Pygmy pocket moss (Fissidens exilis) COSEWIC assessment and status report: chapter 4

Distribution

Global range

Fissidens exilis is known from the British Isles, central and northern Europe, Scandinavia (Steere 1950), and Japan (Iwatsuki & Noguchi 1973). It also occurs in New Zealand, where it is thought to have been introduced (Beever 1999). NatureServe (2005) reports that it is also found in Algeria and South America. In North America, the distribution of F. exilis appears to reflect that of a large number of eastern deciduous forest species (e.g. Argus & Pryer 1990). In Europe, F. exilis occupies much higher latitudes than are attained by the species in North America.

The first discovery of Fissidens exilis in North America was made in 1947, in Cleveland, Ohio (Steere 1950), and since then it has been collected in ten other eastern United States (Crum & Anderson 1981, Missouri Botanical Garden 2002, New York Botanical Garden 2002)) and in two Canadian provinces (Ontario, Quebec) (Figure 2). That all North American populations have been discovered only within the last 55 years or so in a relatively well-botanized region is unexplained.

Figure 2. Approximate North American distribution of Fissidens exilis. Black diamonds indicate sites for which the co-ordinates of the population are known. Open diamonds show states for which F. exilis is known but for which no exact co-ordinates are given in on-line records (Missouri Botanical Garden 2002, New York Botanical Garden 2002).

Figure 2. Approximate North American distribution of Fissidens exilis.

Canadian range

In Canada, Fissidens exilis has been collected from Essex (two localities), Kent, Waterloo, and Haldimand-Norfolk Counties in southern Ontario, and from two locales in Quebec: one in Gatineau Park, near the south end of the Ontario-Quebec border, and one in the city of Montréal (Appendix 1). The Montréal occurrence represented the first Canadian report (Molnar 1975), but no specimen supporting the claim has been found either at the McGill University McDonald Campus Herbarium (MTMG), where it was reportedly deposited (Molnar 1975) or at any of several major eastern North American herbaria. This may indicate that the specimen has been annotated, casting doubt on the occurrence record. The first Ontario record was reported by Oldham (1983).

Field work associated with this report in 2002 involved searching for minute Fissidens at over thirty sites in southern Ontario and Quebec that were visited for COSEWIC status reports on Bryoandersonia illecebra, Helodium paludosum, and Fissidens exilis. Samples were gathered from eleven sites, three of which were previously documented for Fissidens exilis. Fissidens was sought incidentally along site access routes and at sampling destinations at each site for a minimum of 1 hour and a maximum of five hours per site. Forty-six voucher collections were made. Of these, just one represented F. exilis. Most of the remaining samples represented F. taxifolius. This result after concerted search effort shows despite the small, inconspicuous aspect of F. exilis, undercollection does not fully account for the small number of Canadian records.

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