Foothill sedge (Carex tumulicola) COSEWIC assessment and status report: chapter 4

Distribution

Global range

Carex tumulicola is found west of the Cascade Mountains from southern Vancouver Island to central California (Figure 2). The Vancouver Island plants, along with nearby populations in north Puget Sound, are disjunct by approximately 300 km from the species’ main range which ends just north of the Columbia River. A 1935 collection from Mount Rainier (J.W. Thompson 12551) has been re-identified as a depauperate specimen of Carex preslii (P. Zika, pers. comm. 2004). The species’ main range extends upstream along the Columbia River as far as Bingen, southwards along the coast and the Willamette Valley to California. In California, C. tumulicola occurs both along the Coastal Ranges and the Sierra Nevada Foothills (Douglas et al. 2001, Hitchcock et al. 1969, Mastrogiuseppe 1993). Carex tumulicola has been reported in Idaho, based on collections from Owyhee county in southwestern Idaho, and historical collections from Bannock and Power counties in the eastern part of the state (Idaho Fish and Game 2004). These reports are suspect, however, and the material should be re-examined to see if they are misidentifications of other, more likely species such as C. occidentalis orC. hookeriana.

Canadian range

In Canada, Carex tumulicola has only been found along the southeast coast of Vancouver Island (Figure 3). Most known populations occur in or near Victoria. It has been collected as far north as Nanaimo and as far west as Rocky Point (east of Sooke). The nearest U.S. populations occur in the San Juan Islands, only a few km from Victoria. A population is known from Port Townsend, also <20 km from Victoria.

Figure 2. Global range of Carex tumulicola. Stars are unconfirmed collections.

Figure 2.Global range of Carex tumulicola

Figure 3. Range of Carex tumulicola in Canada. Solid circles: extant populations; white triangles: survey locations where C. tumulicola was not found.

Figure 3. Range of Carex tumulicola ire 3. n Canada.

Since 1990, when Carex tumulicola was first collected on Vancouver Island, the number of known populationsFootnote1 in Canada has increased from one to ten. The actual area of habitat occupied by the species is ≤ 1 km²; this has increased from a few at the original location to an estimated 100 ha. The COSEWIC Area of Occupancy, if based on a 1x1 km grid, is 10 km² and 32 km² if a 2x2 km grid is applied. The Extent of Occurrence (EO) is now estimated at 1, 700 km². These increases almost certainly do not reflect any recent biological expansion in the range ofC. tumulicola. Rather, they may be presumed to reflect the increased attention and search effort the species has received from local botanists since 1998.

Page details

Date modified: