Pink sand-verbena (Abronia umbellata) COSEWIC assessment and status report: chapter 2

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Executive Summary

Species information

Pink sand-verbena, Abronia umbellata, is a member of a genus of 25 species of westernNorth America. Two species occur in British Columbia and three in Canada. Abronia umbellata is represented by a single subspecies (ssp. breviflora) in Canada. The typical subspecies (ssp.umbellata) is found only in California. Abronia umbellata is a perennial herb from a thick, deep taproot. The Canadian plants have trailing stems up to 1.5 m long with short branches and opposite, thick, fleshy, densely glandular leaves. The leaves are lanceolate to narrowly egg-shaped, 2-6 cm long, 0.8-3.5 cm wide with stalks 2.5-7 cm long. The many-flowered, rounded heads occur on stout, 2-4 cm stalks. The flowers consist of a 6-8 mm long, greenish to pinkish perianth tubes that flare into pink, 5-lobed limbs 5-6 mm wide. The fruits consist of 10-12 mm achenes, which are prominently 3- or 4-winged. The wings of the achenes are wider than the achenes. Each achene has a single, brown seed approximately 1.5 mm wide and 3 mm long. 

Distribution

Historically, Abronia umbellata ranged from southwestern British Columbia, south sporadically along the outer coast of Washington and Oregon to northern California.  In Canada, A. umbellata was known, prior to 1927, from Bamfield (Pachena Bay) and Tofino (Ahousat) on the central-west coast of Vancouver Island. Recently it was recollected in 2000 and observed again in 2001 at Clo-oose Bay, south of Tofino. The plant did not reappear in 2002.

Habitat

Abronia umbellata habitat in British Columbia is restricted to upper sand beaches, just below the driftwood zone, along the outer coast. These sites are scoured by high tides and winter storms thus few plants in this zone ever persist over winter. At Clo-oose Bay, the two Abronia umbellata plants were swept away in the first winter storm in October, 2000. A similar situation occurred in 2001. Few plants are adapted to this ephemeral habitat and only scattered specimens of Cakile maritima, a European introduction, occur along this area of the beach. In 2000, two plants of Abronia latifolia were also found on Clo-oose Bay. The sand beach/sand dune habitat is relatively uncommon on the outer coast of British Columbia with only three of the beaches (at Ahousat, Clo-oose Bay and Pachena Bay) having occurrence records of Abronia umbellata. A number of other beaches are potential sites for the species since they support, or have supported, Abronia latifolia , a species with similar habitat requirements.

Biology

Reproduction of A. umbellata is only by seed with a high percentage of all seeds being viable. Germination tests indicate that when fruits are left intact seeds germinate at less than a 1% rate. These experiments suggest that, in the natural environment, Abronia umbellata fruits must be sand-abraded to expose the seeds and subsequently germinate. Stratification treatments involving the naked seeds had germination rates of 52% to 81%. The short-term survival of A. umbellata plants is precarious due to the ephemeral, sandy beach habitat, which occurs within the extreme high-tide zone. Long-term survival, however, is enhanced by the extreme toughness of the fruits although germination rates in the field are low with only 1 in 1000 untreated seeds germinating after scattering on natural beaches. Long-term survival is also highly variable.

Population sizes and trends

Abronia umbellata has been collected at three sites in British Columbia, with the last observation being in 2001. The counts of two and three plants at Clo-oose Bay, in 2000 and 2001, respectively, are the only counts known. The latter plants were washed away at the end of each growing season. It is likely that the seed bank of the ephemeral beach habitat rarely results in large numbers of plants germinating in any given year.

Limiting factors and threats

The greatest threat to the persistence of populations of Abronia umbellata is the invasion and subsequent stabilization of upper beach and foredune systems by Ammophila arenaria and A. breviligulata. At Wickaninnish Beach, Pacific Rim National Park, one of the most extensive beaches on the British Columbia outer coast, this Ammophila invasion has greatly reduced the potential habitat for Abronia umbellata .

The eradication of A. arenaria, because of its extensive underground rhizome network, has proven to be a difficult and challenging problem for land managers. It is now so widespread on the United States west coast that its eradication, except in local situations, is not presently practical. To date, the main eradication techniques have included chemical, manual and mechanical techniques. All of these have met with variable success.

Winter storms are also a major factor. The sand beach habitats of Abronia umbellata are often scoured by high tides and winter storms thus few plants in this zone ever persist over winter. These storms also alter beach and sand dune morphology. The annual phenomena of winter storms, although natural, must be considered for management purposes, especially if reintroduction is considered.

Special significance of the species

Abronia umbellata occurs inan uncommon ecosystem in British Columbia; the sand beach/sand dune system on the outer west coast. The species is also unusual in that it is an ephemeral plant that appears and disappears at lengthy intervals. It is one of the rarest plants in Canada.

Existing protection or other status designations

British Columbia does not have specific legislation in place for the protection of vascular plants at risk. If A. umbellata should re-appear in Pacific Rim National Park Reserve it would be afforded protection under the Canada National Parks Act. COSEWIC listed plants included under the Species at Risk Act will be protected on Federal 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. 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)^Footnote1

A species of special concern because of characteristics that make it particularly sensitive to human activities or natural events.

Not at Risk (NAR)^Footnote2

A species that has been evaluated and found to be not at risk.

Data Deficient (DD)^Footnote3

A species for which there is insufficient scientific information to support status designation.

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.