How, not if, is the question mycologists should be asking about DNA-based typification.

Fungal metabarcoding of substrates such as soil, wood, and water is uncovering an unprecedented number of fungal species that do not seem to produce tangible morphological structures and that defy our best attempts at cultivation, thus falling outside the scope of the International Code of Nomenclature for algae, fungi, and plants. The present study uses the new, ninth release of the species hypotheses of the UNITE database to show that species discovery through environmental sequencing vastly outpaces traditional, Sanger sequencing-based efforts in a strongly increasing trend over the last five years. Our findings challenge the present stance of some in the mycological community - that the current situation is satisfactory and that no change is needed to "the code" - and suggest that we should be discussing not whether to allow DNA-based descriptions (typifications) of species and by extension higher ranks of fungi, but what the precise requirements for such DNA-based typifications should be. We submit a tentative list of such criteria for further discussion. The present authors hope for a revitalized and deepened discussion on DNA-based typification, because to us it seems harmful and counter-productive to intentionally deny the overwhelming majority of extant fungi a formal standing under the International Code of Nomenclature for algae, fungi, and plants.

Reassessment of the generic limits for Hydnellum and Sarcodon (Thelephorales, Basidiomycota).

DNA sequences from the nuclear LSU and ITS regions were used for phylogenetic analyses of Thelephorales with a focus on the stipitate hydnoid genera Hydnellum and Sarcodon. Analyses showed that Hydnellum and Sarcodon are distinct genera but that the current division, based on basidioma texture, makes Sarcodon paraphyletic with respect to Hydnellum. In order to make genera monophyletic several species are moved from Sarcodon to Hydnellum and the following new combinations are made: Hydnellumamygdaliolens, H.fennicum, H.fuligineoviolaceum, H.fuscoindicum, H.glaucopus, H.joeides, H.lepidum, H.lundellii, H.martioflavum, H.scabrosum, H.underwoodii, and H.versipelle. Basidiospore size seems to separate the genera in most cases. Hydnellum species have basidiospore lengths in the range 4.45-6.95 µm while the corresponding range for Sarcodon is 7.4-9 µm. S.quercinofibulatus deviates from this pattern with an average spore length around 6 µm. Neotropical Sarcodon species represent a separate evolutionary lineage.

Solving the taxonomic identity of Pseudotomentellatristis s.l. (Thelephorales, Basidiomycota) - a multi-gene phylogeny and taxonomic review, integrating ecological and geographical data.

P.tristis is an ectomycorrhizal, corticioid fungus whose name is frequently assigned to collections of basidiomata as well as root tip and soil samples from a wide range of habitats and hosts across the northern hemisphere. Despite this, its identity is unclear; eight heterotypic taxa have in major reviews of the species been considered synonymous with or morphologically similar to P.tristis, but no sequence data from type specimens have been available. With the aim to clarify the taxonomy, systematics, morphology, ecology and geographical distribution of P.tristis and its morphologically similar species, we studied their type specimens as well as 147 basidiomata collections of mostly North European material. We used gene trees generated in BEAST 2 and PhyML and species trees estimated in STACEY and ASTRAL to delimit species based on the ITS, LSU, Tef1α and mtSSU regions. We enriched our sampling with environmental ITS sequences from the UNITE database. We found the P.tristis group to contain 13 molecularly and morphologically distinct species. Three of these, P.tristis, P.umbrina and P.atrofusca, are already known to science, while ten species are here described as new: P.sciastra sp. nov., P.tristoides sp. nov., P.umbrinascens sp. nov., P.pinophila sp. nov., P.alnophila sp. nov., P.alobata sp. nov., P.pluriloba sp. nov., P.abundiloba sp. nov., P.rotundispora sp. nov. and P.media sp. nov. We discovered P.rhizopunctata and P.atrofusca to form a sister clade to all other species in P.tristis s.l. These two species, unlike all other species in the P.tristis complex, are dimitic. In this study, we designate epitypes for P.tristis, P.umbrina and Hypochnopsisfuscata and lectotypes for Auriculariaphylacteris and Thelephorabiennis. We show that the holotype of Hypochnussitnensis and the lectotype of Hypochnopsisfuscata are conspecific with P.tristis, but in the absence of molecular information we regard Pseudotomentellalongisterigmata and Hypochnusrhacodium as doubtful taxa due to their aberrant morphology. We confirm A.phylacteris, Tomentellabiennis and Septobasidiumarachnoideum as excluded taxa, since their morphology clearly show that they belong to other genera. A key to the species of the P.tristis group is provided. We found P.umbrina to be a common species with a wide, Holarctic distribution, forming ectomycorrhiza with a large number of host species in habitats ranging from tropical forests to the Arctic tundra. The other species in the P.tristis group were found to be less common and have narrower ecological niches.

Introducing ribosomal tandem repeat barcoding for fungi.

Sequence comparison and analysis of the various ribosomal genetic markers are the dominant molecular methods for identification and description of fungi. However, new environmental fungal lineages known only from DNA data reveal significant gaps in our sampling of the fungal kingdom in terms of both taxonomy and marker coverage in the reference sequence databases. To facilitate the integration of reference data from all of the ribosomal markers, we present three sets of general primers that allow for amplification of the complete ribosomal operon from the ribosomal tandem repeats. The primers cover all ribosomal markers: ETS, SSU, ITS1, 5.8S, ITS2, LSU and IGS. We coupled these primers successfully with third-generation sequencing (PacBio and Nanopore sequencing) to showcase our approach on authentic fungal herbarium specimens (Basidiomycota), aquatic chytrids (Chytridiomycota) and a poorly understood lineage of early diverging fungi (Nephridiophagidae). In particular, we were able to generate high-quality reference data with Nanopore sequencing in a high-throughput manner, showing that the generation of reference data can be achieved on a regular desktop computer without the involvement of any large-scale sequencing facility. The quality of the Nanopore generated sequences was 99.85%, which is comparable with the 99.78% accuracy described for Sanger sequencing. With this work, we hope to stimulate the generation of a new comprehensive standard of ribosomal reference data with the ultimate aim to close the huge gaps in our reference datasets.

Taxonomic annotation of public fungal ITS sequences from the built environment - a report from an April 10-11, 2017 workshop (Aberdeen, UK).

Recent DNA-based studies have shown that the built environment is surprisingly rich in fungi. These indoor fungi - whether transient visitors or more persistent residents - may hold clues to the rising levels of human allergies and other medical and building-related health problems observed globally. The taxonomic identity of these fungi is crucial in such pursuits. Molecular identification of the built mycobiome is no trivial undertaking, however, given the large number of unidentified, misidentified, and technically compromised fungal sequences in public sequence databases. In addition, the sequence metadata required to make informed taxonomic decisions - such as country and host/substrate of collection - are often lacking even from reference and ex-type sequences. Here we report on a taxonomic annotation workshop (April 10-11, 2017) organized at the James Hutton Institute/University of Aberdeen (UK) to facilitate reproducible studies of the built mycobiome. The 32 participants went through public fungal ITS barcode sequences related to the built mycobiome for taxonomic and nomenclatural correctness, technical quality, and metadata availability. A total of 19,508 changes - including 4,783 name changes, 14,121 metadata annotations, and the removal of 99 technically compromised sequences - were implemented in the UNITE database for molecular identification of fungi (https://unite.ut.ee/) and shared with a range of other databases and downstream resources. Among the genera that saw the largest number of changes were Penicillium, Talaromyces, Cladosporium, Acremonium, and Alternaria, all of them of significant importance in both culture-based and culture-independent surveys of the built environment.