|BOTANICAL ELECTRONIC NEWS|
|No. 506 July 28, firstname.lastname@example.org||Victoria, B.C.|
For over 140 years, lichens have been regarded as a symbiosis between a single fungus, usually an ascomycete, and a photosynthesizing partner. Other fungi have long been known to occur as occasional parasites or endophytes, but the one lichen-one fungus paradigm has seldom been questioned. Here we show that many common lichens are composed of the known ascomycete, the photosynthesizing partner, and, unexpectedly, specific basidiomycete yeasts. These yeasts are embedded in the cortex, and their abundance correlates with previously unexplained variations in phenotype. Basidiomycete lineages maintain close associations with specific lichen species over large geographical distances and have been found on six continents. The structurally important lichen cortex, long treated as a zone of differentiated ascomycete cells, appears to consistently contain two unrelated fungi, (Abstract from Spribille et al. 2016)
Edible Horsehair Lichen, Bryoria fremontii (also called Wila by Native People), has been an important food for Native People of the interior parts of British Columbia and Washington (Turner 1977, Crawford 2007). When lichenologists studied this species, they found that Inedible Horsehair Lichen, Bryoria tortuosa, has the same fungal and algal components as its edible counterpart, Bryoria fremontii. The DNA analysis also confirmed that both lichen species are formed of the same fungal element (ascomycete Bryoria) and have the same algal symbiont (green alga Trebouxia simplex). Formally, these two different lichens should be treated as a single species, in spite of the fact that one of them is edible and the other toxic due to the high content of vulpinic acid.
Toby Spribille and University of Montana microbiologist John P. McCutcheon were not satisfied with this solution. They analyzed DNA of both the edible Bryoria fremontii and the inedible Bryoria tortuosa and they confirmed already well known fact that both species had the same algal and fungal components (cf. Velmala et al. 2009). When they masked out the DNA of the algal and fungal common components from the DNA profile of the unedible Bryoria tortuosa, they saw DNA fragments that they identified as those of a basidiomycete yeast from the genus Cyphobasidium.
Eureka! While Bryoria fremontii is made up of only one fungal and one algal element with only occasional, scattered yeast cells present in the cortex, B. tortuosa has an abundance of the basidiomycete yeast Cyphobasidium growing in the lichen cortex.
Spribille and McCutcheon assembled a large team of scientists who tested many other fruticose and foliose lichens. They found that basidiomycete yeasts were present in many of the species they examined (Spribille et al. 2016).
Their discovery redefines our understanding of lichens although there are still many questions to be answered about the role the three components play in the life of lichens such as Bryoria tortuosa. The role of algae (or cyanobacteria in many other cases) is clear, but the action and interaction of the third fungal component has yet to be established. This new look at lichens would not have been possible without the discovery Toby Spribille et al. made. Congratulations to all of them!
[Editorial Note to the Plate, Figure 1: Dr. Viktoria Wagner, Toby Spribille's partner, is an accomplished plant ecologist working at the Masaryk University in Brno, Czech Republic.]
For more on this discovery see http://www.cbc.ca/news/technology/lichen-yeast-1.3689468
From: Tønsberg, T., & Goward, T. (2016). Cliostomum spribillei (Ramalinaceae, lichenized Ascomycetes), a new species from western North America. North American Fungi, 11(1), 1-7. http://pnwfungi.org/index.php/pnwfungi/article/view/1467
Cliostomum spribillei Goward & Tønsberg is described as new to science from Canada (British Columbia) and the U.S.A. (Idaho, Oregon and Washington) where it is corticolous on conifers in oldgrowth coniferous forests at high altitudes. It is easily distinguished from other Cliostomum species by its yellow, granular-sorediate thallus and production of usnic acid alone.
Cliostomum spribillei is named in honour of our friend and colleague Toby Spribille (born 1975) for his many significant contributions to our knowledge of northwest North American lichens.
Cliostomum spribillei is a species of old growth coniferous forests where it occurs on trunks and branches of conifers, mainly Abies lasiocarpa (including A. bifolia), but also Abies amabilis, Picea engelmannii, Thuja plicata, and Tsuga heterophylla. Long term studies of its ecological behavior in and near the type locality suggest a strong association with the rain-sheltered trunks and branches of Abies lasiocarpa in old growth conifer forests at subalpine elevations between about 1400 m and 1900 m. Here it appears to be further restricted to localities subject to frequent fog. Repeated searches for this species in habitats outside the montane fog belt have proved unsuccessful. Further work is needed to determine if these observations hold across its range.
The following old mnemonics does not work anymore:
"Alice Algae took a Lichen to Freddie Fungus and now they live together in a natural relationship."
Roger Rosentreter suggested a new one. I thought BEN readers should know… Adolf Ceska
Times are tough out in Nature these days
Housing costs and utility bills are up
So Freddy Fungus and Alice Algae decided it was best to get a roommate.
So the cellist, Yo-Yo (Ma) yeast moved in.
With some great music, harmony and a bit of genetics,
The three Freddy, Alice and Yo-Yo made music together.
Yo-Yo has them covered on the outside,
Alice brings in the groceries, and
Freddy holds them all together.
Added July 29, 2016
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