Golden paintbrush (Castilleja levisecta) COSEWIC assessment and status report: chapter 2

COSEWIC Executive Summary

Golden Paintbrush
Castilleja levisecta

Species information

Golden paintbrush (Castilleja levisecta) is a perennial herb, usually producing several clustered stems from a common base. The hairy leaves are alternate and attached to the stem. The lower leaves are simple and narrow while the upper leaves are egg-shaped and have 1-3 pairs of short lateral lobes. The inflorescence is a prominently bracted terminal spike. The bracts are hairy, large, golden yellow, blunt and about as wide as the upper leaves. The tips of the bracts have 1-3 pairs of short lobes. The flowers are largely concealed by the bracts. The corolla consists of fused petals that form a 2-lipped structure at the end of a corolla tube. The upper lip is beak-like and 3-4 times as long as the lower lip. There are four stamens and a single stigma and style. Fertilized ovaries develop into a dry capsule that contains 70-150 minute seeds which have a loose, net-veined seed coat.

Golden paintbrush has a chromosome count of 2n=24. Studies have shown that exceptionally high levels of genetic diversity are maintained within the species compared with other narrowly endemic plant species. The Trial Island population, though one of the most geographically isolated, was the most genetically diverse and showed relatively low levels of genetic divergence. In contrast, the Alpha Islet population showed the second highest level of genetic convergence but only middling levels of genetic diversity.

Distribution

The species occurs at low elevations west of the Cascade Range from Vancouver Island to Linn County, Oregon. In Canada, Golden paintbrush is found only on small islands offshore of Victoria, British Columbia. The two extant populations are approximately 7 km apart and the extent of occurrence is about 2.2 km². The historic extent of occurrence appears to have been approximately 100 km². The area of occupancy is a maximum of 4 km² when based on a 2 km x 2 km grid.

Habitat

In Canada, golden paintbrush occurs in maritime meadows. Summer temperatures are greatly moderated by proximity to the ocean. Coastal fogs bring heavy dew in the late summer and early fall, stimulating germination and breaking shoot dormancy in many perennials even as inland areas remain dry and brown. Coastal fogs and the proximity to shoreline also tend to moderate winter frosts (particularly at night), retard the accumulation of heat and may slow down the development of plants, particularly in the late spring. Maritime meadows may be largely free of woody vegetation for a variety of reasons, including strong summer moisture deficits (particularly on wind-exposed sites and/or those with thin, coarse-textured soils), salt spray and a long history of burning by First Nations. These forces may act alone or in concert, consequently some maritime meadows are subject to forest ingrowth while others remain open despite fire suppression.

The amount of potential habitat on southeast Vancouver Island and the adjacent offshore islands has declined greatly over the past century as maritime meadows have been developed for residential and recreational use. There are approximately 24 ha of maritime meadow habitat within the current range of golden paintbrush in Canada. The distribution of golden paintbrush in Canada lies at the heart of one of North America’s fastest growing regions. As a result, there will be continued pressure to develop maritime meadow habitat capable of supporting the species.

Approximately 90% of the current area of occupancy was subject to long periods of livestock grazing in the past and now has vegetation dominated by invasive grasses and forbs as a result. An even greater proportion of potential, but unoccupied, habitat has been grazed by livestock in the past; and is now also dominated by invasive grasses and forbs. Even areas that do not appear to have been grazed in the past have been altered as a result of invasion by herbaceous non-native species, which may still be increasing in abundance.

Burning by First Nations, to improve camas crops, maintained maritime meadow habitat in the past. Fire suppression now favours the development of dense patches of native shrubs and trees where golden paintbrush cannot survive.

Biology

Shoot dormancy begins to break as early as mid-September, and by January most shoots have broken dormancy. Most shoots begin to elongate in March, as the leaves fill out and internodes elongate. Flowering peaks in April and May. Green fruits develop from May to July and ripe, undehisced fruit are usually present from July to early September. Seeds are gradually shed until late November or December, at which point most ripe seeds have dispersed. The seeds are minute, lack adaptations to assist in long-distance dispersal, and appear to be shed when wind shakes the ripened plants.

Golden paintbrush, as a taprooted perennial, is incapable of clonal growth through asexual reproduction.

Herbivory by mammals and arthropods may have a negative effect on the species, but the Canadian populations occur on islands free of mammalian herbivores and arthropod herbivory has only a minor impact.

Golden paintbrush is a hemiparasite, containing chlorophyll and fixing carbon through photosynthesis but receiving water and nutrients through parasitic root connections. It probably parasitizes a broad variety of species.

Population sizes and trends

Golden paintbrush has been reported from eight locations in Canada, only two of which have extant populations. Based on the most recent data there was a total of 3,361 flowering plants in Canada in 2006.  This appears to represent a population decline of about 25% over the past 10 years, primarily at Alpha Islet. The potential for a rescue effect is slight because nearby populations in the United States are small and separated by over 10 km of open ocean, and because the seeds are poorly adapted to long-distance transport.

Limiting factors and threats

Apart from the threats to habitat – discussed above – golden paintbrush has been threatened in the past by spring and early-summer mowing, herbivory and trampling.

Special significance of the species

Canadian populations of golden paintbrush have a very high conservation value because they represent approximately 20% of the entire global population of a narrowly-distributed endemic. In some areas, golden paintbrush may have been an important host plant of Taylor’s Checkerspot, a Nationally Endangered butterfly.

Existing protection or other status designations

The Nature Conservancy has ranked golden paintbrush as globally critically imperilled. It is listed as Threatened under the U.S. Endangered Species Act. In 2000, COSEWIC ranked golden paintbrush as Endangered in Canada based on a report prepared in 1995.

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, 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 (2007)

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

Data Deficient (DD)Footnotec
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.

 

Canadian Wildlife Service

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

 

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