Short-rayed alkali aster (Symphyotrichum frondosum) COSEWIC assessment and status report: chapter 2

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COSEWIC Executive Summary

Species information

The short-rayed alkali aster, Symphyotrichum frondosum, is a late emergent shoreline species reported primarily from lakeshore habitats in moist drawdown zones of sandy beaches and perimeters of alkali lakes and ponds in British Columbia. It is found primarily in the bunchgrass biogeoclimatic zone (Douglas et al. 1998) of the sagebrush steppe in the southern Okanagan Valley. A single ephemeral population in sand dredgings on the shore of the Fraser River in Surrey may represent the presence of the species upstream in the Fraser-Thompson drainage.

It is a small, many-branched annual herb 5-60 cm in height, arising from a taproot. The numerous flower heads support multiple flowers. Flowers are white to pink in colour, with both ray petals, and yellow disk flowers. Plants are generally submersed until late summer, with flowering occurring in August and early September.

Distribution

Globally, the short-rayed alkali aster is known only from Mexico, the US and Canada. In the US it is found in California, Arizona, New Mexico, Nevada, Colorado, Idaho, Montana, Utah, Oregon, Washington, and Wyoming. In Canada it is known only from British Columbia, primarily in the Okanagan Valley.

Habitat and biology

This shoreline species is adapted to fluctuating water levels and late summer drawdown. Dispersal is likely by wind, water, and small mammals. The species can withstand high pH and high salinity.

Population sizes and trends

Four extant stations for short-rayed alkali aster are confirmed in British Columbia. Limited data are available for all populations so trends cannot be fully assessed. One population was ephemeral. One sub-population has been extirpated, and one new sub-population is reported. The extent of occurrence (total area encompassed within a convex polygon that includes all populations) is approximately 56 km². The combined area of occupancy (total area of suitable habitat over which the plants occur) is 900 m², but the area of occupancy for several sites is unknown.

Limiting factors and threats

Beach maintenance activities and heavy beach use (trampling and severe disturbance) limit the areal extent of populations at three stations, and threaten the persistence of the populations. Additionally, invasive plant species may be another serious threat.

Special significance of the species

In Canada, short-rayed alkali aster occurs at the northern limit of its range, and is important ecologically, biogeographically and genetically because of this.

Existing protection

One station occurs in a provincial park, and a second station occurs partly in a provincial park. This provides legal protection, but no formal protection exists. A third station occurs on lands with a conservation covenant. A fourth station (four reported sub-populations) occurs primarily in Indian Reserve lands.

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. Species designated at meetings of the full committee are added to the list. On June 5^th 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 for 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 entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

Definitions (2006)

Wildlife Species

A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.

Extinct (X)

A wildlife species that no longer exists.

Extirpated (XT)

A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)

A wildlife species facing imminent extirpation or extinction.

Threatened (T)

A wildlife species likely to become endangered if limiting factors are not reversed.

Special Concern (SC) ^Footnote1

A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.

Not at Risk (NAR) ^Footnote2

A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data Deficient (DD) ^Footnote3

A category that applies when the available information is insufficient (a) to resolve a species’ eligibility for assessment or (b) to permit an assessment of the species’ risk of extinction.