Lindley’s false silverpuffs (Uropappus lindleyi) COSEWIC assessment and status report: chapter 7

Population Sizes and Trends

Search effort

Uropappus lindleyi is often found in steep, somewhat inaccessible microhabitats, which may explain the lack of records of this species prior to its first observation in 1974. Casual surveys of potential U. lindleyi habitat have been conducted by botanists over the last 30 years with little success. A comprehensive search of suitable habitat was conducted in 2003 and 2004 by several botanists searching habitats specifically for U. lindleyi (see Appendix 1 for unsuccessful search sites). It is possible, however, additional populations may exist in small patches at sites not thoroughly searched. Further details of search effort are not available because the primary writer (George Douglas) is now deceased.

Abundance

There are five extant U. lindleyi locations in Canada. All of these are in the Gulf Islands (Figure 4, Table 1). One population was recorded on southern Vancouver Island in 1998. This site, revisited by the authors in 2004, is now considered extirpated due to the construction of a housing development that has completely obliterated most of the slope on which it occurred. Existing population sizes range from approximately 20 to 1200 plants, on areas of less than one square metre up to one hectare.

The most recent observations of the five U. lindleyipopulations in British Columbia, made in 2003 and 2004 (Figure 4) indicate that there are a total of about 2000 individuals (Table 1).

Table 1. Locations and population sizes for Uropappus lindleyi in British Columbia.
Population Last Observation Observer Number of Plants/Area
North Pender Island
1996
Penny 20/? m² – 2004 search unsuccessful
Vancouver Island
2004
Douglas and Smith Extirpated
Ruxton Island
2003
Ennis 800/1 ha
Saturna Island: Population 1

2003

Janszen

22+/0.7 m²
Saturna Island: Population 2
2004
Douglas & Smith 28/8 m²
Galiano Island: Subpopulation 1

2003

Janszen

390/512 m²
Galiano Island: Subpopulation 2
2004
Douglas & Smith 800/440 m²

Fluctuations and trends

Population trends are not known, and will be difficult to assess due to the annual nature of the species.

Rescue effect

The potential for rescue from the species’ main range, 300 km away on the east side of the Cascade Mountains in the U.S., is unknown but could be considered to be highly unlikely. Even locally, the amount of genetic exchange between populations is unknown. Canadian populations are fragmented, with distances of 10-15 km between populations.

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