Accessory fungi in lichenized systems


From 08/2005 to 08/2006

Principal Investigator: Gerhard Rambold
Staff: Derek Peršoh

Cryptic Lichenicolous Fungi

Cryptic lichenicolous fungi in the Letharietum vulpinae

Derek Peršoh


Lichenicolous fungi are fungi dwelling on or in lichens (Kirk et al. 2001). Today about 1000 species of obligate lichenicolous fungi are known. Most of them are visible to the naked eye on their host lichens (e.g. Phacopsis). However, a much wider range of fungi may be associated with lichens (Petrini et al. 1990, Girlanda et al. 1997, Caretta et al. 1998). They are mainly supposed to spread as sterile mycelia inside the lichens and are therefore not visible – mostly even not with optical devices. Therefore, we call them cryptic lichenicolous fungi.

The Letharietum vulpinae

The character species of the lichen community Letharietum vulpinae is Letharia vulpina, the wolf lichen. It grows on the bark of conifers (Central Europe, North Africa, North America) or on dead wood (Scandinavia, North America). Species of other fruticose (Bryoria, Evernia, Usnea) and foliose lichenised genera (Hypogymnia, Imshaugia, Melanelia, Parmeliopsis, Pseudevernia) accompany Letharia.

The sampling sites

Cryptic lichenicolous fungi were isolated from four sites in Europe and two in North America. Three of the former ones are located in the Alps at about 1900 m altitude: in the Nationalpark Berchtesgaden (Germany), at Turracher Höhe in Kärnten (Austria) and in Valle di Susa (Italy). The fourth European site is located in Sweden, near Sörvattnet. In California (USA), fungi were isolated in the James reserve (San Jacinto Mountains) and near the Sky Oaks field station.

Letharietum vulpinae on bark of Larix decidua

The sampling method (Peršoh 2002b)

The fungi were isolated in the field to reduce the number of possible contamination sources. The uppermost one mm of side branches of fruticose lichens - respectively a corresponding piece of the margin of foliose specimens - was transferred directly from the lichen (which was left attached to the tree) to the culture media, using sterile tweezers. Afterwards, the tweezers were used to drag the lichen fragment through the agar and tear it in smaller parts, which were spread over the whole plate. In the laboratory, the plates were examined regularly (daily within the first two weeks) and growing mycelia were transferred immediately to fresh media when detected. This way, from one lichen fragment up to 80 fungal strains could be isolated to pure culture.

Isolation of cryptic lichenicolous fungi under semi sterile conditions in the field

Sampling site in the Nationalpark Berchtesgaden

The cultures

The molecular analyses (Peršoh 2002b)

Most of the fungal strains do not sporolate under culture conditions. Therefore, we use molecular methods to classify the cryptic lichenicolous fungi. SSU and ITS nrDNA sequence data are gathered from the isolated strains. The SSU nrDNA sequences are aligned together with about 1000 fungal sequences obtained from GenBank. In most cases, phylogenetic analyses of the alignment make a classification of the fungi possible (e.g., assignment to a certain family). Analyses of the corresponding ITS nrDNA data allow us to further classify (e.g., assignment to a certain genus), or even identify the fungi.

The first results - fungi isolated from Usnea cf. subfloridana Stirt

First results were presented at the IMC7 in Oslo (Peršoh 2002b). From Usnea cf. subfloridana specimens at the three sampling sites in the European Alps 29 fungal strains were isolated. They were assigned to the following taxonomic groups by SSU nrDNA sequence analyses (numbers of isolates are given in brackets):

Basidiomycota (4)
Ascomycota (29)
Pezizomycotina (25)
(Chaetothyriomycetes) (4)
Dothideomycetes (7)
Pleosporales (1)
Eurotiomycetes (1)
Eurotiales (1)
(mitosporic) Trichocomaceae (1)
Lecanoromycetes (1)
Lecanorales (1)
Parmeliaceae (1)
Leotiomycetes (6)
Sordariomycetes (4)
Diaporthales (3)
Valsaceae (3)
Xylariales (1)
Xylariaceae (1)
Saccharomycotina (0)
Taphrinomycotina (0)

The isolated Ascomycetes were exclusively members of the Pezizomycotina. 19 of the 25 Pezizomycotina could be assigned to five certain classes, two isolates formed a sistergroup to a clade which included taxa of more than one class and four clustered at the base the Chaetothyriomycetes clade. As a result of the SSU nrDNA sequence analyses, the members of the Eurotiomycetes, Lecanoromycetes and Sordariomycetes could be assigned to certain families. The phylogenetic topology of the Dothideomycetes and Leotiomycetes is not in accordance with the current taxonomy of the groups and therefore most of these cultures these cannot be classified further.

An ITS nrDNA alignment, constructed in the context of a study of the phylogeny of the Xylariaceae, was used to identify one isolated fungus as Hypoxylon fuscum (Pers.) Fr.. The Valsaceaen strains were identified as Leucostoma curreyi (Nitschke) Défago. The two wood inhabiting species were probably present in the form of spores on the lichen. The Parmeliacean fungus belongs to the genus Usnea and is presumably a culture of the primary mycobiont. Primarily, we estimate interesting results from analyses of the ITS nrDNA alignments of the Dothideomycetes and Leotiomycetes, since they comprise many obligate lichenicolous fungi and the majority of the isolates.


  • Caretta G., Picco A.M., Valcuvia M., Guglielminetti M. Savino E. & G. Del Frate (1998). Mesophylic, thermophilic and keratinophylic fungi isolated from fruticose lichens of the genus Cladonia. - In: Sixth international mycological congress - IMC6 – Abstracts: 141. [Abstract from the sixth international mycological congress, held in Jerusalem, Israel, 23.-28. August 1998.]
  • Girlanda M., Isocrono D., Bianco C. & A. M. Luppi-Mosca (1997). Two foliose lichens as microfungal ecological niches. Mycologia 89: 531–536.
  • Kirk P.M., Cannon P.F. & J.C. David (2001). Ainsworth & Bisby's Dictionary of the Fungi, 9th Edition. CABI Bioscience.
  • Peršoh, D. (2002b). Screening for lichenicolous fungi of Usnea. In: Sevens international mycological congress – IMC7. [Abstract from the seventh international mycological congress, held in Oslo, Norway, 11.–17. August 2002.]
  • Petrini O., Hake U. & M.M. Dreyfuss (1990). An analysis of fungal communities isolated from fruticose lichens. Mycologia 82: 444–451.

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