Cliff paintbrush (Castilleja rupicola) COSEWIC assessment and status report: chapter 6

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Distribution

• Global range
• Canadian range

Global range

Castilleja rupicola is limited to the Cascade Mountains, where it is found at moderate to high elevations on rocky ridges, between southwestern British Columbia and central Oregon (Ownbey 1959, Peck 1961, Pojar 2000, NatureServe 2003; Figure 2).

Figure 2. North American range of Castilleja rupicola.

Canadian range

In Canada, C. rupicola is known from the Chilliwack and Skagit River drainages in the Cascade Range of southwestern British Columbia, where it ranges from the upper montane to alpine zones. There is also a 1912 collection from Mt. Brunswick on the southern edge of the Coast Mountains, approximately 115 km west of the occurrences in the Cascade Range (Straley et al. 1985, Pojar 2000, Douglas et al. 2002; Figure 3). The total extent of occurrence of extant populations in Canada is approximately 1000 km². The area of occupancy for Castilleja rupicola is comparatively small; the species only occupies approximately 200-300 m².

Figure 3. Distribution of Castilleja rupicola in southwestern British Columbia.

The nearest site in Washington State is on Church Mountain just below the international boundary at about 122° west.

The writers searched for C. rupicola, above the 1900 m level, on 14 different mountains in the Skagit River drainage in 2003. These 14 mountains represent most (about 80%) of the potential peaks that could support this species in this drainage. The writers had success on only three of these mountains, with only 1-3 plants found on each mountain (Figure 3). This plant is so scarce on these mountaintops that even populations at two known sites (Whitworth and Finlayson Peaks, see Table 1, Figure 3) were not relocated in 2003. The mountain peaks searched unsuccessfully include: Brown Peak, Mount Dewdney, Mount Outram, Johnson Peak, Shawatum Mountain, Finlayson Peak, Unnamed peak (approx. 2 km ENE of Whitworth Peak), Wright Peak, Silverdaisy Mountain, Tulameen Mountain and Whitworth Peak. Two previous collectors of this plant, A. Ceska and F. Lomer (pers. comm., 2003), stated that at their collection sites the plant was extremely sparse. The only potential area not thoroughly searched to date is in the Coast Mountains, between the 1912 collection site (Mt. Brockman) and the Cascade Mountains. There were, however, intensive collections made in this area in the 1950’s and 1960’s, especially by workers from the University of British Columbia, but none of these collections included Castilleja rupicola. At any rate, it is not likely many more sites would be found in the latter area since suitable, vegetated rocky ridges above the 1900 m level are few.

The nearest populations in Washington State are on Church Mountain, Whatcom County, based on a checklist prepared by Deummel (1995-1997) and a collection from high alpine ledges on Church Mountain made in 1934 in Washington State (University of Washington Herbarium [WTU] 2005). This site is about 10 km from the nearest unconfirmed extant site in the mountains of the Chilliwack River sites.