common species in the eastern United States; in Canada, it is known from only nine populations in Ontario and Quebec, all located within 100 km of the US border. In Ontario, populations are concentrated along the Frontenac Axis. In Quebec, two distinct regions contain populations, one located in Gatineau Park and the other in Missisquoi County. Plants are also cultivated and available from nurseries.

Habitat

All Canadian populations are found in the Great Lakes-St.Lawrence Forest Region and all are located on calcareous rock with a southern aspect. The habitat of the species is generally forested, with an average canopy closure of 82%. A recent study on six Canadian sites shows an average soil depth of 3.5 cm on an average slope of 43°. No sites appear to have been drastically modified over the recent years. Most sites are located within abandoned or rarely used areas that are not likely to suffer from direct human disturbance.

Biology

Blunt-lobed woodsia is a perennial, homosporous fern (spores producing male and female gametophytes are identical in size and form) that produces high numbers of spores annually towards the end of summer and beginning of fall. These develop into haploid gametophytes (sex cell producing plantlets). The species is not known to reproduce vegetatively, although bisexual gametophytes can be produced and self fertilize, resulting in completely homozygous individuals.

Population sizes and trends

There are currently four known sites in Ontario, of which only two were mentioned in the original status report. Two more have since been added, one of which was rediscovered in 2001 after initially being found in 1978; the other was found in 2004. All were visited in 2005. Of the five known Quebec populations, one (Champlain Lookout, Gatineau Park) has not been located despite several attempts and is likely extirpated, and two could not be visited due to refusal of access or inability to contact the landowner. The others were visited in 2005. Generally, numbers have increased at sites; however, this is possibly due to more extensive searches or the fact that 2005 was a particularly good season for the species, resulting in vigorous individuals that were easy to locate.

Limiting factors and threats

At a large scale, the major limiting factor for this species would appear to be the availability of suitable calcareous habitat. However, at a small scale, it is more likely that the main limiting factor for the species is microclimate, especially water availability. Site disturbance along the edge of the trailer park at the largest population (Westport-Sand Lake) has likely resulted in promoting the spread of common buckthorn, an aggressive invasive alien shrub that could significantly alter the fern’s habitat.

Special significance of the species

Canadian populations may have special significance because they are outlying populations at the northern distributional limit of the species. These populations may therefore have particular genetic characteristics, or patterns of genetic variation that are unusual or rare for the species.

Existing protection or other status designations

Woodsia obtusa is listed as endangered under Schedule 1 of the federal Species at Risk Act (SARA). It is listed and protected under the Endangered Species Act in Ontario and under the Loi sur les espèces menacées ou vulnérables in Quebec.

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

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) *

A species of special concern because of characteristics that make it particularly sensitive to human activities or natural events.

Not at Risk (NAR)**

A species that has been evaluated and found to be not at risk.

Data Deficient (DD)***

A species for which there is insufficient scientific information to support status designation.

* 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.

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.