Dwarf sandwort (Minuartia pusilla) COSEWIC assessment and status report: chapter 4

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Distribution

Global range

Minuartia pusilla is found in western North America from British Columbia south to Idaho, Arizona and northwestern California (Figure 2; Douglas et al. 1998b).

Canadian range

Minuartia pusilla is only known from a single locality in Canada on southern Vancouver Island, British Columbia (Ceska and Ceska 1980; Douglas et al. 1998b, 2002a, b) (Figure 3). It was discovered only relatively recently in1977, but since it grows in a natural seepage in an undeveloped area with other native species, it is quite unlikely that it was introduced to this site. It was certainly overlooked previous to 1977 due to its occurrence on inaccessible lands restricted from public use (Department of National Defense property (DND)). Also, it may have been overlooked historically, prior to the establishment of the site as a DND property, due its diminutive stature and its superficial similarity to the widespread M. tenella, which occurs in similar habitats. Since its discovery, botanists have scoured the region around Victoria for it with great care and found no further records.

Since 1997 over 150 person search hours by qualified individuals have been conducted at the most likely sites including Trial, Discovery, Griffing Calmer, Saturna Islands, Alpha Islet and Harling and Sax Points and Uplands Park. No additional individuals or populations have been found. In February 2004, specimens of Minuartia tenella at the BC Provincial Museum were checked to see if any overlooked specimens of M. pusilla had been collected, but misidentified. No additional specimens of M. pusilla were found (Jennifer Penny, pers. comm. to David Fraser, February 9, 2004).

This species appears to be similar in distribution to a large suite of species that are found in California and Oregon, but are completely or largely absent from Washington State. This group include species such as Allium amplectens, Crassula erecta (= C. connata),Clarkia viminea, Dryopteris arguta, Isoetes nuttallii, Juncus kelloggii, Minuartia pusilla, Microseris bigelovii, Montia howellii, Myrica californica, Ranunculus californicus, Trifolium depauperatum, Triphysaria versicolor, Vulpia pacifica, Woodwardia fimbriata, etc. (Ceska and Ceska 1997). Distribution of this species is similar to Small-flowered tonella (Tonella tenella), COSEWIC endangered (2003), as it also is found at only one site in the Georgia Depression.