Cryptic paw (Nephroma occultum) COSEWIC assessment and status report: chapter 2

COSEWIC Executive Summary

Cryptic paw
Nephroma occultum

Species information

Nephroma occultum is a rare lichen, endemic to Western North America. It is strongly associated with humid old growth forests and is characterized by a yellowish, greenish, or bluish-grey upper surface with net-shaped ridges, and a hairless tan to sometimes blackish lower surface. It is commonly is 2-7 cm broad and has rounded lobes 4-12 mm wide. It produces many asexual propagules, called soredia, along the margins and the ridges of the upper surface, and lacks apothecia, the spore-producing sexual stage of reproduction.

Distribution

The global distribution of Nephroma occultum is captured within the geographic boundaries of Alaska (6 localities), British Columbia (45), Washington (8) and Oregon (182). The Canadian portion of the range accounts for more than 50% of the total spatial distribution, and coincides with the intermontane valleys of the Coast Range and the Columbia Mountains.

Habitat

In Canada, Nephroma occultum is confined to moist old growth forests at elevations below 1200 m.  All Canadian populations occur in the Coastal Western Hemlock Zone and the Interior Cedar-Hemlock Zone of the British Columbia Biogeoclimatic Ecosystem Classification system (Meidinger and Pojar 1991). Avoidance of summer drought is a key attribute of N. occultum habitat. In coastal localities the macro-climate provides sufficient moisture for N. occultum to inhabit the upper forest canopy. In inland regions where the macro-climate is often too dry, N. occultum is restricted to the lower canopy of humid old growth forests.

Biology

Nephroma occultumproduces large numbers of asexual soredia which are thought to be dispersed by wind, rain and animals. The soredia of N. occultum are larger than those of most lichens, and poor propagule dispersal appears to be a factor which limits distribution. N. occultum does not have sexual structures (apothecia) and may have low genetic variation. Furthermore, N. occultum is a poor competitor and is displaced by mosses or liverworts where these are the dominant epiphytes.

Population sizes and trends

As of 2004, the global distribution of Nephroma occultum comprises approximately 241 known extant populations, of which 45 are located in Canada. Extirpation at two sites within Canada is attributable to forest harvesting. Populations vary in size among extant localities from single thalli to 40 or more within a single stand. With a conservative estimate of 10 thalli per stand, there are probably more that 2,410 individuals of Nephroma occultum worldwide.

Limiting factors and threats

Nephroma occultum is limited by the availability of suitable habitat (humid old growth forests) and poor dispersal efficiency. Humid, old growth cedar-hemlock forests have diminished in abundance in step with the progressive expansion of forest harvesting. Additional threats from hemlock looper infestations and fire are predicted to increase in severity and frequency as mean annual temperatures rise, reflecting global warming. Cumulative effects of harvesting, climate change, insect infestations and fire are expected to have a negative influence on remaining N. occultum habitat.

Special significance of the species

Nephroma occultum is endemic to western North America, and Canada accounts for more than 50% of the entire global range. Only five Canadian populations are protected from forest harvesting. N. occultum is a “flagship” species among a suite of rare and uncommon lichens and bryophytes that are dependent upon humid, old growth forests, many of which exhibit an unusual coastal-inland disjunct distribution. Where regulations require rigorous lichen surveys (for instance, in Oregon), the discovery of this lichen has led to progressive forest management practices encouraging the retention of remnant old growth tree patches. However, throughout the Canadian portion of the range, N. occultum habitat is in progressive decline, primarily due to forest harvesting. This trend is most pronounced in the inland areas where suitable habitat is geographically restricted by the availability of forests with humid micro-climates.

Existing protection or other status designations

Nephroma occultum was designated a species of Special Concern by Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in 1995 based upon recommendations from the initial status report (Goward 1995a). In British Columbia it is ranked S2S3 and is not protected by provincial legislation. Five Canadian localities for N. occultum are situated within parks or protected areas. The remaining populations occur on Crown Land and are not protected from forest harvesting or other disturbances. In Washington (S1) and Oregon (S3), N. occultum is a listed species on the Northwest Forest Plan, meaning that developers must survey and manage for this species according to the plan’s guidelines. N. occultum also occurs in Alaska where it is not protected.

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 5th 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 (2006)

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 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.

 

Canadian Wildlife Service

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

 

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