BC Conservation Data Centre: Species Summary
Scouleria marginata
margined streamside moss
| Scientific Name: | Scouleria marginata Britt. | ||||||||||
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| English Name: | margined streamside moss | ||||||||||
| Classification / Taxonomy | |||||||||||
| Scientific Name - Concept Reference: | Anderson, L.E., H.A. Crum, and W.R. Buck. 1990. List of the mosses of North America north of Mexico. The Bryologist 93(4):448-499. | ||||||||||
| Classification Level: | Species | ||||||||||
| Species Group: | Bryophyte | ||||||||||
| Species Code: | SCOUMAR | ||||||||||
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| Conservation Status / Legal Designation | |||||||||||
| Global Status: | G3 (Mar 2025) | ||||||||||
| Provincial Status: | SH (Apr 2024) | ||||||||||
| BC List: | Red | ||||||||||
| Provincial FRPA list: | |||||||||||
| Provincial Wildlife Act: | |||||||||||
| COSEWIC Status: | Endangered (May 2012) | ||||||||||
| SARA Schedule: | 1 - Endangered (Jan 2005) | ||||||||||
| General Status Canada: | |||||||||||
| Ecology & Life History | |||||||||||
| General Description: | |||||||||||
| Technical Description: | |||||||||||
| Identification Comments: | Plants 6-10 cm tall, perennial, erect, frequently branched, forming dark green, yellowish-brown to blackish sods. Leaves 2.5-4.0 mm long x 0.8-1.2 mm wide, lanceolate to lingulate, tapering to a rounded-obtuse to somewhat pointed apex, slightly contorted when dry and spreading when wet, margins weakly toothed to entire, multistratose. Midrib (costa) up to 140 micrometers wide, ending near the tip of the leaf. Median and upper leaf cells thick-walled, roughly isodiametric, 9-15 micrometres. Basal leaf cells adjacent to the costa usually short rectangular to rectangular, 12 to 17.5 micrometres X 7 to 10 micrometres, more thin-walled than upper cells. The small area of differentiated alar cells is comprised of quadrate to short-rectangular, thick-walled cells. At the leaf base above the alar region, a band of distinct, very thick-walled elongate sub-marginal cells is present. Dioicous, with female and male plants similar in appearance. Perigonial and perichaetial bracts similar to the vegetative leaves. Setae short, up to 2 mm long, erect. Capsules 2-2.5 mm in diameter, more or less spherical when wet and slightly flattened-spherical when dry, with a short-conic operculum. At maturity, the thick columella is exserted through the capsule mouth and remains attached to the operculum. Spores ca. 40 micrometres in diameter, lightly roughened (COSEWIC 2002x; Lea et al 2007). | ||||||||||
| Similar Species: | Scouleria aquatica is very similar and occurs in the same habitat, but has unistratose to occasionally bistratose areas in the margins, and peristome teeth. Partially bistratose specimens of S. aquatica have often been misidentified as S. marginata. The leaves of S. aquatica may be more contorted than S. marginata when dry. Scouleria marginata is usually indistinguishable from S. aquatica in the field, requiring a voucher specimen or field microscope to confirm identity, but on younger, non-eroded leaves the distinctly thickened and rounded leaf borders of S. marginata may be readily evident with a 20X hand lens. The leaves of S. marginata may also be blacker and narrower than those of S. aquatica. Scouleria marginata also exhibits a tendency to develop yellowish or golden hues not seen in S. aquatica (COSEWIC 2002x; Lea et al 2006). | ||||||||||
| Global Reproduction Comments: | Spores are likely dispersed by water, or (possibly) by wind (COSEWIC 2002). | ||||||||||
| Provincial Reproduction Comments: | Scouleria marginata is dioicous, with female and male plants similar in appearance. This species produces sporophytes and spores occasionally to infrequently across its range. This probably reflects its dioicous condition (male and female reproductive units on separate plants), which appears to restrict sporophyte production in many moss species. The BC collection has sporophytes. Spores are probably dispersed by water or, possibly, wind. There is no information on spore dispersal distances, viability, or germination success with regard to this species. Also, there is no evidence of asexual reproduction by specialized propagules or fragmentation by Scouleria marginata, although the lower leaves are often stripped or greatly eroded in habitat, and these fragments presumably act as sources for vegetative dispersal. (COSEWIC 2002x; Lea et al 2006). | ||||||||||
| Global Ecology Comments: | Mosses in this genus have extremely strong rhizomes that allow the plant to withstand flood events (WNHP 2025). | ||||||||||
| Provincial Ecology Comments: | Specific information on the ecology of Scouleria marginata is not available. The closely related Scouleria aquatica appears to have the same ecological preferences as S. marginata and may outcompete it for space, thus partly accounting for the restricted range of S. marginata (Lea et al 2006). | ||||||||||
| Habitats: (Type / Subtype / Dependence) |
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| Global Habitat Comments: | As with other species of Scouleria, Scouleria marginata occurs in or beside streams, attached to rocks and either floating or exposed in low water (Lawton 1971). More specifically, it is found on rocks, particularly of granitic or volcanic composition, in the splash zone of streams or rivers from 1,000 to 1,800 m in elevation (FNA 2007, WNHP 2025). Associated species include Scouleria aquatica, Racomitrium aciculare, Schistidium rivulare, and Scleropodium obtusifolium (British Columbia Conservation Data Centre 2025). | ||||||||||
| Provincial Habitat Comments: | Little information is available for habitat of Scouleria marginata in BC. It appears to be restricted to wet rocks and/ or outcrops along seasonally flooded streams in montane areas. At the only reported location for this species in BC (Boundary Creek), it occurred on a rock along a creek margin at about 1300 m elevation (Tan 1980). Fieldwork in 2001 indicated that the headwater of Boundary Creek is partially open and surrounded by montane riparian forest. Habitat around Boundary Creek has changed markedly since Tan collected there in 1977. A forest fire burned the site in the late 1980s or early 1990s and flooding deposited a deep layer of sediment around the lake and into Boundary Creek for at least 1 km. Fallen trees are present in the creek and cattle graze the area along the stream and lake margins. Few rocks or boulders remain around the lake and the few that remain exposed in Boundary Creek are mostly bare of mosses (COSEWIC 2002x). | ||||||||||
| Provincial Phenology: (1st half of month/ 2nd half of month) |
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| Provincial Phenology Comments: | Information on the phenology of Scouleria marginata is not available. Scouleria produces sporophytes during the winter and sheds spores in summer when lowered streamflows enable capsules to dry out, shrink, and release spores. When rewetted, the capsules swell and close, preventing the release of spores. Spore dispersal presumably occurs by both wind and water (J. Christy, pers. comm. 2008). | ||||||||||
| Elevation (m) (min / max): | Provincial: 1310 / 1310 | ||||||||||
| Known Pests: | |||||||||||
| Pollen Vector: | |||||||||||
| Pollinator: | |||||||||||
| Dispersal: |
ABIOTIC
Water |
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| Provincial Inventory | |||||||||||
| Inventory Priority: | A - Highest | ||||||||||
| Ownership of occurrences (Known locations): | Mostly national government | ||||||||||
| Inventory Need: | Search the previously known site to relocate any existing populations. Conduct an intensive survey of seasonally flooded streams in the Boundary Creek area (Lea et al 2006). | ||||||||||
| Inventory Comments: | Scouleria marginata appears to have been extirpated from its original collection site at Boundary Lake (Tan 1980). When revising the genus Scouleria, Churchill (1985) examined hundreds of specimens, including those at the University of British Columbia, without discovering any new Canadian records of S. marginata that might have been misidentified as S. aquatica. In 2001, T. McIntosh followed personal directions from Tan to search the area around Boundary Lake and portions of Boundary Creek near its outflow, but found no new populations. Poor road conditions precluded access to portions of Boundary Creek towards the American border. At the same time, McIntosh sampled other potential and accessible sites of similar habitat within an approximately 20 km radius, including small creeks that feed into Boundary Lake. In most cases the sites had an abundance of moss-covered rocks in and beside the water and patches of Scouleria aquatica were present. Other waterways were sampled along Highway 3 north of Boundary Lake, including Monk Creek, Buckworth Creek, Maryland Creek, Summit Creek, and Blazed Creek. In all cases, only S. aquatica was found on wet rocks at these sites, where it was occasional but never abundant. McIntosh searched the Boundary Lake area again in 2005 and inventoried the west end of the lake, including a few small unnamed tributaries, and about 15 km of Boundary Creek east of the lake, from the American border westwards. Although the rocks in these areas often had much richer moss communities than adjacent to Boundary Lake, and Scouleria aquatica was relatively common, none of the 55 patches that were sampled were S. marginata. However, given the dozens of streams in the area, many of which are fairly inaccessible, it is certainly possible that S. marginata still exists in the region (COSEWIC 2002x; McIntosh 2006b; Lea et al 2006). | ||||||||||
| Economic Attributes | |||||||||||
| Provincial Economic Comments: | No commercial or cultural uses are known for Scouleria marginata. | ||||||||||
| Distribution | |||||||||||
| Endemic: | N | ||||||||||
| Global Range Comment: | Scouleria marginata occurs in western North America, from Washington to Montana, Oregon, and California in the United States (FNA 2007). It was known from a single herbarium collection from 1977 found in British Columbia in the Kootenay Region near the Canadian/American border, which is now considered historical (Ireland et al. 1987, COSEWIC 2002, NatureServe 2025). Range extent was estimated using herbarium specimens and NatureServe Network occurrence data collected between 1994 and 2025 (RARECAT 2024, GBIF 2025, NatureServe 2025, SEINet 2025). | ||||||||||
| Disjunct, more common elsewhere: | N | ||||||||||
| Peripheral, major distribution elsewhere: | Y | ||||||||||
| Authors / Contributors | |||||||||||
| Global Information Author: | N. Ventrella (2025) | ||||||||||
| Last Updated: | Mar 17, 2025 | ||||||||||
| Provincial Information Author: | Christy, John A. | ||||||||||
| Last Updated: | Mar 20, 2008 | ||||||||||
| Last Literature Search: | |||||||||||
| References and Related Literature | |||||||||||
B.C. Ministry of Environment. Recovery Planning in BC. B.C. Minist. Environ. Victoria, BC. |
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British Columbia Bryophyte Recovery Team. 2007d. Recovery strategy for the margined streamside moss (Scouleria marginata Britt) in British Columbia. Prepared for the B.C. Ministry of Environment, Victoria, BC. 14pp. |
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British Columbia Conservation Data Centre. 2025. Species Summary: Scouleria marginata. B.C. Ministry of Environment, Victoria. Online. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed 17 Mar 2025). |
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Christy, J.A. and D.H. Wagner. 1996. Guide for the identification of rare, threatened or sensitive bryophytes in the range of the northern spotted owl, western Washington, western Oregon, and northwestern California. USDI Bureau of Land Management. 200 pp. |
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Churchill, S.P. 1985. The systematics and biogeography of Scouleria Hook. (Musci: Scouleriaceae). Lindbergia 11: 59-71. |
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COSEWIC 2002. COSEWIC assessment and status report on the margined streamside moss Scouleria marginata in Canada. Committee on the Status of Endangered Wildlife in Canada, Ottawa. vi + 14 pp. |
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COSEWIC. 2002x. COSEWIC assessment and status report on the margined streamside moss Scouleria marginata in Canada. Comm. on the Status of Endangered Wildl. in Can. Ottawa. vi + 14 pp. |
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Flora of North America Editorial Committee (FNA). 2007b. Flora of North America north of Mexico. Vol. 27. Bryophytes: Mosses, Part 1. Oxford University Press, New York. xxi + 713 pp. |
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Lawton, E. 1971. Moss Flora of the Pacific Northwest. The Hattori Botanical Laboratory, Nichinan, Miyazaki, Japan. |
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McIntosh, T.T. 2006b. Search effort (field inventories) for Scouleria marginata (the margined streamside moss) and Fabronia pusilla (the silver-hair moss). Biospherics Environmental. Vancouver, BC. 2 pp. |
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Tan, B.C. 1980. A moss flora of Selkirk and Purcell Mountain Ranges, southeastern British Columbia. Ph.D. Thesis, Univ. of B.C., Vancouver. |
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Washington Natural Heritage Program (WNHP). 2025. Online Field Guide to the Rare Plants of Washington. Online. Available: https://fieldguide.mt.gov/wa (accessed 2025). |
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Please visit the website Conservation Status Ranks for definitions of the data fields used in this summary report.
Suggested Citation:
B.C. Conservation Data Centre. 2025. Species Summary: Scouleria marginata. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 13, 2026).