CPC National Collection Plant Profile
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Silene douglasii var. oraria
Family: |
Caryophyllaceae |
Common Name: |
Cascade head catchfly |
Author: |
(M.E. Peck) C.L. Hitchc. & Maguire |
Growth Habit: |
Perennial |
CPC
Number: |
3994 |
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Primary
custodian for this plant in the CPC National Collection of Endangered
Plants is: |
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Edward Guerrant, Ph.D. contributed to this Plant Profile. |
Silene douglasii var. oraria
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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 |
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State Range
Habitat
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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. |
Distribution
Number Left
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3 known populations. The largest contains over 1000 individuals. The other two sites contain fewer than 100 individuals (Brown and Kephart 1999). |
State/Area
Protection
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State/Area |
Rank |
Status |
Date |
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Conservation,
Ecology & Research |
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Ecological
Relationships
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Silene douglasii var. oraria often produces many branches from just below the surface. This creates a compact cluster of leafy stems. Each stem can root, but they generally remain attached to the parent plant. Occasionally, a portion of the plant will die above ground, creating what looks like several individual plants growing in close proximity. This can make it difficult to correctly census the population, but careful mapping can make estimation possible (Kephart and Paladino 1997).
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). |
Threats
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• Heavy recreational use (Meinke 1982).
• 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 reduced gene flow and inbreeding depression (Brown and Kephart 1999).
• Two populations contain fewer than 100 individuals, placing them below accepted values for population viability (Kephart and Paladino 1997). In these two populations, reduced genetic variability and inbreeding may eventually lead to their extirpation.
• Grazing by deer, which reduces flower and fruit production (Brown and Kephart 1999). |
Current Research Summary
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• Long term (10 year) demographic monitoring of Silene douglasii var. oraria in two habitat types (grassy and rocky) at one site to aid in determining long-term population trends and habitat preferences. At the conclusion of the study, population growth appeared stable in the rocky sites and slightly declining in the grassy. Plants growing in the grassy habitat were more sparse but larger than plants growing in the rocky habitat. There was more seedling recruitment and adult survivorship in the open, rocky sites (Kephart and Paladino 1997).
• 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 68°F (20°C) and 80% germinated when cold stratification was followed by alternating 50°F/68°F (10°/20°C) 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). |
Current Management Summary
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• Seeds from two occurrences are currently stored at The Berry Botanic Garden.
• 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). |
Research Management Needs
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• Fence plants to limit herbivory and trampling. This will help maintain adequate numbers of flowering plants to help reduce inbreeding depression (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). |
Ex Situ Needs
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• Collect and store seeds from all known populations.
• Determine propagation and reintroduction protocols. |
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Books (Single Authors)
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Cody, W.J. 1996. Flora of the Yukon Territory. Ottawa, Ontario: NRC Research Press. 643p.
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Meinke, R.J. 1982. Threatened and Endangered Vascular Plants of Oregon: An Illustrated Guide. Portland, Oregon: U.S. Fish & Wildlife Service, Region 1. 326p.
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ONHP. 2001. Rare, Threatened and Endangered Plants and Animals of Oregon.
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Scoggan, H.J. 1978. The Flora of Canada. National Museums of CA, Publications in Botany.
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Welsh, S.L. 1974. Anderson's Flora of Alaska and Adjacent Parts of Canada. 724p.
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Books (Edited Volumes)
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James C. Hickman, Editor. 1993 The Jepson manual: Higher plants of California. Berkeley: University of California Press. 1400p.
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Electronic Sources
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ONHDB. (2000). Oregon Natural Heritage Program Database. Portland, Oregon.
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Journal Articles
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1947. (Original Publication). Univ. of Wash. Pub. Biol. 13: 40.
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Brown, E.; Kephart, S. 1999. Variability in pollen load: Implications for reproduction and seedling vigor in a rare plant, Silene douglasii var. oraria. International Journal of Plant Science. 160, 6: 1145-1152.
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Hultén, E. 1968. A Manual of the Vascular Plants. Flora of Alaska and Neighboring Territories. 1008 pp.
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Kephart, S.; Sturgeon, K.; Lum, J.; Bledsoe, K. 1999. Varietal relationships in Silene douglasii (Caryophyllaceae): Morphological variability at the population level. Systematic Botany. 24, 4: 529-544.
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Kephart, S.R.; Brown, E.; Hall, J. 1999. Inbreeding depression and partial selfing: evolutionary implications of mixed-mating in a coastal endemic, Silene douglasii var. oraria (Caryophyllaceae). Heredity. 82: 543-554.
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Kephart, S.R.; Christy, P. 1997. Demographic change and microhabitat variability in a grassland endemic, Silene douglasii var. oraria (Caryophyllaceae). American Journal of Botany. 84: 179-189.
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USFWS. 1976. Proposed Endangered Status for 1700 U.S. Plants. Federal Register. 41: 24523-24572.
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This
profile was updated on 7/8/2010 |
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