Showy phlox (Phlox speciosa): COSEWIC assessment and status report: chapter 2

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COSEWIC Executive Summary

Species information

Only a single subspecies of showy phlox, Phlox speciosassp. occidentalis, is known from Canada. The species is therefore referred to simply as Phlox speciosathroughout the report.  It is a perennial plant with a somewhat shrubby base. Stems are erect, 15-40 cm tall, rising from a woody taproot. The plant is glandular to glandular-hairy above, and hairy below. The opposite leaves are linear to lance-shaped, to 7 cm long and 1 cm wide. The plant has clusters of flowers at the ends of stems, with leafy bracts. Corollas (joined petals) range from pink to white. The corolla tube (1-1.5 cm long) spreads to five wide lobes (1-1.5 cm long) that are notched at the tip. Calyces (joined sepals) are glandular, with flat, transparent segments between the five green ribs. Styles range from 0.5-2 mm long.

Distribution

Historically, the taxon is known to occur in the Okanagan Valley from Summerland in the north, south to Skaha Lake (formerly Dog Lake), and southwest to the Twin Lakes. Extant and newly discovered populations are concentrated in a cluster around Yellow Lake and Twin Lakes, between the towns of Keremeos and Penticton. The known extent of its range in British Columbia is about 57 km². The area of habitat occupied at the known populations is estimated to be between 0.9-1.4 km².

Habitat

Phlox speciosa seems to require the following habitat features: a very hot, dry, interior climate; open Pseudotsuga menziesii (Douglas-fir) and/or Pinus ponderosa(ponderosa pine) forests or Artemisia tridentata (big sagebrush) shrub/grasslands; a specific range of elevations (700-1100 m); and cool aspect slopes or level sites.

Biology

Little specific information is available on the biology of Phlox speciosa. The plant is a perennial, and reproduces by seed.

Population sizes and trends

Nine populations and 20 sub-populations of Phlox speciosa are known to be extant in Canada. Four of the populations and several of the sub-populations were discovered in 2003. Two or three historical populations have not been relocated, and may be extirpated. A total of 6,400-57,000 mature reproducing individuals are estimated to exist in Canada. Almost no information was available on population sizes prior to 2003, so trends in population sizes for the taxon cannot be characterized.

Limiting factors and threats

A potential threat to Phlox speciosa populations is the lack of protection of natural plant communities throughout the majority of the plant’s range in Canada. Within the current extent of occurrence, 41% of the area is privately owned land, which is particularly vulnerable to changes in land use and development, including range reseeding. Increasing recreational property development represents the most important trend in habitat loss. Canadian populations are also potentially vulnerable given their relatively small area of occupancy. Another potential threat is weed control activities required by the Weed Control Act. Use of marginally specific herbicides that kill broad-leaved plant species would likely kill Phlox speciosa.

Special significance of the species

Canadian populations of Phlox speciosa occur at the northern extent of their geographic range. Although so-called “peripheral” populations have often been assigned low priority for conservation, the importance of populations at the edges of their ranges is increasingly being recognized. As its common name suggests, Phlox speciosa is also a very showy and attractive plant. It has been used as a horticultural species in appropriate North American climates.

Existing protection or other status designations

No legal protection specifically protects Phlox speciosa populations in any part of its range. The taxon has a Subnational Natural Heritage Status Rank of Critically Imperiled (S1) in British Columbia, indicating that it is extremely rare or especially vulnerable to extirpation. A portion of one population occurs on federal land that is being managed by the Nature Trust. Other populations occur on private land and on non-protected provincial crown land.

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^th2003, 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 agencies (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 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 (November 2004)

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 it is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for atleast 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)¹

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)²

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

Data Deficient (DD)³

A wildlife species for which there is inadequate information to make a direct, or indirect, assessment of its risk of extinction.