Scouler's catchfly (Silene scouleri ssp. grandis): COSEWIC assessment and status report: chapter 11

Summary of Status Report

Silene scouleri ssp. grandis is at considerable risk in Canada for the following reasons:

  1. The extent of occurrence is very small covering only about 0.6 km² and the area of occupancy is about 1.58 hectare (0.0158 km²).  The distribution is severely fragmented with only two remaining populations with the Trial Island and Little Trial Island plants representing sub-populations.  There is a continued decline in the area and quality of habitat as introduced grasses and shrubs achieve dominance in suitable sites, and there are only two confirmed locations in Canada, and
  2. There are fewer than 350 mature individuals.

Additionally, the persistence of existing populations depends on the protection of fragmented habitats where they occur. There is an increasing threat from aggressive introduced species and from increasing foot traffic through the Trial Island population. Both populations are also at risk from potential marine pollution as they grow close to the intertidal zone of one of the most active oil shipping lanes in North America.

Suitable habitats for Silene scouleri ssp. grandis are extremely rare in Canada and are limited to southeastern Vancouver Island and adjacent local islands. There is negligible opportunity for dispersal of this species to other sites because of its lack of adaptations for seed dispersal and the great scarcity of microsites suitable for germination and establishment.

Populations of Silene scouleri ssp. grandis in British Columbia are at the northern extent of their range and may represent a genetically distinct element important for the long-term survival and evolution of the species.

Funding provided by the Garry Oak Ecosystem Recovery Team and the British Columbia Conservation Data Centre.

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