Rayless goldfields (Lasthenia glaberrima) COSEWIC assessment and status report 2000: chapter 4

Distribution

Global range

Lasthenia glaberrima ranges from Vancouver Island south, mostly west of the Cascade Mountains, to central California (Figure 2) (Hitchcock et al. 1955, Ornduff 1993). The nearest United States record is from Klickitat County, Washington (Björk pers. comm. 2005). There is a historic record from Clark County, also in Washington. Both of these populations are over 300 km south of the Canadian population and neither is situated along the coast (Washington Natural Heritage Program n.d.). In Oregon, the species occurs in the Willamette Valley but has not been found along the coast (Segotta pers. comm. 2004).

Figure 2. Global range of Lasthenia glaberrima

Figure 2. Global range of Lasthenia glaberrima

Canadian range

In Canada, Lasthenia glaberrima is known from a single population in southwestern British Columbia, near Victoria (Figure 3). The population occupies an area of less than 40 . Since there is only one Canadian population this constitutes both its Extent of Occurrence and its Area of Occupancy. This is considerably less than 1% of the species’ global range. The Extent of Occurrence and Area of Occupancy, as per COSEWIC methodology, are each 1 km² when based on using a 1 km square overlay grid.

Figure 3. Canadian distribution of Lasthenia glaberrima

Figure 3. Canadian distribution of Lasthenia glaberrima

Although Lasthenia glaberrima was not reported in Canada before 2003 there is no evidence that it is a new arrival. The site where it occurs had received relatively little attention from botanists prior to 2003 and most of the earlier botanical exploration in its vicinity occurred in early spring, when winter annuals including Limnanthes macounii(Threatened) are in flower. Even in flower, the species is unlikely to attract attention because of its lack of showy inflorescences. Lasthenia glaberrima is not the only example of a species known from a single widely disjunct location in the Victoria area. Orthocarpus bracteosus is another vernal pool species known from a single location in Canada and, as with Lasthenia glaberrima, the next nearest population is in the Columbia Gorge of southern Washington State. For these reasons, and in the absence of evidence to the contrary, it is prudent to assume that L. glaberrima is a native element of the Canadian flora.

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