Complex life-cycles are common among fungi. Dimorphism in basidiomycetes involves alternation between a unicellular yeast phase and a filamentous phase, frequently forming basidiomata. Here we have studied the dimorphic life cycle of the lichen-inhabiting basidiomycetes in the Tremella caloplacae species complex, with particular focus on the newly distinguished Tremella parietinae. Using FISH-CLSM, PCR and Sanger sequencing, we have investigated the presence and distribution of the different life-cycle phases of T. parietinae within the lichen Xanthoria parietina, and also conducted an exploratory investigation into the presence of a Tremella yeast phase in other lichens of the Teloschistaceae. We could show that the filamentous phase of T. parietinae is restricted to the hymenium of X. parietina, whereas the yeast phase also grows elsewhere in the thallus. Tremella caloplacae s. str. is detected by PCR in Calogaya, Flavoplaca and Gyalolechia lichens, whereas its basidiomata are restricted to Variospora lichens. These findings suggests different lichen-specificity of T. caloplacae in the different phases of its life-cycle.

Many fungi have a dimorphic life cycle, alternating between unicellular yeast and multicellular filamentous phases. Although dimorphism is assumed for many lichen-associated basidiomycetes, the existence of a yeast stage has rarely been confirmed. Using taxon-specific PCR and FISH-CLSM, we studied Tremella hypogymniae and T. tubulosae Tremellomycetes), two presumably dimorphic species previously known only from their filamentous phase in galls on the lichens Hypogymnia physodes and H. tubulosa, respectively. We investigated their presence and frequency, lichen ranges and within-thallus distribution of life-cycle stages. We also explored the co-occurrence of both species with Cystobasidiomycetes-one of the most widespread lichen-associated yeast lineages-in the same lichen thalli. The filamentous phase of Tremella hypogymniae and T. tubulosae was confined to a single lichen species each, whereas the yeast phase occurred in several closely related lichens. Both phases co-occurred with various Cystobasidiomycete lineages. Filamentous structures were restricted to galls, whereas gall-free thalli contained Tremella yeasts in the cortex, soredia and medulla, and pseudohyphae in the cortex. The presence of yeasts in soredia suggests co-dispersal with other lichen symbionts. These findings reveal narrow specificity in the filamentous phase but broader associations in the yeast phase, pointing to complex interactions within the lichen symbiosis.

Lichens represent one of the most successful examples of symbiosis. They are constituted by the association between a dominant fungus (i.e., the mycobiont), one or more photosynthetic partners (algae or cyanobacteria), and harbor an array of associated microorganisms, including bacteria and fungi. The associated fungal communities in lichens, known as the “lichen mycobiome”, are composed of both ascomycetes and basidiomycetes, including filamentous and yeast taxa. Recently, basidiomycete yeasts have received considerable attention as a much-overlooked source of diversity within the lichen mycobiome, with hypothesized roles in lichen symbiosis. This study surveyed the diversity of cultivable basidiomycete yeasts associated with Peltigera lichens across southern Chile. A phylogenetic study based on sequences of 179 yeast isolates allowed the identification of 29 taxa from 13 genera in the classes Agaricostilbomycetes, Cystobasidiomycetes, Microbotryomycetes, and Tremellomycetes, with the latter being the most represented. This research revealed several yeast species, including members of the genera Boekhoutia and Goffeauzyma, in lichens for the first time, thereby expanding our understanding of lichen-associated fungal diversity. In addition, four new cultivable species isolated from Peltigera are formally described. These are Boekhoutia peltigerae sp. nov., Cystobasidium chilense sp. nov., Genolevuria patagonica sp. nov. and Pseudotremella navarinensis sp. nov. These results highlight the role of lichens as reservoirs of uncharacterized basidiomycete yeasts.

AbstractTremella caloplacae (Zahlbr.) Diederich is a species complex including at least nine different species. Here, we formally describe the new species Tremella elegantis, T. nimisiana, T. parietinae, T. pusillae and T. sorediatae. Tremella elegantis induces galls in the hymenium of Rusavskia elegans and forms 2-celled basidia, where cells rarely elongate and sometimes give the appearance of two immature, independent basidia. Tremella nimisiana has small basidiomata (less than 1 mm diam.), narrowly ellipsoid to pyriform 2-celled, occasionally clavate to subcylindrical 3-celled basidia, and grows in the hymenium of Xanthocarpia species. Tremella parietinae is characterized by the exclusive growth in the hymenium of Xanthoria parietina, the broadly fusiform to ellipsoid probasidia, and the subspherical, pyriform or ellipsoid 2(–3)-celled basidia. Tremella pusillae has ellipsoidal probasidia, 2(–3)-celled pyriform or ellipsoidal basidia that sometimes are constricted at the septum, and grows only on Calogaya pusilla. Tremella sorediatae is characterized by inducing galls on the thallus of Rusavskia sorediata and by pyriform to ellipsoid basidia that sometimes are constricted at the septum. Three species are not formally described and are left unnamed as Tremella sp. 13 on Calogaya biatorina, Tremella sp. 14 on Calogaya decipiens and Tremella sp. 15 on Polycauliona sp. Tremella caloplacae in the strict sense is re-circumscribed as a species confined to Variospora species.

Lichenicolous fungi are a heterogeneous group of organisms that grow exclusively on lichens, forming obligate associations with them. It has often been assumed that cospeciation has occurred between lichens and lichenicolous fungi, but this has been seldom analysed from a macroevolutionary perspective. Many lichenicolous species are rare or are rarely observed, which results in frequent and large gaps in the knowledge of the diversity of many groups. This, in turn, hampers evolutionary studies that necessarily are based on a reasonable knowledge of this diversity. Tremella caloplacae is a heterobasidiomycete growing on various hosts from the lichen-forming family Teloschistaceae, and evidence suggests that it may represent a species complex. We combine an exhaustive sampling with molecular and ecological data to study species delimitation, cophylogenetic events and temporal concordance of this association. Tremella caloplacae is here shown to include at least six distinct host-specific lineages (=putative species). Host switch is the dominant and most plausible event influencing diversification and explaining the coupled evolutionary history in this system, although cospeciation cannot be discarded. Speciation in T. caloplacae would therefore have occurred coinciding with the rapid diversification - by an adaptive radiation starting in the late Cretaceous - of their hosts. New species in T. caloplacae would have developed as a result of specialization on diversifying lichen hosts that suddenly offered abundant new ecological niches to explore or adapt to.

While most lichenicolous fungi belong to the Ascomycota, c. 5% of them are members of the Basidiomycota. Among these, the poorly known genus Crittendenia in the Pucciniomycotina has recently been described for lichenicolous fungi with minuscule needle-like synnematous basidiomata. Although only two species were hitherto known, the wide observed host-spectrum suggested a larger number of mainly host-specific species. A classical revision using morphological characters alone proved to be virtually impossible, because of the large variability of the material from each host genus, and the scant morphological differences between hypothetically distinct species from different hosts. We studied over sixty specimens and made a large number of measurements of the available morphological characters. We additionally generated 18 ITS and 21 nuLSU rDNA sequences and conducted maximum likelihood and Bayesian analyses. We also performed one species delimitation analysis (bPTP-ML). By combining sometimes subtle morphological differences, host choice and phylogenetic results, we were able to accept eighteen morphologically and/or genetically distinct species, all confined to a single host genus or to several closely related host genera. Two further putative species are left unnamed, as richer material is needed and molecular data are missing. Sixteen new species are described: Crittendenia absistentis (on Bacidia absistens), C. bacidinae (on Bacidina apiahica), C. bryostigmatis (on Bryostigma muscigenum), C. byssolomatis (on Byssoloma maderense), C. crassitunicata (on Melanohalea ushuaiensis), C. heterodermiae (on Heterodermia comosa), C. hypotrachynae (on Hypotrachyna), C. kakouettae (on 'Byssoloma' kakouettae), C. lecanorae (on Lecanora), C. lecidellae (on Lecidella elaeochroma), C. lopadii (on Lopadium disciforme), C. parvispora (on Bacidia), C. physciiphila (on Phaeophyscia, Physcia and Physciella), C. physconiae (on Physconia distorta), C. stickle (on Sticta fuliginosa) and C. teloschistis (on Teloschistes). Further, a ML analysis of the Agaricostilbomycetes using ITS and nuLSU sequences suggested that Crittendenia cannot be included in any known family, and the new family Crittendeniaceae is therefore described for the genus.

Fungi are eukaryotes that play essential roles in ecosystems. Among fungi, Basidiomycota is one of the major phyla with more than 40,000 described species. We review species diversity of Basidiomycota from five groups with different lifestyles or habitats: saprobic in grass/forest litter, wood-decaying, yeast-like, ectomycorrhizal, and plant parasitic. Case studies of Agaricus, Cantharellus, Ganoderma, Gyroporus, Russula, Tricholoma, and groups of lichenicolous yeast-like fungi, rust fungi, and smut fungi are used to determine trends in discovery of biodiversity. In each case study, the number of new species published during 2009–2020 is analysed to determine the rate of discovery. Publication rates differ between taxa and reflect different states of progress for species discovery in different genera. The results showed that lichenicolous yeast-like taxa had the highest publication rate for new species in the past two decades, and it is likely this trend will continue in the next decade. The species discovery rate of plant parasitic basidiomycetes was low in the past ten years, and remained constant in the past 50 years. We also found that the establishment of comprehensive and robust taxonomic systems based on a joint global initiative by mycologists could promote and standardize the recognition of taxa. We estimated that more than 54,000 species of Basidiomycota will be discovered by 2030, and estimate a total of 1.4–4.2 million species of Basidiomycota globally. These numbers illustrate a huge gap between the described and yet unknown diversity in Basidiomycota.

Lichens are well-known examples of complex symbiotic associations between organisms from different Kingdoms. Microfungi in particular, establish diverse associations with the hosting lichen thallus, as species-specific parasites or transient co-inhabitants. The whole community of lichen-associated fungi constitute the ???lichen mycobiome??? comprising both ascomycetes and basidiomycetes, including filamentous and yeast taxa. Metabarcoding results and microscopy analyses show that in some thalli, basidiomycetes are frequent lichen-associated fungi but still only a few species could be axenically isolated and morphologically characterized. Within a broad project aiming at characterizing the mycobiome diversity by culture-dependent and independent approaches in two lichen species selected as reference models - Rhizoplaca melanophthalma and Tephromela atra, we succeed in isolating and culturing 76 new strains of basidiomycetous yeasts. The lichen thalli were collected in different mountain regions worldwide and at relatively high elevation. The yeast strains were isolated on different growth media and were studied for their morphological and genetic diversity. Nuclear internal transcribed spacer (ITS) and ribosomal large subunit (LSU) sequence analyses identified them to belong to ten families within the orders Agaricostilbomycetes, Cystobasidiomycetes, Microbotryomycetes, Tremellomycetes and Ustilaginomycetes. The yeasts here detected showed patterns of host-preference in a few cases and they are potentially related to the ecological conditions. ?? 2022 British Mycological Society. Published by Elsevier Ltd. All rights reserved.

Abstract The lichenicolous ‘heterobasidiomycetes’ belong in the Tremellomycetes (Agaricomycotina) and in the Pucciniomycotina. In this paper, we provide an introduction and review of these lichenicolous taxa, focusing on recent studies and novelties of their classification, phylogeny and evolution. Lichen-inhabiting fungi in the Pucciniomycotina are represented by only a small number of species included in the genera Chionosphaera, Cyphobasidium and Lichenozyma. The phylogenetic position of the lichenicolous representatives of Chionosphaera has, however, never been investigated by molecular methods. Phylogenetic analyses using the nuclear SSU, ITS, and LSU ribosomal DNA markers reveal that the lichenicolous members of Chionosphaera form a monophyletic group in the Pucciniomycotina, distinct from Chionosphaera and outside the Chionosphaeraceae. The new genus Crittendenia is described to accommodate these lichen-inhabiting species. Crittendenia is characterized by minute synnemata-like basidiomata, the presence of clamp connections and aseptate tubular basidia from which 4–7 spores discharge passively, often in groups. Crittendenia, Cyphobasidium and Lichenozyma are the only lichenicolous lineages known so far in the Pucciniomycotina, whereas Chionosphaera does not include any lichenicolous taxa.

The lichenicolous fungi growing on Graphidales hosts in Florida are revised, mainly based on collections by the second author (R. C.). Twenty-one species are recognized. The new genus and species Lawreya glyphidiphila is described for a common asexual fungus growing on Glyphis scyphulifera and more rarely Trypethelium eluteriae , characterized by black stromatic conidiomata in which subspherical conidiogenous loculi develop, producing aseptate, subglobose, brown conidia. Nine additional new species are described: Amerosporiopsis phaeographidis (on Phaeographis brasiliensis ), Arthonia acanthotheciicola (on Acanthothecis floridensis ), A. subgraphidicola (on Graphis assimilis ), Hemigrapha graphidicola (on G. assimilis ), Skyttea graphidicola (on Graphis spp.), Strigula graphidicola (on G. assimilis ), S. perparvula (on Graphidales ), Talpapellis graphidis (on Graphis caesiella ) and Tremella wedinii (on Glyphis scyphulifera ). Phylogenetic placements of Lawreya glyphidiphila , Skyttea graphidicola and Tremella wedinii are presented. Identification keys are given for the species of Cornutispora and Talpapellis , and for the 66 species known to grow on Graphidales hosts worldwide.

Nomenclatural type definitions are one of the most important concepts in biological nomenclature. Being physical objects that can be re-studied by other researchers, types permanently link taxonomy (an artificial agreement to classify biological diversity) with nomenclature (an artificial agreement to name biological diversity). Two proposals to amend the International Code of Nomenclature for algae, fungi, and plants (ICN), allowing DNA sequences alone (of any region and extent) to serve as types of taxon names for voucherless fungi (mainly putative taxa from environmental DNA sequences), have been submitted to be voted on at the 11th International Mycological Congress (Puerto Rico, July 2018). We consider various genetic processes affecting the distribution of alleles among taxa and find that alleles may not consistently and uniquely represent the species within which they are contained. Should the proposals be accepted, the meaning of nomenclatural types would change in a fundamental way from physical objects as sources of data to the data themselves. Such changes are conducive to irreproducible science, the potential typification on artefactual data, and massive creation of names with low information content, ultimately causing nomenclatural instability and unnecessary work for future researchers that would stall future explorations of fungal diversity. We conclude that the acceptance of DNA sequences alone as types of names of taxa, under the terms used in the current proposals, is unnecessary and would not solve the problem of naming putative taxa known only from DNA sequences in a scientifically defensible way. As an alternative, we highlight the use of formulas for naming putative taxa (candidate taxa) that do not require any modification of the ICN.

Sugarcane plants, subjected to environmental stress, mechanical injuries, or infection by pathogens, produce glycoproteins containing heterofructans, composed of a fairly extensive domain of β-1,2-fructofuranoside chains in which galactitol units intercalated. They could act as signaling molecules for cell recognition, able to discriminate between beneficial endophytes and bacterial or fungal pathogens. Infection mechanisms and disease progress are very different for different pathogens. Xanthomonas albilineans produces a gum, a xanthanlike polymer, which obliterates the xylem elements producing desiccation and leaf yellowing, and this disease has been termed “leaf scald.” Sporisorium scitamineum, on the other hand, uses stomata to penetrate the host tissues or secretes hydrolytic enzymes of cell wall polymers, which enable mycelial entry through any point on the surface of the plant. Pathogen spores also secrete quorum signals that increase the number of cells in the inoculum. However, some of the glycoproteins produced by infected cane act as false quorum signals. Then the probability of inhibiting germination increases by increasing the aggregation of the teliospores caused by noxious false signals. Alternatively, infection of sugarcane plants by smut teliospores elicits lignification by activating monolignol production. Lignin deposits increase in the cell walls of the infected plant and impede the entry of the pathogen. Teliospores must displace on the wet surface of the plant, either to find a natural way of entry or to be grouped by the effect of quorum sensing. The displacement occurs by successive contractions and relaxations of the actomyosin complex that composes the cytoskeleton.

Tremella mayrhoferi, inducing galls on the hymenium of Lecanora allophana, is described. The description is based on molecular, morphological and ecological data of 27 specimens from Finland, Norway, Spain, Sweden, and USA. The new species is easily distinguished from other lichenicolous Tremella species by its characteristic basidia with cells that elongate before the formation of epibasidia, combined with the macromorphology and host selection. Molecular phylogeny suggests that it forms a group with other species growing on Lecanora s. lat. and Lecidea s. lat., which is related to the Tremella species growing on Parmeliaceae, but not to Tremella s. str.

Tremella anaptychiae, a lichenicolous fungus growing on Anaptychia ciliaris, is described as new. Both morphological and molecular data (DNA sequences from the ITS and 28S regions) are used to characterize and distinguish it from other Tremella s. l. species. Tremella anaptychiae is closely related to T. parmeliarum but comparatively distantly related to other previously recognized lichenicolous species groups.

The lichen-forming genus Parmelia Acharius occurs worldwide but its centre of distribution is in the northern hemisphere and it is widespread in boreal-temperate Eurasia and North America. Recent molecular work on Parmelia has identified phylogenetic relationships within two major groups of the genus: P. saxatilis s. lat. and P. sulcata s. lat. However, little is known about the diversification and historical biogeography of these groups. Here we have used a dataset of two genetic markers and 64 samples to estimate phylogenetic relationships within Parmelia. The dated phylogeny provides evidence for major diversification during the Neogene and Pleistocene. These diversification events are probably correlated with climatic changes during these periods. Evidence of gene flow within species between populations from North America and Europe has been found in three species: P. sulcata Taylor, P. saxatilis (L.) Acharius and P. barrenoae Divakar, M.C. Molina & A. Crespo. Cryptic species recently segregated on the basis of molecular differences (P. encryptata A. Crespo, Divakar & M.C. Molina vs. P. sulcata and P. saxatilis vs. P. mayi Divakar, A. Crespo & M.C. Molina) do not share a common ancestor. Moreover, the P. saxatilis complex is remarkably diverse. Two morphotypes of P. saxatilis s. lat. were shown to represent independent monophyletic lineages. Consequently, two species (P. sulymae Goward, Divakar, & M.C. Molina & A. Crespo and P. imbricaria Goward, Divakar, M.C. Molina & A. Crespo) are newly described here.

The new combination Phaeotremella foliacea (Pers.) Wedin, J. C. Zamora & Millanes is coined and taken up as the current name for one of the most common species of the recently resurrected genus Phaeotremella Rea.

Three new species of Biatoropsis are formally described based on our previous molecular studies, and on additional molecular, morphological, and ecological data. Biatoropsis protousneae sp. nov. is confined to Protousnea dusenii. Biatoropsis minuta sp. nov. is characterized by the small and brown to black basidiomatal galls, and by growing on Usnea barbata and U. lapponica. Biatoropsis hafellneri sp. nov. is distinguished by 2-celled basidia with cells that elongate laterally at maturity, and by growing on species of the Usnea fragilescens aggregate. A fourth Biatoropsis species is left unnamed, and two other lineages are not described, all waiting for the study of additional material.

The place of publication and typification of the generic name Naematelia is discussed, and N. encephala is confirmed as the correct name of the type of the genus name. That name was a replacement name for the earlier N. encephaliformis, which is lectotypified by a Willdenow plate; as selection of an epitype cannot be justified at present, a sequenced specimen from Sweden is selected as a reference specimen to represent the molecular application of the name in our sense. As the name N. encephala is a sanctioned name, it must be retained over N. encephaliformis. The species is fungicolous, widespread, growing mainly on Stereum sanguinolentum on conifers, but also reported on deciduous trees.

Interesting lichenized and lichenicolous fungi found during the Nordic Lichen Society excursion in Nord-Trondelag, Norway 2015