Seaside centipede lichen (Heterodermia sitchensis) COSEWIC assessment and status report: chapter 4

Distribution

Global range

Heterodermia sitchensiscould be described as essentially endemic to western Canada (Figure 2). Outside of Canada, it is known only from Cape Lookout in coastal Oregon, based on collections made in 2001 (McHenry & Tønsberg 2002). An early report from Alaska (Geiser et al. 1994) is based on a misidentification, notwithstanding later reports to the contrary (McCune & Geiser 1997; Geiser et al. 1998).

Figure 2. Global distribution of Heterodermia sitchensis. Site #1 shows the holotype locality visited in 1983; shaded (red) triangles are localities visited from 2000-2004; and the open circles (sites #1 and #5) are extirpated localities. Numbers correspond to site numbers from Table 1.

Figure 2.  Global distribution of Heterodermia sitchensis. Site #1 shows the holotype locality visited in 1983; shaded (red) triangles are localities visited from 2000-2004; and the open circles (sites #1 and #5) are extirpated localities. Numbers correspond to site numbers from Table 1.

Canadian range

At the time of its description in 1984, H. sitchensis was known from only two localities ('localities' in this report refer to sites of occurrence separated by at least 1 km). Both of these localities are situated on the outer west coast of Vancouver Island, British Columbia. The first (holotype) locality is at Schooner Cove in Pacific Rim National Park Reserve, while the second is 22 km southeast, near Ucluelet on the Ucluth Peninsula. A recent visit to the type locality revealed a drastic decline from about 12 thalli in 1983 to only 1 moribund thallus in 2002, now also presumed to have disappeared. In addition, logging for a housing development at the Ucluelet locality led, in the early 1990s, to the disappearance of H. sitchensis here (Goward, personal observation).

Recent studies funded by Parks Canada from 2001 to 2004 have extended the known range of H. sitchensis south to Folger Island (48°49'N), and north to the vicinity of Kyuquot (49°59'N). Work to date has confirmed early impressions that H. sitchensis is a rare species with a sporadic distribution. In Canada, it has been recorded from a total of only 12 localities, ten of which occur in or near Pacific Rim National Park Reserve. The remaining two localities are situated near Kyuquot (Figure 2). Ten localities have been either found or confirmed since 2001, while the remaining two (Ucluelet and the holotype locality) apparently no longer support H. sitchensis.

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