Mountain holly fern (Polystichum scopulinum) COSEWIC assessment and status report: chapter 4

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Distribution

Global range

Polystichum scopulinum ranges from southwestern British Columbia, sporadically south in the western United States to Colorado, Arizona and California (Figure 2, Wagner 1993). It is also disjunct to northeastern Quebec and western Newfoundland (Figure 2, Wagner 1993).

Canadian range

In Canada Polystichum scopulinum is known from three areas, one in British Columbia, one in Quebec and one on the island of Newfoundland. In British Columbia there are three populations (including two sub-populations on Grasshopper Mountain) in the Tulameen River (Figure 3; Ceska 2000; Douglas et al. 2002a, b). In Quebec, it is known from Mont Albert on the Gasp¨¦ Peninsula (Figure 4; Labrecque and Lavoie 2002). A population was recorded in 1950 from Humber West (North Arm) in western Newfoundland (Bouchard et al. 1991; Meades et al. 2000). A limited search was conducted on North Arm Mountain in 2000 but no plants were located (Djan-Ch¨¦kar, pers. comm. 2004). The site is remote and the original location and habitat description provided by Rouleau, the collector, are quite general. It may be premature to presume that the population is extirpated (Djan-Ch¨¦kar, pers. comm.).

Polystichum scopulinum was first collected in BC on Olivine Mountain, Tulameen River valley in 1952 by A.R. Kruckeberg. All three populations in the Tulameen Valley (Figure 3) were visited and assessed in 1996 by G.W. Douglas. In 2002, G.W. Douglas returned to, and assessed, the Britton Creek population.

Throughout its North American range P. scopulinum occurs only on ultramafic (serpentine) soils (Kruckeberg 1969). In British Columbia, there are approximately 20 of these ultramafic localities, with only one of them supporting P. scopulinum. Almost all ultramafic localities have been searched thoroughly since these localities always support one or more of three rare Polystichum species (P. kruckebergii, P. lemmonii and P. scopulinum) and are of special interest to botanists. In southern Quebec, the main other area of serpentine bedrock is around the highly disturbed asbestos mining area of the Thetford Mines in the Eastern Townships. These have been surveyed extensively. The fern is likely absent here because it tends to be alpine in nature and the outcrops in the Eastern Townships are at low elevations.