The UNITE database for molecular identification and taxonomic communication of fungi and other eukaryotes: sequences, taxa and classifications reconsidered

UNITE (https://unite.ut.ee) is a web-based database and sequence management environment for molecular identification of eukaryotes. It targets the nuclear ribosomal internal transcribed spacer (ITS) region and offers nearly 10 million such sequences for reference. These are clustered into ∼2.4M species hypotheses (SHs), each assigned a unique digital object identifier (DOI) to promote unambiguous referencing across studies. UNITE users have contributed over 600 000 third-party sequence annotations, which are shared with a range of databases and other community resources. Recent improvements facilitate the detection of cross-kingdom biological associations and the integration of undescribed groups of organisms into everyday biological pursuits. Serving as a digital twin for eukaryotic biodiversity and communities worldwide, the latest release of UNITE offers improved avenues for biodiversity discovery, precise taxonomic communication and integration of biological knowledge across platforms.

A phylogenetic assessment of a fungicolous lineage in Coniocybomycetes: Chaenotricha, a new genus of Trichaptum-inhabiting species

The globally distributed genus Trichaptum is one of the most species-rich among polypores in terms of hosting other fungi. Among Trichaptum-associates, there is a group of mazaediate lichenized fungi (Coniocybomycetes, Ascomycota) that previously had an uncertain phylogenetic position. DNA sequences - mitochondrial small subunit (mtSSU), nuclear large subunit rDNA (nuLSU), and internal transcribed spacer (ITS) - were obtained from 29 specimens collected from Europe and North America. Maximum likelihood and Bayesian inference analyses of these three gene loci were used to infer phylogenetic position and relationships among lineages. Statistical tests were used to find which phenotypical characteristics distinguish species. The molecular sequence data provide evidence that the fungicolous specimens form a distinct lineage within Coniocybomycetes sister to the combined clade of Chaenotheca s. lat. and Sclerophora. Considering its phylogenetic placement and strict specialization, we describe a new genus - Chaenotricha. This fungicolous lineage contains three species based on molecular characteristics. Morphological characters mostly overlap except for spore size and stalk length of apothecia. We provide a new combination, Chaenotricha obscura, for the only previously described species for which we designate an epitype, and introduce a new species - Chaenotricha cilians. The third lineage remains undescribed because of a small sample size, which did not allow us to clearly delineate species boundaries. Citation: Suija A, McMullin RT, Lõhmus P (2023). A phylogenetic assessment of a fungicolous lineage in Coniocybomycetes: Chaenotricha, a new genus of Trichaptum-inhabiting species. Fungal Systematics and Evolution 12: 255-269. doi: 10.3114/fuse.2023.12.13.

Refined families of Dothideomycetes: orders and families incertae sedis in Dothideomycetes

Numerous new taxa and classifications of Dothideomycetes have been published following the last monograph of families of Dothideomycetes in 2013. A recent publication by Honsanan et al. in 2020 expanded information of families in Dothideomycetidae and Pleosporomycetidae with modern classifications. In this paper, we provide a refined updated document on orders and families incertae sedis of Dothideomycetes. Each family is provided with an updated description, notes, including figures to represent the morphology, a list of accepted genera, and economic and ecological significances. We also provide phylogenetic trees for each order. In this study, 31 orders which consist 50 families are assigned as orders incertae sedis in Dothideomycetes, and 41 families are treated as families incertae sedis due to lack of molecular or morphological evidence. The new order, Catinellales, and four new families, Catinellaceae, Morenoinaceae Neobuelliellaceae and Thyrinulaceae are introduced. Seven genera (Neobuelliella, Pseudomicrothyrium, Flagellostrigula, Swinscowia, Macroconstrictolumina, Pseudobogoriella, and Schummia) are introduced. Seven new species (Acrospermum urticae, Bogoriella complexoluminata, Dothiorella ostryae, Dyfrolomyces distoseptatus, Macroconstrictolumina megalateralis, Patellaria microspora, and Pseudomicrothyrium thailandicum) are introduced base on morphology and phylogeny, together with two new records/reports and five new collections from different families. Ninety new combinations are also provided in this paper.

The Taxon Hypothesis Paradigm-On the Unambiguous Detection and Communication of Taxa

Here, we describe the taxon hypothesis (TH) paradigm, which covers the construction, identification, and communication of taxa as datasets. Defining taxa as datasets of individuals and their traits will make taxon identification and most importantly communication of taxa precise and reproducible. This will allow datasets with standardized and atomized traits to be used digitally in identification pipelines and communicated through persistent identifiers. Such datasets are particularly useful in the context of formally undescribed or even physically undiscovered species if data such as sequences from samples of environmental DNA (eDNA) are available. Implementing the TH paradigm will to some extent remove the impediment to hastily discover and formally describe all extant species in that the TH paradigm allows discovery and communication of new species and other taxa also in the absence of formal descriptions. The TH datasets can be connected to a taxonomic backbone providing access to the vast information associated with the tree of life. In parallel to the description of the TH paradigm, we demonstrate how it is implemented in the UNITE digital taxon communication system. UNITE TH datasets include rich data on individuals and their rDNA ITS sequences. These datasets are equipped with digital object identifiers (DOI) that serve to fix their identity in our communication. All datasets are also connected to a GBIF taxonomic backbone. Researchers processing their eDNA samples using UNITE datasets will, thus, be able to publish their findings as taxon occurrences in the GBIF data portal. UNITE species hypothesis (species level THs) datasets are increasingly utilized in taxon identification pipelines and even formally undescribed species can be identified and communicated by using UNITE. The TH paradigm seeks to achieve unambiguous, unique, and traceable communication of taxa and their properties at any level of the tree of life. It offers a rapid way to discover and communicate undescribed species in identification pipelines and data portals before they are lost to the sixth mass extinction.

Phylogenetic placement and lectotypification of Pseudotryblidium neesii (Helotiales, Leotiomycetes)

A phylogenetic analysis of combined rDNA LSU and ITS sequence data was carried out to determine the phylogenetic placement of specimens identified as Pseudotryblidium neesii. The species forms a distinct clade within Dermateaceae (Helotiales, Leotiomycetes) with Rhizodermea veluwiensis and two Dermea species. The geographical distribution of this species, previously known only from Europe on Abies alba, is extended to north-western North America where it grows exclusively on A. grandis. The name P. neesii is lectotypified in order to disentangle the complicated nomenclature of the species. A new, detailed description of P. neesii with illustrations is provided after comparison of sequenced specimens with the type material. Furthermore, the new combination Pseudographis rufonigra (basionym Peziza rufonigra) is made for a fungus previously known as Pseudographis pinicola.

Considerations and consequences of allowing DNA sequence data as types of fungal taxa

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.

Lichenicolous species of Hainesia belong to Phacidiales (Leotiomycetes) and are included in an extended concept of Epithamnolia

The lichenicolous taxa currently included in the genus Hainesia were studied based on the nuclear rDNA (18S, 28S, and internal transcribed spacer [ITS]) genes. The authors found that lichenicolous taxa form a distinct lineage sister to Epiglia gloeocapsae (Phacidiales, Leotiomycetes), only distantly related to the type species of Hainesia (Chaetomellaceae, Helotiales). Owing to morphological similarities, the authors include the lichenicolous species into the previously monotypic genus Epithamnolia. A new species, Epithamnolia rangiferinae, is described, several names are reduced into synonymy, and a key to the species of Epithamnolia is provided. The incorporation of public environmental ITS sequences showed that the closest relatives of these lichenicolous taxa are various endophytic, endolichenic, and soil-inhabiting fungi.

Fungal biogeography. Global diversity and geography of soil fungi

Fungi play major roles in ecosystem processes, but the determinants of fungal diversity and biogeographic patterns remain poorly understood. Using DNA metabarcoding data from hundreds of globally distributed soil samples, we demonstrate that fungal richness is decoupled from plant diversity. The plant-to-fungus richness ratio declines exponentially toward the poles. Climatic factors, followed by edaphic and spatial variables, constitute the best predictors of fungal richness and community composition at the global scale. Fungi show similar latitudinal diversity gradients to other organisms, with several notable exceptions. These findings advance our understanding of global fungal diversity patterns and permit integration of fungi into a general macroecological framework.

Towards a unified paradigm for sequence-based identification of fungi

The nuclear ribosomal internal transcribed spacer (ITS) region is the formal fungal barcode and in most cases the marker of choice for the exploration of fungal diversity in environmental samples. Two problems are particularly acute in the pursuit of satisfactory taxonomic assignment of newly generated ITS sequences: (i) the lack of an inclusive, reliable public reference data set and (ii) the lack of means to refer to fungal species, for which no Latin name is available in a standardized stable way. Here, we report on progress in these regards through further development of the UNITE database (http://unite.ut.ee) for molecular identification of fungi. All fungal species represented by at least two ITS sequences in the international nucleotide sequence databases are now given a unique, stable name of the accession number type (e.g. Hymenoscyphus pseudoalbidus|GU586904|SH133781.05FU), and their taxonomic and ecological annotations were corrected as far as possible through a distributed, third-party annotation effort. We introduce the term 'species hypothesis' (SH) for the taxa discovered in clustering on different similarity thresholds (97-99%). An automatically or manually designated sequence is chosen to represent each such SH. These reference sequences are released (http://unite.ut.ee/repository.php) for use by the scientific community in, for example, local sequence similarity searches and in the QIIME pipeline. The system and the data will be updated automatically as the number of public fungal ITS sequences grows. We invite everybody in the position to improve the annotation or metadata associated with their particular fungal lineages of expertise to do so through the new Web-based sequence management system in UNITE.