Synonyms: Lichen rivulare Ach., Lich. Suec. Prodr. 131 (1798); type: Sweden (H-Ach 1915B, lectotype designated by Jørgensen & James ).
Leptogium crenatellum Tuck. Amer. J. Arts Sci., ser. 2, 28: 200 (1859); type: USA, Vermont, Brattleboro, Frost (FH, holotype; US, isotype).
Leptogium sernanderi Du Rietz, Bot. Notiser 1922: 318 (1922); type: Sweden, Uppland, Knivsta, Noorsån, 27 July 1917, G. Sernander (UPS, lectotype designated by Jørgensen & James ; isolectotypes distributed in Malme, Lich. Suec., no. 851).
Leptogium rivulare is a globally rare lichen with very restrictive habitat requirements (the periodically inundated substrate, bases of trees or rocks). Potential habitats are easily diminished or even eliminated by natural processes (e.g. interference with the extent or duration of spring flooding) or the deterioration of habitats may be caused by human activities.
The taxon has only a few rich populations of stable condition worldwide (in Republics of Marii El and Komi, Russia, and in Ontario, Canada). In most documented locations it is represented by single or few thalli although suitable substrate is present and careful searching for the species has been performed. In 6 historical locations (Canada, Estonia, Finland, and USA) the taxon is considered extinct.
A criterion: Information about population reduction is based on the records of the species – altogether 30 locations in Europe and North America are documented, of these 6 are considered extinct (single localities in Estonia and Finland, populations in Illinois and Vermont in USA, and two populations in Ontario, Canada). According to A2, population size reduction is estimated 20%, i.e. less than 30%; thus the species does not qualify for VU, but is close to it, qualifying for NT.
B criterium does not apply as EOO is wider than 20 000 km2, number of known locations is over 10 and the species is not severely fragmented.
C and D criteria are not applicable as relevant numbers of individuals are not available. E criterium is not applicable as no quantitative analyses have been carried out.
Decision: Leptogium rivulare is assessed NT for the global Red List.
The species occurs in the Northern Hemisphere, in eastern North America and scattered in Europe, altogether in 10 countries.
EUROPE: Belarus - one location in Gomel region (Motiejūnaitė & Golubkov 2005); Estonia - one location, recorded in 1957 (Randlane 1987), CR according to the official Red List of Estonia (2008), actually should be considered extinct; Finland – in Lapponia kittilensis, extinct (Santesson et al. 2004); France (Roux 2012); Lithuania - one location in Zarasai district (Motiejūnaitė et al. 2011); Portugal (Boom & Jansen 2002); Russia – Republic of Komi, 30 separate observations in 9 locations (Pystina et al. 1999; Red Data Book of the Republic Komi 2009), Republic of Marii El, 15 separate observations (Bogdanov & Urbanavichus 2008), northern and middle parts of Ural Mts. (Urbanavichus 2010, Paukov & Teptina 2012), Murmansk region, former Kutsa Nature Reserve (Halonen 1996); Sweden – in Östergötland, Södermanland, Uppland, Dalarna and Gästrikland (Santesson et al. 2004).
NORTH AMERICA: Canada – in Ontario, 3 extant localities with hundreds of observations and 2 localities probably extinct, and one extant population in Manitoba (COSEWIC 2004); USA – in Illinois and Vermont (both probably extinct according to COSEWIC 2004), and in Wisconsin (2012, according to CNALH).
Information about population reduction is based on the records of the species – altogether 30 localities in Europe and North America are documented, of these 6 locations are extinct (single localities in Estonia and Finland, populations in Illinois and Vermont in USA, and two further populations in Ontario, Canada).
It seems that the populations are more threatened in the European nordic countries (extinct in Finland and Estonia, EN in Sweden) while new records are from Belorus, Lithuania and Portugal (1 locality each). Russian populations, especially those from the Republic of Marii El, are evaluated as stable (Bogdanov & Urbanavichus 2008). In the Republic of Komi, there are 30 separate observations of which only 2 were evaluated as rich populations; all other records were of a few thalli (Pystina et al. 1999). In the Middle Urals the species is found as the only large specimen and no other findings were made so far although suitable substrate is abundant in this area and despite thorough search (Paukov & Teptina 2012; Paukov, pers. comm.).
In Canada, Leptogium rivulare is currently known in Manitoba, and in 3 localities in Ontario, where the populations are 15 to 35 km apart. In 2 of these localities, the lichen occurs almost exclusively on tree bases around seasonal ponds. It forms irregular growths on dozens to many hundreds of trees in these places. On some trees, it is barely present; on others, it forms large, encrusting patches about 50 cm across. The great numbers of small thalli often scattered over the bark indicate that successful reproduction is occuring, while the large patches show persistence over many years. Almost all individuals are fertile, and are capable of reproducing when only a few years old. The total amount of Leptogium rivulare in Ontario is assessed ca 40 m2 (COSEWIC 2004).
On the other hand, the region where the species is now found has been well studied by lichenologists, and careful searching of the full range of habitat possiblities in more than 60 sites, in the vicinity and region of the existing and historical populations, has failed to turn up any sign of it (COSEWIC 2004).
In summary, Leptogium rivulare is a globally rare lichen having only a few rich populations of stable condition (in Republics of Marii El and Komi, Russia, and in Ontario, Canada). But even in these countries it is redlisted – threatened in Canada, category 1 (endangered) in Komi and category 3 (rare) in Marii El Republics. In most documented locations it is represented by single or few thalli although suitable substrate is present and careful searching for the species has been performed. In 6 historical locations worldwide (Canada, Estonia, Finland, and USA) the taxon is considered extinct; however, most of the historical localities have not been revisited because of too vague locality data.
The species has very restricted habitat requirements, found primarily at the margins of seasonal (vernal) pools or small rivers, where it grows on rocks and at the base of living deciduous trees between seasonal high and low water marks. It is vulnerable to changes in normal patterns of annual flooding, as well as to death of host trees (COSEWIC 2004). It has been noticed that the species can survive on fallen trunks for 3 years, after this it would disappear (Bogdanov & Urbanavichus 2008). In nordic countries, the species inhabits partially inundated roots or bases of trees, particularly Alnus glutinosa and Populus tremula along rivers, or rocks (Jørgensen 2007). In Russia the species has been recorded on different phorophyte species (Alnus, Betula, Pinus, Populus, Quercus, Salix and Ulmus), but mainly on Populus tremula, in the area where water stays for a long time during springs (Hermannson & Kudryatseva 1995; Pystina et al. 1999; Bogdanov & Urbanavichus 2008). In Canada, the old and present collections are from coniferous and deciduous tree species (Abies, Acer, Cornus, Fraxinus, Quercus, Rhamnus, Salix, Thuja, Ulmus, and Vitis) in virtually identical habitats: the periodically inundated bases of trees, usually around the margins of basins that fill with meltwater each spring to form seasonal ponds (COSEWIC 2004).
Leptogium rivulare is vulnerable to changes in normal patterns of annual flooding, as well as to death of host trees. Restrictive dependence of this species on a limited and unstable habitat may be one threat factor as well as ineffective dispersal is another. It is suggested that the species can thrive only in unpolluted water streams (Paukov & Teptina 2012). Major threats to the largest populations in Canada include urban development and recreational activity.
In Russia some localities are from the protected areas, also the extant populations in Belorussia and Lithuania. Of the three localities currently known in Ontario, Canada, only one is in a way protected (COSEWIC 2004).
Bogdanov, G. A. & Urbanavichus, G. P. 2008. Lichen species new and rare to Russia from the Republic of Marii El. Botanicheskii Zhurnal (St. Petersburg) 93 (6): 944–950. (In Russian).
Boom, P. P. G. & Jansen, J. 2002. Lichens in the upper belt of the Serra da Estrela (Portugal). Österr. Z. Pilzk. 11: 1-28.
COSEWIC 2004. COSEWIC assessment and status report on the flooded jellyskin Leptogium rivulare in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 30 pp. (http://www.registrelep-sararegistry.gc.ca/virtual_sara/files/cosewic/sr_flooded_jellyskin_e.pdf).
Halonen, P. 1996. Lichens of the former Kutsa Nature Reserve. Oulanka Reports 16: 63–68.
Hermannson, J. & Kudryatseva, D. 1995. Notes on the lichens of the Pechoro-Ilych Zapovednik, Komi Republic, Russia. Graphis Scripta 7:67–78.
Jørgensen, P. M. 2007. Collemataceae. In: Nordic Lichen Flora 3: 31–42.
Motiejūnaitė, J., von Brackel, W., Stončius, D. & Preikša, Ž. 2011. Contribution to the Lithuanian flora of lichens and allied fungi. III. Botanica Lithuanica, 17(1): 39–46.
Motiejūnaitė, J. & Golubkov, V. V. 2005. Cyanolichens of freshwater aquatic and subaquatic habitats in Lithuania and Belarus. Botanica Lithuanica, 11(1): 35–40.
Paukov, A. & Teptina, A. 2012. New records of lichens from Middle Urals, Russia. Folia Cryptog. Estonica 49: 39–43. http://www.ut.ee/ial5/fce/fce49pdf/fce49_paukov.pdf
Pystina, T. N., Hermansson, J. & Kustysheva, A. A. 1999. New data on the distribution of a rare species Leptogium rivulare (Collemataceae, Lichenes). Botanicheskii Zhurnal (St. Petersburg) 84 (9): 126–131.
Randlane, T. 1987. Leptogium rivulare (Ach.) Mont. – a new rare lichen species in Estonia. Folia Cryptog. Estonica 25: 8–11.
Red Data Book of the Murmansk Region. Edition 2. / Eds. Konstantinova et al. - Kemerovo: Asia-Print Publishing. 2014. 584 pp. http://ias.kgilc.ru/redbook/?q=Lichens
Red Data Book of the Republic Komi. Rare and Endangered Species of Plants and Animals. Syktyvkar: Komi Republican Printing, 2009. 791 pр. http://ib.komisc.ru/add/rb/individuals/?id=2886
Red Data Book of the Republic Marij El. Plants and Fungi. Yoshkar-Ola: Mrijasky State University. 2013. 324 pp.
Roux, C. 2012. Liste des lichens et champignons lichénicoles de France. Bull. Soc. linn. Provence, n° spécial 16: 1–220.
Santesson, R., Moberg, R., Nordin, A., Tønsberg, T. & Vitikainen, O. 2004. Lichen-forming and lichenicolous fungi of Fennoscandia. Museum of Evolution, Uppsala University.
Urbanavichus, G. P. 2010. A checklist of the lichen flora of Russia. St. Petersburg. 194 pp. (In Russian).