Frosted glass-whiskers (Sclerophora peronella) COSEWIC assessment and status report: chapter 7

Population Sizes and Trends

The entire known area of coverage for S. peronella, in the three known Canadian locations, is probably no more than one square metre. At each locality, the species was found only once, in spite of repetitive collecting within the localities. Each collection record is interpreted as representing a single contiguous thallus with each bearing several apothecia. Approximately 75% of the apothecia appeared to be mature. It is not known whether these populations are increasing, remaining stable, or are declining in size. The three Canadian occurrences are as follows:

  1. British Columbia, Skeena River Basin, Kitsumkalum Lake, Goward 1991-1139. Trevor Goward (pers. comm.) describes the location as a rather shady cottonwood stand at the south end of Kitsumkalum Lake.
  2. Nova Scotia, Cape Breton Island, Inverness County. Sugarloaf Mountain Wilderness Area, 1998, Selva 7628. Described by the Nova Scotia Department of Natural Resources as an immature old-growth stand and by Selva (1999) as an old-growth stand, this protected northern hardwoods forest is located at the northeast end of Sugarloaf Mountain above East Big Intervale Road.
  3. Nova Scotia, Cape Breton Island, Inverness County, Margaree River Wilderness Area, 1998, Selva 7852. This is another protected northern hardwoods forest described by the Nova Scotia Department of Natural Resources as an immature old-growth stand and by Selva (1999) as an old-growth stand. It was surveyed in its southwestern section, along the north-facing slopes above First Brook Pool.

Estimating “population” size is difficult since field identification has to be verified by microscope studies. In the research that S. Selva has been engaged in over the past 15 years, an assessment of environmental continuity in forested ecosystems is predicated on the compilation of as complete an inventory of the species in the survey area as possible. Since many of these species are rare, even at ancient forest sites, the Relevé Analysis for Classification approach to sampling (Mueller-Dombois and Ellenberg 1974), a form of “intelligent meander”, is preferred. While mindful of the disadvantages of preferential sampling--that of “being biased by subjectivity and of not allowing statistical inferences from the data”, the advantage of “allowing the highest sampling intensity” with “less likelihood of missing localized rich areas” (Nimis 1991) makes this the sampling option of choice. Numerous replicates increase the chances that rarer species would be captured (Selva 1994, 1996). As a result of such intensive collecting, if only a single record is reported for a site--as it has for S. peronella at each of the populations in Nova Scotia, for example, S. Selva is confident in describing the species as extremely rare. To date, the continuity of 76 forests in northeastern North America has been assessed by the S. Selva using the methods described above. In spite of this concerted search effort, S. peronella has been found only twice. Detailed accounts of search effort throughout the species’ range are presented in the section Canadian range, and in Figures 4-6.

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