Flooded jellyskin (Leptogium rivulare) COSEWIC assessment and status report: chapter 4

Distribution

Global range

Eastern North America and western Europe; possibly eastern Eurasia (Goward et al. 1998). Defined by isolated and sometimes very old collections (1800s) in Sweden, Finland, Estonia, and France, and in the United States by very old specimens from Illinois and Vermont. The species appears to be genuinely rare in eastern North America. According to Dr Irwin Brodo (pers. comm., 2003), “I wrote to the curators of the large lichen herbarium in Minnesota (MIN), New York Botanical Garden (NY) and Michigan State University (MSC) and all three curators reported no specimens of Leptogium rivulare, even under its synonymous names. That means that such excellent and experienced collectors as Clifford Wetmore, Richard Harris and Henry A. Imshaug never found the species in their extensive collection efforts in the Great Lakes Region. Wetmore covered Isle Royale (Michigan) and Minnesota, Harris has collected all over eastern North America, including throughout the Adirondack and Catskill Mountains, and Imshaug covered all parts of Michigan and parts of the Lake Superior shore, all of them regions where the species might have been expected to occur judging by its known localities.”

Detailed European and American localities are given by Sierk (1964) and Jørgensen & James (1983), with additions in Jørgensen (1994). A world map can be found in Jørgensen (1994).

Figure 2. Distribution of L. rivulare in North America and Canada showing historical records more than 50 years old (solid squares), the record from 1965 that probably cannot be re-examined (open square), and extant populations (solid circles).

Figure 2. Distribution of L. rivulare in North America and Canadashowing historical records more than 50 years old (solid squares), the record from 1965 that probably cannot be re-examined (open square), and extant populations (solid circles).

Canadian range

Within Canada, Leptogium rivulare is known only from Ontario and Manitoba (Figure 2). It has been found in six places, five of them in Ontario and one in Manitoba (discovered after this report was originally submitted). It was formerly known from just three of these localities, each hundreds of kilometers from the next, and known only from herbarium specimen notations:

Carleton County (Ottawa Region): on base of Fraxinus in swamp, 10 Oct. 1971, I.M. Brodo no. 18746 (with F. Brodo and H.L. Dickson); determined by P.M. Jørgensen (CANL!)

Algoma District: Wawa, near "washout" on Magpie River, on base (partly flooded in spring) of Fraxinus nigra, 24 June 1965, Fabius LeBlanc, no. 1-7; determined by I.M. Brodo (CANL!)

Nipissing District: Lake Temagami, ‘Long Point,” on base of ash tree at edge of pond, 13 Aug. 1946, R.F. Cain, no. 21688, determined by G. Degelius (TRTC!)

A very recently collected specimen from Manitoba is in the process of being accessioned by the Canadian Museum of Nature. It was found on rock on a stony lakeshore near Flin Flon, together with other semi-aquatic lichens.

In connection with this report, the lichen has been relocated at the first of the above places (Ottawa), and found in two additional localities (indicated by asterisks, below) in Ontario 35 and 50 km to the west of the original location. The Ontario sites are listed below.

  • Ottawa (formerly Carleton County, or the Regional Municipality of Ottawa Carleton). The lichen is now known to occur in a cluster of six seasonal ponds and swamps. This population was well established and viable as of February, 2003.
  • *Lanark County, Darling Township: On trees in a cluster of seven seasonal ponds at the south end of White Lake. Discovered by Robert Lee in April 2001. Population well established and viable in April 2003.
  • *Lanark County, Pakenham Township. A very small, anomalous population on a few rocks in a high-energy flow streambed (Indian Creek). Possibly the result of an accidental introduction in 1994. Discovered by Robert Lee in August, 2002.

For the three currently known locations in Ontario, the extent of occurrence is approximately 130 km². Inclusion of the site in Manitoba increases this area to 107,000 km². The area occupied by suitable habitat for all four sites would be in the order of 2 or 3 hectares (0.2-0.3 km²). The total area of substrate (mainly tree bark) occupied by the lichen is about 40 (Appendix 1).

Consultation with Parks Canada (R. Alvo, S. Frey, D. Masse, E. Meleg, A. Promaine, and K. Wade) has failed to turn up any record of Leptogium rivulare in National Parks from La Mauricie in Québec, to Riding Mountain in Manitoba. All these informants agree, however, that lichens have hardly been studied, if at all, in these parks.

With only a few known occurrences well within a potentially broader Canadian range (suggested by the Vermont and Manitoba records to the east and west), it is not possible to say anything about changes in range. However, given the paucity of records across time (two centuries) and space (two continents), the lichen has evidently always been rare throughout its range. In Europe, it is listed as endangered in the Red List of Lichens of Estonia, and as regionally extinct in Finland (Randlane 1998; ArtDatabanken SoknigRodlista, Rödlistade arter i Sverige 2000; and Government of Finland 2000). In the United States and in Canada, the old collection sites (from 1858 to 1965) do not appear to have been revisited in recent times. The locations were simply too vaguely recorded, too many years ago.

Apart from the six currently known and historical localities, this lichen has apparently not been found elsewhere in Canada. With respect to seasonally flooded forests (an unusual habitat preference), it seems possible that it has been overlooked by lichenologists, who perhaps do not frequent such places (as suggested by Jørgensen & James, 1983). Indeed, in the National Herbarium (CANL) there are only six specimens from this specific habitat, five of them very old, of the crustose lichen Lecania cyrtella (Ach.) Th. Fr., which has been seen to be abundant and frequently intermixed with L. rivulare on tree bases in the ponds currently under study (no Leptogium rivulare was inadvertently included in this material).

Rocky streambeds and lakeshores, however, while they may seem to be anomalous environments for Leptogium rivulare, are the normal habitat of other semi-aquatic lichens, and these places have been given proper attention. Two species that have occurred on rock with L. rivulare are the foliose Dermatocarpon luridum (With.) J.R. Laundon, and the crustose Staurothele fissa (Taylor) Zwackh. There are about 100 specimens of these two species from streams and lakes in the National Herbarium. Most (84) of these were fairly evenly distributed across those parts of the country that include the core of the Canadian range of L. rivulare, from the Ottawa region in eastern Ontario westward to Thunder Bay. Other collections of these associated lichens have been made outside the known range, to the west in Alberta, north beyond Flin Flon, Manitoba, and to the east in Quebec and New Brunswick. (No L. rivulare was inadvertently included in any of these collections, 25 of which are on the original substrate.)

At the very least, it can be said that at 100 rocky shoreline sites across the country, lichenologists have collected other lichens from the right substrate in suitable habitat without Leptogium rivulare ever coming to light. Six of these were made by R.F. Cain, who first found L. rivulare in Canada, and he did not find it on those rocks, but only on the base of a tree in a pond, as previously described.

Could it have been missed? Perhaps it could be, when very young or not well established. But although Leptogium rivulare is regarded as a small species in its genus, it is a macrolichen and it is almost the only foliose lichen in these environments. It is distinctively coloured, and when it grows in large patches, it can be seen 10 metres away and recognized on sight.

In a broader context, general lichenological work has also failed to turn up any specimens of Leptogium rivulare in Ontario or adjacent parts of Quebec. It was not found in the 1860s by any of several collectors, including John Macoun, who, according to Wong and Brodo (1973) worked along the St. Lawrence River or the north shore of Lake Ontario. More recently, P.-Y. Wong has made a concerted effort over several decades to collect all across southern Ontario, an area that includes all of the locations known up to the time of this report’s original submission (I.M. Brodo, personal communication 2003). Flooded habitats were not specifically targeted. In conjunction with that survey, Wong also consulted the herbarium collections at the Canadian Museum of Nature and the University of Toronto (Wong & Brodo 1992). Over a 35-year period, I.M. Brodo has made an even more comprehensive collecting effort within “the Ottawa District,” which is encompassed by a circle of 50 km radius centred on the city of Ottawa (Figure 3).

Figure 3. Distribution of L. rivulare (solid circles) in the eastern-most part of Ontario and some of the apparently suitable sites that are without L. rivulare (open circles) in relation to the 50-km radius of the “Ottawa district” covered by Brodo (1988).

Figure 3. Distribution of L. rivulare (solid circles) in the eastern-most part of Ontario and some of the apparently suitable sites that are without L. rivulare (open circles) in relation to the 50-km radius of the “Ottawa district” covered by Brodo (1988).

In consequence, in spite of its seeming abundance in a few ponds in eastern Ontario, Leptogium rivulare appears to have always been rare everywhere in its global range. Its restrictive dependence on a limited and unstable habitat may be one factor, but ineffective dispersal may be more important.

Distribution within the range appears to be quite restricted. Searching of much suitable habitat over a period of three decades by I.M. Brodo (pers. comm., 2002), and more recently by Robert Lee (see Figure 3 and Appendix 2), has shown that the currently known localities in Ontario are rather circumscribed, with the lichen being absent from all suitable habitat (about 40 sites) within one kilometer of the localities where it is known, and from another 20 places that are more distant (Upper Duck and Petrie Islands, 15 and 25 km to the east of Ottawa; at Chelsea, Québec, 30 km to the north; along the middle reaches of the Noire River, Québec, 160 km northwest of Ottawa; and at Anima Nipissing Lake, 20 km north of Lake Temagami in Ontario). The extent of the population near Flin Flon, Manitoba is not known.

To determine if it might still have been underreported, Robert Lee searched specifically for it at more than 60 sites during the years 2001 and 2002, with efforts first being concentrated immediately around the known populations. All suitable habitats within about a kilometer of these populations were examined, with negative results showing that they are limited in extent. Secondly, almost all other patches of habitat that came to attention in the general region of these populations were searched. Thirdly, extensive areas of apparently suitable habitat (river floodplains) were sampled, in case Leptogium rivulare should turn out to be abundant within some major but neglected watershed. None was found.

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