Silene douglasii var. oraria
|Cascade head catchfly|
|(M.E. Peck) C.L. Hitchc. & Maguire|
|Edward Guerrant, Ph.D.|
The following Participating Institutions are custodians for this species in the CPC National Collection:
Rae Selling Berry Seed Bank & Plant Conservation Programs
The conservation of Silene douglasii var. oraria is fully sponsored.
Edward Guerrant, Ph.D. contributed to this Plant Profile.
Three varieties of Silene douglasii are currently recognized (Kephart et al. 1999). Silene douglasii var. douglasii is the most widespread and is found in southern British Columbia, Washington, Idaho, Montana, Utah, Nevada, northern California and eastern and southern Oregon. Silene douglaii var. oraria and var. rupinae are very limited in their distribution. Silene douglasii var. rupinae is limited to a few locations on open, rocky outcrops along the Columbia River Gorge in Oregon and Washington. Silene douglasii var. oraria, which is listed as Threatened in Oregon, is found only in three coastal prairie sites in Oregon which are separated by approximately 30 to 75 miles (50-120 km). It is not known whether these plants once had a more extensive distribution. As late as the 1880s, coastal prairie was found extensively along the Oregon coast for a distance of nearly 250 miles (400km) (Kephart and Paladino 1997). Human caused disturbances and habitat succession have effectively destroyed most of this important habitat type.
Distribution & Occurrence
Grassy meadows and rocky outcrops that are part of the coastal prairie habitat type located on steep bluffs, ledges, and slopes facing the Pacific Ocean. Associated species include Koeleria nitida, Festuca rubra, Delphinium menziesii, Castilleja litoralis, Clarkia amoena, Eriophyllum lanaturm, Senecio bolanderi, and Rhus diversiloba.
|3 known populations. The largest contains over 1000 individuals. The other two sites contain fewer than 100 individuals (Brown and Kephart 1999).|
Conservation, Ecology & Research
Plants begin to put on new growth in late March. Flowering begins in late April and early May. New seedlings can be observed by May (Kephart and Paladino 1997). Seedling recruitment for this species is very low. In one study, only 5%-8% of the seedlings survived one year. Plants exhibit high levels of inbreeding depression, which may be linked to low vigor and ultimately plant death (Brown and Kephart 1999). Flowers of Silene douglasii var. oraria are protandrous, meaning that the anthers mature and shed pollen before the stigmas mature. However, flowers vary considerably in the timing of pollen shed, and self-pollination appears to occur. Outcrossing is facilitated by pollen gathering halictid bees (Lasioglossum sp.) and syrphid flies, but according to recent studies, pollen transfer appears to be limiting the reproductive potential of this rare plant (Brown and Kephart 1999).
Silene douglasii var. oraria has fairly specific habitat requirements. Plants cannot tolerate much competition for light from other plants or a heavy litter layer. In an extensive demographic study, it was found that seedling and adult survivorship were greatest in an open, rocky habitat. However, the soil conditions in the rocky habitat are not ideal, and plants in the deeper soils of the grassy habitat were observed to be larger than those growing on rocky soil. Management activities should take these preferences into consideration. The encroachment of shrubs and trees should be minimized, and an effective method of reducing litter layer accumulations in grassy habitats should be developed (Kephart and Paladino 1997).
Competition from aggressive, weedy species (Meinke 1982).
Coastal development and deforestation leading to habitat degradation and fragmentation (Brown and Kephart 1999).
Habitat fragmentation leading to reduce
The three varieties of Silene douglasii (var. oraria, var. douglasii, and var. rupinae) were compared using a wide variety of morphological characteristics. Significant differences among varieties were found, reinforcing the categorization of the three varieties. Significant differences were also found within each of the three varieties, indicating geographic differences and population substructuring (Kephart et al. 1999).
Studies to determine the mating system and to quantify the magnitude of inbreeding depression were conducted. Flower treatments included emasculation (removal of pollen) followed by treatment with the plant's own pollen (self) or another plant's pollen (outcross), bagging (exclusion of pollinators), and open pollination. Silene douglasii var. oraria has a mixed mating system. It is capable of setting seed with its own pollen or pollen from another plant. Inbreeding depression was high compared to many outcrossing species (Kephart et al. 1999).
Studies of the pollination biology of Silene douglasii var. oraria. Natural pollen deposition was monitored. Fruit production, seed number and weight, and progeny vigor were studied for different pollination treatments (selfed, open pollinated, and different amounts of supplemental pollen). Overall, it appears that most natural pollen transfer involves self-pollination and low reproductive success reflects low pollen quantity and quality (Brown and Kephart 1999).
Germination trials at The Berry Botanic Garden indicate that this species germinates readily under a variety of conditions but that it does slightly better when subjected to cold stratification and constant temperatures. 100% of seeds germinated when subjected to 8 weeks of cold stratification followed by constant 68F (20C) and 80% germinated when cold stratification was followed by alternating 50F/68F (10/20C) temperatures. Without cold stratification, 80% of seeds germinated in the constant temperature treatment and 60% germinated under the alternating temperature treatment (BBG File).
Genetic studies using microsatellite DNA are currently underway (Kephart and Yee, unpublished in: Kephart et al. 1999).
The largest known population is on private land that is managed by The Nature Conservancy.
The two other known populations are on State Park land. This species is listed as threatened by the state of Oregon, so plants on state land are protected from destruction and development.
Re-introduction of more than 200 individuals grown in the greenhouse into formerly grazed habitat (in Brown and Kephart 1999).
Minimize the encroachment of shrubs (Kephart and Paladino 1997).
Develop an effective method of reducing litter accumulation and other cover in grassy habitats (Kephart and Paladino 1997).
Determine propagation and reintroduction protocols.
Cody, W.J. 1996. Flora of the Yukon Territory. Ottawa, Ontario: NRC Research Press. 643p.
Welsh, S.L. 1974. Anderson's Flora of Alaska and Adjacent Parts of Canada. 724p.