Management plan for Twisted Oak Moss in Canada [final] 2011: Species Information

Date of Assessment: May 2004
Common Name (population): Twisted Oak Moss
Scientific Name: Syntrichia laevipila Brid.
COSEWIC Status: Special Concern (met criterion for Threatened, D2, but designated Special Concern because of the high potential numbers of Garry Oak hosts).
Reason for Designation: This moss is a small species that occurs from British Columbia and Washington southward to California. The Canadian populations are at the northern limits of their range in western North America, and in Canada the species has a restricted distribution where it occurs in the area of south-eastern Vancouver Island and the Gulf Islands. The species is known from 25 sites where it is restricted to the bark of trees, in particular Garry oaks. This species is never dominant where it grows, nor is it frequent in large oak stands. Many of the known populations are in protected areas. The major threat to the species is the disappearance of mature Garry oaks, which would result in the extirpation of most populations of this species.
Canadian Occurrence: British Columbia
COSEWIC Status History: Designated Special Concern in May 2004. Assessment based on a new status report.

twisted oak moss^[1]

Legal Designation

• Identified Wildlife:^[2] No
• B.C. Wildlife Act: No
• SARA Schedule: 1 (2005)

Conservation Status^[3]

B.C. Rank: S2S3 (2007)
B.C. List: Blue
Global Rank: G3G4 (2009)

Subnational Ranks^[4]: Not assessed in CA or WA

B.C. Conservation Framework ^[5]

Goal 1: Contribute to global efforts for species and ecosystem conservation. Priority:^[6] 3
Goal 2: Prevent species and ecosystems from becoming at risk. Priority: 6 (2009)
Goal 3: Maintain the diversity of native species and ecosystems Priority: 2 (2009)

Action Groups: Compile Status Report; Send to COSEWIC; Planning; Habitat Protection; Habitat Restoration; Private Land Stewardship; Monitor Trends

¹Data Source: B.C. Conservation Data Centre (2010) unless otherwise noted

² Identified Wildlife under the Forest and Range Practices Act

³ S = Subnational; N = National; G = Global; B= Breeding; X = presumed extirpated; H = possibly extirpated; 1 = critically imperiled; 2 = imperiled; 3 = special concern, vulnerable to extirpation or extinction; 4 = apparently secure; 5 = demonstrably widespread, abundant, and secure; NA = not applicable; NR = unranked; U = unrankable

⁴ Data Source: NatureServe (2009)

⁵ Data Source: Ministry of Environment (2010)

⁶ Six-level scale: Priority 1 (highest priority) through to Priority 6 (lowest priority).

This description is based on COSEWIC (2004), Mischler (2007), and Lawton (1971). Twisted oak moss is a small moss that grows as tufts or patches of <1 cm² on the bark of trees, usually Garry oak (Quercus garryana). Its stems are usually <5 mm tall and its leaves rarely longer than 1.5 mm. The leaves are oblong and are twisted around the stem when dry, and spreading and slightly bent backwards when wet. Leaf margins are plain to sometimes weakly recurved in the middle of the leaf. In larger plants, leaf mid-ribs often extend beyond the leaf tip as smooth to toothed, clear hairpoints (Figure 1). Smaller plants are often characterized by a lack of hairpoints and the presence of small (~0.4 mm long), leaf-like gemmae (asexual reproductive structures) in the upper axils of the leaves (figure 2:). The middle and upper leaf cells of twisted oak moss are isodiametric (each side of the cell has the same dimensions) to short-rectangular and covered by papillae (small bumps). The basal leaf cells are elongate, smooth, and clear. Twisted oak moss has both male and female sex organs on the same plant, which aids in successful fertilization and subsequent production of sporophytes (structures that produce spores). The sporophytes are composed of long, cylindrical capsules (which produce the spores) on the ends of long setae (stalks).

Figure 1. Twisted oak moss plants showing hairpoints on leaves (~ x 15). Photograph by T. McIntosh

Figure 2. A patch of twisted oak moss showing plants with gemmae at tops of the stems and leaves without hairpoints (~ x 15). Photograph by W. Miles

Twisted oak moss has a widespread but scattered global distribution. It has been reported from North America, Chile, southern Europe, eastern Asia, Japan, South Africa, and, possibly, New Zealand and Australia (COSEWIC 2004). Its North American distribution closely follows the distribution of Garry oak ecosystems. It is found along portions of the south coast of British Columbia and inland through Washington and Oregon and into California (Figure 3:); this distribution does not follow that proposed by Mischler (2007), as he includes another, more widespread species of uncertain taxonomy, S. pagorum, within his description.

In Canada, twisted oak moss has a narrow distribution in southern coastal B.C. (Figure 4; Table 1). It is most common in the Victoria area, with populations in the municipalities of Oak Bay, Saanich, and Victoria (Miles 2001, COSEWIC 2004). Outside of the Victoria area, twisted oak moss has been found in scattered populations: Pedder Bay, west of Victoria; Duncan, north of Victoria: Galiano Island; Salt Spring Island; and Nanoose Hill (Notch Hill), north of Nanaimo. Total populations for twisted oak moss in B.C. is 27, with two new populations documents since the COSEWIC status report (Table 1). Most occurrences are represented by numerous small (<1 cm²) patches that are restricted to relatively small areas at each site.

Before 2001, this species had been observed only occasionally in B.C. A 2001 study focusing on the distribution of the form of this species that produces gemmae (Miles 2001) showed that twisted oak moss is relatively widespread in the Victoria area, although rather uncommon within this range. It was found on only about 5% of the hundreds of trees examined. During field work for the COSEWIC status report ( COSEWIC 2004), more than 400 Garry oaks in sites near Duncan and Nanaimo and on Salt Spring Island were examined and twisted oak moss was found on only three trees. COSEWIC (2004) lists 31 populations, but some populations have been combined based on the B.C. Conservation Data Centre and NatureServe separation criteria for populations to be at least 1 km from one another (NatureServe 2009). Because of financial constraints put on her study, Miles (2001) mainly looked for and collected the smaller plants without hairpoints on the leaves. Therefore, this species may be more common in the Victoria area than her survey showed. Monitoring of populations has not been initiated.

The B.C. populations of twisted oak moss probably represent less than 1% of its global distribution and abundance (there are no reported estimates of global distribution and abundance for this moss). The population trend for the species is not known.

Figure 3. North American distribution of twisted oak moss (the dot in B.C. represents all extant locations)

Figure 4. British Columbia distribution of twisted oak moss (the Victoria area set of dots represents multiple populations in Victoria, Langford, Esquimalt, Colwood, Oak Bay, and Saanich)

¹ Populations are separated by a distance of at least 1 km based on the NatureServe criteria, and land tenure park names represent different parks. Municipal parks are managed by municipal governments (Colwood, Esquimalt, Langford, North Saanich, Oak Bay, Saanich, and Victoria), whereas regional parks are part of the Capital Regional District (CRD) parks system.

² The number in parentheses is the approximate area of the population in m²; this usually includes other bryophytes and exposed bark.