Dwarf sandwort (Minuartia pusilla) COSEWIC assessment and status report: chapter 2

COSEWIC Executive Summary

Dwarf Sandwort
Minuartia pusillia

Species information

Dwarf sandwort (Minuartia pusilla) is a member of the Pink or Caryophyllaceae family. It is an annual herb with a weak taproot. The plant is 2-5 cm tall with solitary or few erect stems that are simple to branched and smooth, white-waxy in appearance.  The basal and lower stem leaves are opposite and linear, and the upper stem leaves are few, similar, not much reduced and without stipules. The flowers are arranged in an open, leafy-bracted cluster that is often 4/5 the total height of the plant. The petals are sometimes lacking. The fruits are egg-shaped capsules that are 3-valved.

Distribution

Dwarf sandwort is found in western North America from British Columbia south to Idaho, Arizona and northwestern California. It is only known from one location in Canada in southwestern British Columbia at Rocky Point on southern Vancouver Island. The nearest known occurrence south of Rocky Point is in Klickitat County in the very southern portion of Washington State.

Habitat

Dwarf sandwort is found in a climatic and floristic anomaly in coastal British Columbia, the Coastal Douglas-fir Zone. Within this zone, it occurs in a small vernal seep on the flat top of a coastal headland with about four inches of moraine. The southeast sloping (0-24%) depression is wet in the spring and mesic to dry later in the season. The soil types are rapidly draining sandy moders (a type of sandy humus) with no soil moisture late in the season and poor nutrient content. 

Biology

Dwarf sandwort likely germinates in December or January in British Columbia and reaches reproductive age within one year. It potentially over-winters in the seedling stage, and therefore behaves as a winter annual with flowers developing in May or June. It is a strict ephemeral that is greatly reliant on precipitation before and during the growing season for its germination and longevity. Dwarf sandwort has tiny flowers, and lacks nectar glands and occasionally petals. Furthermore, the anthers open prior to floral expansion, thus suggesting that it is exclusively self-pollinated.

Population Sizes and Trends

There is only one known location for dwarf sandwort in British Columbia. When it was first observed in 1977, there were approximately 20 plants over about 10 and when it was last observed in 2002, there were 9 plants over the same area. Annual ephemerals often experience year to year changes in population size dependant on changing climatic conditions, so the decline may not represent a significant trend. Numerous surveys have been made in the region to locate new populations with no success.

Limiting Factors and Threats

Dwarf sandwort, diminutive in stature, is likely quite sensitive to physical disturbance. It is also likely susceptible to any physical or chemical changes to the vernal seep it inhabits. Actual threats include digging by gulls and possibly trampling by trespassing boaters. In the winter of 2002 to 2003, soils were churned up by gulls in the immediate vicinity of the site. Introduced annuals could become a problem in the future. Mosses could also pre-empt dwarf sandwort at the site. Numbers of dwarf sandwort likely fluctuate from year-to-year, but if in any given year, critical moisture is not available for germination and seedling development, it is possible that the species could disappear altogether. Likewise, if the habitat is too wet, conditions could become unsuitable.

Special Significance of the Species

As dwarf sandwort is at the northern range limit of the species in North America, there are potentially genetic differences in this population from other populations south across the Canadian-U.S. border. Genetically distinct peripheral populations may be important for the long term survival of the species as a whole.

Existing Protection or Other Status Designations

Globally, dwarf sandwort is common to very common and demonstrably secure and essentially ineradicable under present conditions.  Provincially, however, the British Columbia Conservation Data Centre in the Ministry of Sustainable Resource Management has ranked this species as “S1” (critically imperiled) and placed it on the “Red list. “

Recent studies on rare plants on the Department of National Defense properties where dwarf sandwort occurs will be considered in a natural resource management plan.

COSEWIC History

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed  under a rigorous and independent scientific process.

COSEWIC Mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species and include the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC Membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal organizations (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biosystematic Partnership, chaired by the Canadian Museum of Nature), three nonjurisdictional members and the co-chairs of the species specialist and the Aboriginal Traditional Knowledge subcommittees. The committee meets to consider status reports on candidate species.

Definitions (after May 2004)

Species
Any indigenous species, subspecies, variety, or geographically defined population of wild fauna and flora.

Extinct (X)
A species that no longer exists.

Extirpated (XT)
A species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)
A species facing imminent extirpation or extinction.

Threatened (T)
A species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)Footnotea
A species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.

Not at Risk (NAR)Footnoteb
A species that has been evaluated and found to be not at risk.

Data Deficient (DD)Footnotec
A species for which there is insufficient scientific information to support status designation.

 

Canadian Wildlife Service

The Canadian Wildlife Service, Environment Canada, provides full administrative and financial support to the COSEWIC Secretariat.

 

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