Dwarf sandwort (Minuartia pusilla) COSEWIC assessment and status report: chapter 7

Population Sizes and Trends

There is only one known location for M. pusilla in British Columbia. It was first observed in 1977. Adolf and Oluna Ceska have sought out suitable habitats for this species in the region since the discovery in 1977 (A. Ceska, pers. comm.). In 2002, they were also commissioned to do another detailed survey for it in suitable habitats, but no new sites were found. A population of approximately 20 plants over about 10 were enumerated in 1977 and 9 plants were observed in 2002 over the same area (A. Ceska, pers. comm.). As this population has not been monitored, we do not know the year-to-year changes in population size; however, a decrease in numbers from 1977 to 2002 indicates a 55% decline over a 25 year period. One should be cautious in interpreting the decline as annual ephemerals can experience large changes in numbers from year to year depending on climatic conditions. It appears that M. pusilla has remained relatively stable at a very low effective population size at the single Canadian site.

Although this species exists in Washington State, it is unlikely that any immigration would occur. The nearest known location in Washington is in Klickitat County in the very southern portion of the state over 300 km distant.

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