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.

The Helotiales are an ecologically and morphologically highly diverse group of ascomycetes that also includes lichen-inhabiting (lichenicolous) species. We generated sequence data of three rDNA regions (nuSSU, nuLSU, 5.8S of ITS) from 28 lichenicolous specimens representing nine genera in order to determine their phylogenetic placement. Based on the most complete dataset of helotialean fungi to date, the analyses were performed using Maximum Likelihood (ML) and Bayesian approaches. Our results suggest that 1) the lichen-inhabiting life-style in Helotiales was subjected to gains or losses at least three times; 2) Thamnogalla, previously tentatively included in Ostropales, is shown to belong to Helotiales; 3) ascomata found intermixed with pycnidia of the asexual Diplolaeviopsis ranula and possessing the same pigments are tentatively considered as the sexual morph of this taxon, and are shown to belong to Helotiales; 4) the lichenicolous species of cf. Diplolaeviopsis, Llimoniella, Rhymbocarpus, Skyttea, Thamnogalla and Unguiculariopsis form a well-supported clade together with non-lichenicolous encoelioid fungi from the genera Ionomidotis, Cordierites and Encoelia; 5) Geltingia associata forms a highly supported clade with the fungicolous asexual fungus Eleutheromyces subulatus, whereas Pezizella epithallina clusters with an aquatic asexual fungus Tetracladium sp.; 6) Phaeopyxis punctum belongs to Ostropomycetidae (Lecanoromycetes), but its deep relationships to other groups remain unresolved based on rDNA sequences.

During lichenological explorations of tropical montane forests in Kenya, a remarkable new lichenicolous fungus was repeatedly found growing on thalli of the epiphytic tripartite cyanolichen Crocodia cf. clathrata. Molecular phylogenetic analyses placed the fungus within Gomphillaceae (Ostropales, Lecanoromycetes), a family mainly of lichen-symbiotic species in the tropics. The anatomical features (unitunicate, non-amyloid asci and simple, septate paraphyses) as well as the hemiangiocarpic ascoma development confirm its taxonomic affinity. DNA sequence data showed the closest relationship was with Gyalidea fritzei, followed by Corticifraga peltigerae. A monotypic genus, Taitaia, is introduced to incorporate a single species, T. aurea. The new fungus is characterized by aggregated ascomata with yellow margins and salmon red discs developing from a single base.

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.