Twisted oak moss (Syntrichia laevipila) COSEWIC assessment and status report: chapter 4
Distribution
Global range
Syntrichia laevipila has a widespread but scattered global distribution: southern South America, Europe, Asia, North Africa, and western North America (Harpel 1997, Smith 1989; specimens from Australia and New Zealand identified as S. laevipila in the Herbarium at the University of British Columbia do not appear to be this species; further examination is required in order to confirm its presence in these areas). The global range of this taxon will probably change following a detailed taxonomic review of this species.
In North America, the distribution of Syntrichia laevipila basically follows the western distribution of the Garry oak ecosystem: it is found along the coast in British Columbia southwards and inland through Washington and Oregon and into California (Fig. 3). Harpel (1997) collected Syntrichia laevipila var. laevipila six times and S. laevipila var. meridionalis eight times from various locations on the western side of the San Juan Islands, less than 20km from known sites in British Columbia. It appears to be more common than previously thought In Oregon (Merrifield 2000).
Figure 3. North American distribution of Syntrichia laevipila.
NatureServe Explorer 2002 lists the range of Syntrichia laevipila var. laevipila (under Tortula laevipila) as frequent through most of Britain and Ireland, but rare in North Scotland; it is also listed from continental Europe, West, Central and East Asia, Algeria, Morocco, the Canaries and Azores, North America, southern South America, and Australia.
Canadian range
Syntrichia laevipila has a relatively narrow distribution in coastal British Columbia, restricted to Garry oak habitats from southern Vancouver Island northwards to the Nanaimo area on Vancouver Island (Fig. 4). It is most common in the Victoria area, with multiple populations at a number of sites, including Oak Bay, Saanich and North Saanich, Beacon Hill, and Mount Tolmie (see Table 1 for a listing of known populations and sites). Outside of Victoria, it becomes uncommon, found in a few scattered sites from Pedder Bay, west of Victoria, and northwards to the Nanaimo area. It has also been reported from two of the Gulf Islands, Salt Spring Island and Galiano Island. However, the twisted oak moss, although widespread in the Victoria area, is never a dominant species on the bark of Garry oak, nor is it common in large stands of oaks. Ryan (1996) listed it as present in the Queen Charlotte Islands, but this population has since been shown to be a misidentification.
In 2001, a study on the distribution and status of Syntrichia laevipila var. meridionalis was initiated in Victoria by W. Miles (sponsored by the BC Conservation Data Center; Miles 2001). Her study was thorough, yet focused only on the one variety of this species. She did not look for or collect S. laevipila var. laevipila, except unintentionally a few times. She showed that this variety is relatively widespread within the Garry oak ecosystem of coastal British Columbia (fieldwork for this Status Report has revealed that Syntrichia laevipila var. meridionalis appears to be the more common of the two varieties in Canada).
Miles surveyed about 1200 Garry oak trees across its range on Vancouver Island and on the Gulf Islands. She found the twisted oak moss on 66 oak trees, therefore on about 5 percent of the trees that were examined. She also examined about 20 trees of other species, mostly big-leaf maple (Acer macrophyllum), but only found it once (on maple; Population 39). In addition to examination of known populations in the Victoria area, T. McIntosh examined about 400 oaks in addition to those examined by Miles; these trees are mainly near Duncan, Nanaimo, and on Salt Spring Island at the apparent periphery of this moss’ range. It was found on three of these oak trees. Other tree species in open sites, especially big-leaf maple, were also surveyed, but not with the intensity of Garry oaks, and Syntrichia laevipila was not found.
During fieldwork, the presence of Syntrichia laevipila was confirmed at 25 sites, many of which, as noted earlier, are clustered in the Victoria area. Garry oak habitats north of Victoria were also searched, but it was confirmed only from Salt Spring Island.
Figure 4. Canadian distribution of Syntrichia laevipila.
