Tremella rhizocarpicola sp . nov . and other interesting lichenicolous Tremellales and Filobasidiales in the Nordic countries

New data on the diversity and geographical distribution of lichenicolous Tremellales and Filobasidiales in the Nordic countries is presented. One new species, Tremella rhizocarpicola, is formally described. Tremella pertusariae and T. protoparmeliae are reported as new to the Nordic countries, Syzygospora physciacearum is new to Iceland, Tremella rinodinae is new to Sweden, and T. caloplacae is new to Norway. Nine species are reported as new to a number of Swedish provinces, including Biatoropsis usnearum, Syzygospora bachmannii, S. physciacearum, Tremella caloplacae, T. cetrariicola, T. cladoniae, T. coppinsii, T. diploschistina, and T. hypogymniae.


Tremella rhizocarpicola sp. nov. and other interesting lichenicolous Tremellales and Filobasidiales in the Nordic countries Introduction
Fungal mycoparasites, including lichen-parasites, are common among the Tremellomycetes (Basidiomycota, Fungi).Lichen-inhabiting species belong to the genera Biatoropsis, Tremella (both Tremellales) and Syzygospora (Filobasidiales).There are currently 50 lichenicolous species described in the group (Diederich 1986, 1996, 2003, Sérusiaux et al. 2003, Diederich 2007, Zamora et al. 2011, Millanes et al. 2012), and an additional five are known but have not yet been formally named (Diederich 1996(Diederich , 2007)).The actual diversity and distribution of lichen-inhabiting species is still largely unknown, as comparatively few mycologists and lichenologists collect lichenicolous fungi.Some tremellalean species are relatively easy to spot in the field as they induce the formation of conspicuous galls on the hosts, whereas others grow only inside the host hymenium producing few or no external symptoms.In these cases, study of host herbarium material is extremely useful for diversity surveys, and also improves our knowledge on the geographical distribution of taxa that are otherwise much overlooked in the field.In the Nordic countries, 15 tremellalean lichenicolous species have been reported so far (Nordin et al. 2014).During fieldwork in Sweden and Norway, and herbarium surveys undertaken in BG, S, and UPS, during 2012-2014, we found material allowing one new species to be formally described and several species to be newly reported to the Nordic countries, Iceland, Norway or Sweden.

Methods
Macromorphological traits were observed using a Zeiss Stemi 2000-C dissecting microscope.Microscopic structures were studied using handmade sections stained with Phloxin (1% in water) after pre-treatment with KOH (5%), following the methods of Diederich (1996), and observed with a Zeiss Axioscope-2 microscope.Macro-and microscopic photographs were taken with a Nikon Coolpix 995 camera fitted to both microscopes.The apiculus is not included in basidiospore measurements.Sizes in parentheses represent minimum and maximum observed values.
Distribution, ecology and host.The new species is known from one locality in Denmark, two localities in Norway, and nine in Sweden, all growing inside the hymenium of Rhizocarpon lavatum on siliceous rocks, often along shorelines or near water.
Discussion.The species was tentatively described by Diederich (1996: 170) as Tremella sp. 3. The single specimen known at that time was very small, but the discovery of 12 additional collections from Denmark, Sweden and Norway (Fig. 1A) is now enough for a formal description.There is little to add to the description and illustrations given by Diederich (1996), however.The only novelties are the wider range of basidium width and length (Fig. 1G) and the presence, occasionally, of an anamorph consisting of catenulate conidia.A sequence of the ITS barcode region is not provided, since recently collected specimens were too reduced for DNA extraction, and old specimens could not be amplified by PCR.Diederich (1996) indicated that this species was microscopically very similar to Tremella protoparmeliae, but T. rhizocarpicola could be distinguished by the formation of dark brown swellings on the host apothecia and by small differences in the size of the basidia.The additional specimens studied here show that there is an anamorph formed by catenulate conidia in T. rhizocarpicola, and the basidia of this species can be comparatively shorter and wider than those of T. protoparmeliae.

New records to the Nordic countries
Tremella pertusariae Diederich Note.This species was previously recorded in Europe (Belgium, France, Germany, Great Britain, Ireland, Italy, and Spain), where it is very common in the western Pyrenees, and in America (Mexico and U.S.A) (Diederich 1996).Knutsson and Johansson (2011) reported it from Sweden, but with some hesitation since the material could not be identified microscopically.The five additional specimens reported here confirm the presence of the species in the Nordic countries.The fungus forms pale to dark brown or blackish galls, generally on the apothecia of Pertusaria hymenea (Fig. 1B), but also on the thallus of both P. hymenea and P. pertusa, and bears characteristic stalked basidia (Fig. 1H).

Tremella protoparmeliae Diederich & Coppins
Note.This species was previously only recorded in England (Diederich 1996).The fungus grows intrahymenially on Protoparmelia badia, without producing any external symptoms, which suggests that this species could in reality be common, but much overlooked as it is not visible macroscopically (Figs.1C and 1I).
The species was at first tentatively described as Tremella sp. 1 by Diederich (1996) and eventually formally described by Sérusiaux et al. (2003).It has been reported from Austria, Canada, France, Great Britain, Greece, Greenland, and Spain (Diederich 1996, 2007, Sérusiaux et al. 2003), growing inside the hymenia, or exceptionally on the thallus, of different Caloplaca species, viz. C. arenaria, C. arnoldii, C. aurantia, C. carphinea andC. saxicola (Diederich 1996, Sérusiaux et al. 2003), and on the thallus of Xanthoria sorediata (Diederich 2007).It was recently reported as new to the Nordic countries (Thell et al. 2014) from two Swedish collections, growing on new hosts: Caloplaca decipiens (on the thallus; Fig. 1D) and Xanthoria parietina (inside the hymenium; Fig. 1E).Here it is reported on a new host (Xanthoria elegans), in Sweden.All samples below are on X. elegans, growing inside the hymenium or on the thallus.All specimens bear two-celled basidia (Fig. 1J) and are very similar microscopically.Further investigations are needed, however, to check if all specimens growing on Teloschistaceae belong to a single species.

Records new to some provinces in Sweden
Biatoropsis usnearum Räsänen Note.New to Bohuslän.
This species has a wide distribution and has been recorded in all Nordic countries except Iceland (i.e., Denmark, Finland, Norway, and Sweden) (Diederich andChristiansen 1994, Nordin et al. 2014).
New specimen examined.SWEDEN.Bohuslän, Kville/Tanum pars., following Torsbo stream, low part of the cliff, mixed forest with Alnus, Betula, Corylus, Picea and Salix, on Usnea sp., 58°47.55'N, 11°8,4'E, 14 Apr 2013, A. Millanes 695 (S: F-255315).This material had been placed in S long ago, but as the specimens have apparently not been published or otherwise recorded elsewhere, we report them here.The species had been previously recorded in the Nordic countries, particularly in Sweden and Finland (Diederich 1996).
In the Nordic countries this species has been recorded in Finland, Norway and Sweden (Diederich 1996, Pippola andKotiranta 2008).
The species has previously been recorded in the Scandinavian Peninsula, i.e., Norway and Sweden (Holien andTønsberg 1994, Diederich 1996).