Dwarf Woolly-heads Prairie population
Scientific Name: Psilocarphus brevissimus
Taxonomy Group: Vascular Plants
Range: Alberta, Saskatchewan
Last COSEWIC Assessment: April 2006
Last COSEWIC Designation: Special Concern
SARA Status: Schedule 1, Special Concern
Image of Dwarf Woolly-heads
Two varieties of Dwarf Woolly-heads are recognized: the typical brevissimus variety and the multiflorus variety. Because this species is represented in Canada only by the brevissimus variety, the name “Dwarf Woolly-heads” is used here without specifying the variety.
The Dwarf Woolly-heads is a woolly annual with a short root. Its stems are prostrate, matted and 8 to 20 cm long. It has few leaves, which are covered with fine white woolly hairs and inserted directly into the stem in opposing pairs. They resemble triangular lances or narrow lances with their ends more or less rounded. They are 4 to 15 mm long. The flowers are grouped in disc-shaped heads located in the leaf axils where the leaves meet the branches, or at the tips of the branches. Small hooded and balloon-like leaves, 2.4 to 4 mm long, grow at the base of the flower heads. The dry fruits, called achenes, are more or less cylindrical. They are 1 to 2 mm long and hairless.
Distribution and Population
The range of Dwarf Woolly-heads extends from south-central British Columbia south to Montana and Utah in the western United States to Baja California, Mexico. It also occurs in Chile and Argentina. In Canada, Dwarf Woolly-heads is known from only the Similkameen Valley south of Princeton in south-central British Columbia and from southeastern Alberta and southwestern Saskatchewan. The Southern Mountain population (British Columbia) and the Prairie population (Alberta and Saskatchewan) are separated by a distance of over 500 km and several mountain ranges. Like all annual plant populations of vernal pools and temporary ponds, the Prairie population fluctuates greatly from year to year, depending on rainfall and flooding. It may have as few as 2000 mature individuals in “trough” years and perhaps as many as 27 000 in “peak” years. It is therefore difficult to predict long-term trends in this population.
The Dwarf Woolly-heads grows in chalky clay soils in vernal pools in large forest openings dominated by two other flowering plants: Scouler’s Popcornflower and the Close-flowered Knotweed. This annual also grows at the edges of ephemeral ponds on this same type of soil, which is wet in spring but becomes dry and compacted in summer. The sites where the Dwarf Woolly-heads populations occur are on level to gently sloping terrain. The species shows a high tolerance both for spring floods and summer heat and drought.
Little information is available on the biology of the Dwarf Woolly-heads. However, it is known that, in British Columbia, this species flowers in June when the inundated vernal pools are increasingly saturated with water. A study of the plant’s flowers and its lack of any features to attract pollinating insects suggest that this species probably reproduces by self-pollination. This means that its flowers are fertilized by their own pollen. However, pollen may not be essential for the production of seeds and the species may in fact reproduce without fertilization. The Dwarf Woolly-heads produces its fruits when the pond has dried up. Its seeds may be dispersed by animals. Various species of birds that use the vernal ponds might carry the seeds over short or long distances. Cottontail rabbits, including Nuttall's Cottontail, which lives in the grasslands of this region, may also help to disperse seeds between vernal ponds in proximity to each other.
The factor that constitutes the most immediate threat to the populations of Dwarf Woolly-heads in British Columbia, and hence in Canada, is the smallness of the area that they occupy. This factor makes them highly vulnerable. Also, because the habitats suitable for this species are extremely limited, the opportunities for colonization and expansion are limited too. The recreational use of all-terrain vehicles, which has been observed near the Dwarf Woolly-heads sites, constitutes another definite threat. These vehicles could alter the habitat so much that it would no longer be suitable for this species and would favour invasive exotic plants. The populations are located on two private properties that are part of British Columbia’s Agricultural Land Reserve, which is mainly used for agriculture. Some of the activities allowed in the reserve are not necessarily compatible with the habitat requirements of this species. Lastly, weed-control measures pose another potential threat. The chemicals used to destroy nuisance plants are not very specific and could kill the Dwarf Woolly-heads.
Federal ProtectionMore information about SARA, including how it protects individual species, is available in the Species at Risk Act: A Guide.
Provincial and Territorial Protection
Prairie Plant Species at Risk Recovery Team
Candace Neufeld - Chair/Contact - Environment Canada
Phone: 306-975-4101 Send Email
PLEASE NOTE: Not all COSEWIC reports are currently available on the SARA Public Registry. Most of the reports not yet available are status reports for species assessed by COSEWIC prior to May 2002. Other COSEWIC reports not yet available may include those species assessed as Extinct, Data Deficient or Not at Risk. In the meantime, they are available on request from the COSEWIC Secretariat.
9 record(s) found.
- COSEWIC Status Reports (1 record(s) found.)
- COSEWIC Assessments (1 record(s) found.)
- Response Statements (1 record(s) found.)
- Management Plans (1 record(s) found.)
- Orders (2 record(s) found.)
- COSEWIC Annual Reports (1 record(s) found.)
- Consultation Documents (1 record(s) found.)
- Recovery Document Posting Plans (1 record(s) found.)
COSEWIC Status Reports
COSEWIC Annual Reports
COSEWIC Annual Report - 2006 (2006)2006 Annual Report to the The Minister of the Environment and the Canadian Endangered Species Conservation Council (CESCC) from the Committee on the Status of Endangered Wildlife in Canada.
Recovery Document Posting Plans
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