Grand coulee owl-clover (Orthocarpus barbatus) COSEWIC assessment and status report: chapter 2
COSEWIC
Executive summary
Grand Coulee Owl-clover
Orthocarpus Barbatus
Species information
Grand Coulee owl-clover (Orthocarpus barbatus) is a member of the broomrape family (Orthocarpaceae) and one of nine members of the genus Orthocarpus, of which five species occur in British Columbia and Canada. The species is ayellowish annual herb, reaching 8-25 cm in height. The alternate leaves are stalkless and 2-4 cm long. The yellow flowers are 10-12 mm long, tube-shaped, with yellowish-green bracts. The fruits are elliptical capsules containing several seeds with tight-fitting, netted coats.
Distribution
Orthocarpus barbatusoccurs east of the Cascade Mountains in western North America from the southern Okanagan Valley in south-central British Columbia south to Grant County in south-central Washington. In British Columbia, O. barbatus is known from four sites in the southern Okanagan and Similkameen valleys.
Habitat
The populations in British Columbia are found in the Bunchgrass Biogeoclimatic Zone of southern British Columbia. This zone, particularly in the southern Okanagan Valley, has a cold, semi-arid steppe climate. The Bunchgrass Zone occupies less than one percent of the total area of British Columbia and is one of the most populated and developed areas in the B.C. interior. Orthocarpus barbatusis restricted, within this zone, to extremely dry, open, big sagebrush (Artemisia tridentata) communities at lower elevations in the southern Okanagan Valley, often on sites with sandy to gravelly soils.
Biology
Orthocarpus barbatus is an annual with germination likely occurring in May and with plants senescent by the end of July. Orthocarpus barbatus is likely an outbreeder, primarily pollinated by honeybees and native bee species. Members of the genus Orthocarpus are hemiparasites, and are capable of growing and producing flowers in the absence of a host, but tend to have enhanced growth and reproduction in the presence of a host.
Population sizes and trends
There are four locations for Orthocarpus barbatus in Canada, all in the southern Okanagan Valley and the southern Similkameen Valley. Population sizes range from 185 to approximately 8000 plants on areas of 22 m² to approximately 2000 m². Population trends are not well known and fluctuations are likely natural and due to the annual nature of the genus.
Limiting factors and threats
Orthocarpus barbatus is limited to dry, open, Artemisia tridentata communities at lower elevations, often on sites with sandy to gravelly soils. Alien species, especially newly arrived species, are a major threat to O. barbatus. Currently, the most significant threat to O. barbatus is land development.
Special significance of the species
Populations of Orthocarpus barbatus in British Columbia are unique in that they are at the northern extent of their geographic range. The species has a limited range in North America, and is restricted to the foothills on the east side of the Cascade Mountains of British Columbia and Washington.
Existing protection or other status designations
Orthocarpus barbatus is not covered under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), the Endangered Species Act (USA) or the International Union for Conservation of Nature (IUCN) Red Data Book. NatureServe has designated a global rank of G2G4 for the species (imperiled/vulnerable). In Canada, O. barbatus has a national and provincial rank of N1 and S1 (critically imperiled) respectively. Recent changes in legislation brought about by the passage of the Wildlife Amendment Act of British Columbia allow for the listing and protection of plants under the Act. At this time however, the necessary regulations for the Act are not in place and this species does not occur on the list of four species currently protected under the Act. One of thepopulations of O. barbatus in British Columbia, however, is protected by the Provincial Park Act.
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