Rosy owl-clover (Orthocarpus bracteosus) COSEWIC assessment and status report: chapter 4

Distribution

Global range

Orthocarpus bracteosus occurs in western North America, mainly from Vancouver Island south to Oregon west of the Cascades, and southward east of the Cascades to Plumas County, California (Douglas et al. 2000). In Washington, it is only known from Conboy Lake National Wildlife Reserve and Kreps Lane in Klickitat County (southern Washington) and three historical records from San Juan and Whatcom counties in northwest Washington State (1890, 1923, and 1904) (Florence Caplow, Botanist, Washington Natural Heritage Program, pers. comm. Nov 6, 2001). There have been two recent unconfirmed sightings in north-western Washington and botanists continue to search for it there (Terry Domico, Conservation Biologist, Puget Sound BioSurvey, pers. comm., Feb 25, 2001).

Figure 2. Global range of Orthocarpus bracteosus(stars indicate locations of historic, introduced collections).

Figure 2. Global range of Orthocarpus bracteosus(stars indicate locations of historic, introduced collections).

Orthocarpus bracteosus has also been reported for two eastern states, Maryland and New York. The New York collection was from a canal lock in Cayuga County. It was collected in 1918 and was obviously a waif (Charles Sheviak, Curator of Botany, New York State Museum, pers. comm. Feb. 22, 2001). The Maryland collection also appears to be an introduction (Jim Reveal, Professor Emeritus, University of Maryland, pers. comm. Feb. 20, 2001).

Canadian range

Currently in British Columbia Orthocarpusbracteosus is known from 1 extant occurrence and 9 unconfirmed historic localities, all in the Victoria area (BC Conservation Data Centre, February 18, 2002).

Orthocarpus bracteosus has been known in the Victoria area since 1893. Historical records for Sidney, Oak Bay, Victoria and the Patricia Bay Highway are unmappable because the locality is too vague. Historical records of populations at Rollin’s Farm, Blenkinsop (Lost) Lake, Mount Douglas (Cedar Hill) and Beacon Hill are at least 90 years old and no populations have been reported in recent years. They have probably been extirpated.

It is difficult to cross-reference vague collection locations. The Patricia Bay Highway, Blenkinsop Lake, Mount Douglas, Beacon Hill and Trial Island records all certainly refer to distinct populations separated by distances sufficient to ensure negligible genetic interchange. The Sidney collection may have come from the same population as the Patricia Bay Highway collection. The Elk Lake collection may have come from the same population as the Pat Bay collection, in which case the Sidney collection represents a separate population. The Oak Bay collection may have come from Trial Island, although this is unlikely. The Rollins Farm and Victoria collections are so vague that they could have come from the same populations as any of the other collections. In conclusion, collections indicate the past occurrence of possibly nine historic populations, but there is much uncertainty as to how many of these represent distinct populations.

The author searched a number of apparently suitable habitats in 2001, 2002 and 2003 and found no further populations. The search sites included:

All of Trial island, suitable areas on Discovery Island, Mount Douglas, Beacon Hill, Park/Dallas Road Bluffs, east side of Elk and Beaver Lakes, Uplands Park/Cattle Point, Glencoe Cove, Macaulay Point, Saxe Point, Fort Rodd Hill, Ten Mile Point, Little Saanich Mountain (Observatory Hill)

The only population known to be extant is that on Trial Island. The author most recently confirmed this site in August 2003.

In conclusion, there has been a consistent historic downward trend in the number of locations consistent with the urban growth and development of suitable areas on the shore and offshore islets around Victoria. The total extent of the occurrence and total occupancy of Orthocarpus bracteosus in Canada has similarly declined historically and now consists of a single patch covering approximately 300 on Trial Island.

Figure 3. Canadian range of Orthocarpus bracteosus. The single extant island locality in Victoria Harbour is shown as a solid black circle.

Figure 3. Canadian range of Orthocarpus bracteosus.  The single extant island locality in Victoria Harbour is shown as a solid black circle.

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