Two independent genetic markers support separation of the myxomycete Lycogala epidendrum into numerous biological species

Arcyria and allied genera: taxonomic backbone and character evolution

Arcyria, one of the most diverse genera of bright-spored myxomycetes, has recently been identified as polyphyletic within the paraphyletic family Arcyriaceae sensu lato. However, due to the high variability and inconsistency of morphological traits in Trichiales, no taxonomic decision has yet been proposed to rectify this situation. A thorough revision of the genus is necessary. To address this, we present results of the extensive taxonomic and geographic sampling of the genus by incorporating sequences of two marker genes from 192 specimens of Arcyria spp. from 19 countries and six continents into the existing three gene phylogenetic backbone of Trichiales. Our phylogenies decisively confirm the polyphyletic nature of Arcyria, with a considerable part of the genus forming a sister clade to Hemitrichia. Consequently, we erect here the new family Hemitrichiaceae and resurrect the genus Heterotrichia to accommodate the second major branch of former Arcyria species. Additionally, we describe the new genus Spiromyxa with intermediate phylogenetic position and unique combination of morphological traits. Furthermore, we show that most of the Arcyria morphospecies included into this study are either species complexes or para- or polyphyletic taxa. Traits, previously thought to delimit the genus Arcyria, show little consistency with the phylogeny. In particular, the expanding, net-like capillitium, attached to the cup or stalk, appears to have been present in the ancestor of three families of Trichiales, afterwards mostly persisted in two of them and evolved into something else in the third. Such traits as ornamentation of capillitium, cup and spores retain their taxonomic value primarily at the species level. However, the colour of the spore mass in fresh condition partially aligns with our phylogenetic results: most of the yellow "Arcyria" species cluster within Heterotrichia, while red and grey species sort mostly into separate subclades within the clade incorporating the remaining species of the genus Arcyria. Citation: Yatsiuk I, Leontyev D, Schnittler M, Ehlers T, Mikryukov V, Kõljalg U (2025). Arcyria and allied genera: taxonomic backbone and character evolution. Fungal Systematics and Evolution 15: 97-118. doi: 10.3114/fuse.2025.15.04.

Not a Lycogala? Investigating the holotype of Lycogala fuscoviolaceum

The myxomycete Lycogala fuscoviolaceum was described by P. Onsberg in 1972 based on a single specimen collected in Nepal. The status of this species remains ambiguous, as no additional findings have been reported since its description. In this study, we re-examined the holotype stored in Copenhagen to determine the true systematic position of L. fuscoviolaceum. Morphological observations revealed features inconsistent with Lycogala, including the dense, cartilaginous cortex, the pseudocapillitium forming vertical bundles, and the thick-walled spores with elongated pore. These characteristics suggest that L. fuscoviolaceum is either a member of the family Reticulariaceae, possibly related to Reticularia or Siphoptychium, or it is not a myxomycete at all. Cross-sections of the cortical structures of L. fuscoviolaceum revealed the presence of cell-like elements arranged in distinct layers. Such elements were absent in Reticularia splendens, Siphoptychium reticulatum, and S. violaceum, but present in L. flavofuscum. Attempts to obtain molecular data from the holotype of L. fuscoviolaceum, including high-throughput sequencing of short fragments, were unsuccessful due to DNA degradation. New findings are required to clarify the taxonomic position of the species.

Species descriptions in myxomycetes - can we settle on rules for good taxonomic practice?

Myxomycetes are a unique branch of life, recognisable by sporophores showing a fungus-like dispersal biology. These structures bear nearly all diagnostic characters for species identification and develop by rapid transformation of plasmodia. During this short period of time, external factors can significantly influence the formation of morphological characters. Therefore, the description of a new species must be carried out with utmost care. Over the last 50 years, approximately 10-15 new species of myxomycetes have been described per year and only some of the latest publications underpin this with molecular data. In this paper, we discuss a set of recommendations for the description of myxomycete species new to science, striving for the following goals: (i) to minimise the number of erroneous descriptions of the species, whose names later have to be put into synonymy; (ii) to make all respective data easily accessible for the scientific community; and (iii) to comply with existing rules of nomenclature. We recommend (1) whenever possible not to describe a new taxon from a single specimen; however, an exception could be made only if supported by molecular data and by unique morphological characters which are unlikely to fall in the range of infraspecific variation of related species; (2) preparing detailed descriptions, including data on developmental stages, microhabitats, ecology, phenology and associated species; (3) providing at least two independent diagnostic characters that tell the new species apart from all others; (4) obtaining a molecular barcode and, whenever possible, providing proof for reproductive isolation of the new species from related taxa; and (5) depositing type specimens in public herbaria. To comply with nomenclatural rules, (6) the new name must be registered in a recognised repository, (7) all published names should be checked for usability before proposing a new name and (8) a unique name should be chosen, preferably highlighting a distinct character of the new species.

A new species of Diacheopsis (Myxomycetes) and a new habitat for myxomycetes

We describe a new species, Diacheopsis resinae (Myxomycetes), collected from a microhabitat new for myxomycetes: stem wounds of coniferous trees (Norway spruce) where the resin is overgrown with a community of resinicolous fungi. The 80 known collections come from the Vosges (France), the Black Forest (Germany), Swabian Alp (Germany), and several localities in Denmark and Norway. Observations, but as well as metabarcoding of substrate samples with fungal (ITS [internal transcribed spacer]), bacterial (16S rDNA), and myxomycete (18S nuc rDNA) primers from eight trunks, revealed the new myxomycete to co-occur with resin-degrading ascomycetes (Infundichalara microchona, Lophium arboricola, Zythia resinae). The gram-negative bacterial genera Endobacter and Sphingomonas were found to be abundant in the substrate and may be a food source for the myxomycete. Fruit bodies were found mostly during the more humid winter season, with a peak in January/February. Partial sequences of two independent molecular markers (18S nuc rDNA, EF1α [elongation factor 1-alpha] gene) were obtained for 41 accessions, which form a monophyletic cluster in a two-gene phylogeny of Stemonititidales but do not group with other species of Diacheopsis, thus rendering this genus paraphyletic. The new species, although exclusively developing sessile sporocarps and morphologically undoubtedly falling into the genus Diacheopsis, is most closely related to species of Lamproderma, especially L. album, L. zonatum, and L. zonatopulchellum. Within D. resinae, three groups can be differentiated, which show nearly complete reproductive isolation, as judged from a recombination analysis of the two unlinked markers and the allelic combinations of the EF1α gene.

The Systematics and Phylogeny of Myxomycetes: Yesterday, Today, and Tomorrow

Myxomycetes are amoeboid fungus-like organisms (Amoebozoa) with a unique life cycle characterized by a great morphological diversity of fruiting bodies. Due to the similarity of these structures to the fruiting bodies of some representatives of Ascomycota and Basidiomycota, myxomycetes have been classified as fungi since the first known scientific description in 1654. Only in the 19th century, when their life cycle was studied, did the difference of this group from fungi become clear. During the same period, microscopic structures of fruiting bodies, as well as ornamentation of the spore surface, began to be considered as diagnostic features. Due to this, in the period from the end of the 19th to the middle of the 20th century, a rather stable system was formed. However, as further studies have shown, both macro- and micromorphological characters are often quite variable, depend on environmental conditions, and often result from convergent evolution, which causes difficulties in defining species and taxonomic units of higher ranks. Since the first decade of the 21st century, due to the development of molecular genetic methods and the accumulation of data on nucleotide sequences of marker genes together with the improvement of microscopic studies, it has been possible to obtain data on the evolutionary relationships of different groups of myxomycetes. A milestone in this process was the publication of the first phylogenetic system of myxomycetes in 2019. This work was the starting point for a number of studies on the relationships between different groups of myxomycetes at a lower taxonomic level. Thus, there has been a surge in the number of studies that bring us closer to constructing a natural system.

Catalogue of fungi in China 4: Didymiaceae and Physaraceae (Myxomycetes)

Myxomycetes play crucial ecological roles, yet their species diversity, distribution, and taxonomic relationships remain poorly understood. In this study, we examined 104 specimens from 19 provinces in China. Through morphological analysis, we identified a group of species with reduced lime formation, a feature typically associated with the Physaraceae, but with key morphological similarities to the Diderma. A comprehensive phylogenetic analysis was conducted using three genes (nSSU, EF-1α, and COI), resulting in a dataset of 452 sequences from 116 species. Notably, we identified a distinct clade within Didymiaceae containing species with fewer lime knots, a trait traditionally linked to Physaraceae. This clade, designated as the new genus Neodiderma, was phylogenetically positioned as a sister group to Diderma, potentially representing a transitional group between Didymiaceae and Physaraceae, supported by both morphological and molecular evidence. Eleven new species - N. macrosporum, N. pseudobisporum, N. verrucocapillitium, N. rigidocapillitium, N. rufum, Physarum guangxiense, P. subviride, P. nigritum, P. biyangense, P. neoovoideum, and P. jilinense - were identified from China, and their phylogenetic positions were analysed. Additionally, N. spumarioides (formerly Diderma spumarioides) was recombined. The new and recombined species were formally described and illustrated, and a key to the sections and species of Neodiderma and Physarum was provided.

A new species of the Trichia botrytis complex from the cloud forest in Ecuador

The paper describes a new myxomycete species, Trichia tuberculata, from the Ecuadorian cloud forest. The phylogeny constructed with nuclear 18S rDNA and mitochondrial 17S rDNA sequences indicates that the taxon is closely related to recently described species T. acetocorticola, T. nubila, and T. pinicola, all within the T. botrytis complex. The morphology of the inner peridium surface and capillitium also aligns T. tuberculata with these species. However, the distinctive tuberculate peridium, short elater tips, and perhaps the distribution range (so far found in the equatorial zone only) distinguish T. tuberculata from related taxa.

Morphological and phylogenetic analyses reveal four species of myxomycetes new to China

Four species of myxomycetes (Arcyria pseudodenudata, Diderma europaeum, Lycogala irregulare, and Trichia armillata) new to China were observed via light microscope and scanning electron microscope, and detailed descriptions and illustrations are provided, along with comparisons with related species. Among them, A. pseudodenudata was discovered for the first time outside of the type locality, D. europaeum was discovered for the first time outside of Europe, and L. irregulare and T. armillata were reported again after being named. Phylogenetic analyses based on nuclear 18S rDNA and elongation factor-1 alpha sequences or nuclear 18S rDNA and cytochrome oxidase subunit I sequences was performed to provide a molecular basis for morphological identification. These specimens were deposited in the Herbarium of Fungi of Nanjing Normal University.

Two New Species of the Genus Diderma (Physarales, Didymiaceae) in China with an Addition to the Distribution

Myxomycetes are an important component of terrestrial ecosystems, and in order to understand their diversity and phylogenetic relationships, taxonomic issues need to be addressed. In our 1985-2021 biodiversity investigations in Shaanxi Province, Jilin Province, the Inner Mongolia Autonomous Region, Hubei Province, and Henan Province, China, Diderma samples were observed on rotten leaves, rotten branches, and dead wood. The samples were studied, based on morphological features coupled with multigene phylogenetic analyses of nSSU, EF-1α, and COI sequence data, which revealed two new species (Diderma shaanxiense sp. nov. and D. clavatocolumellum sp. nov.) and two known species (D. radiatum and D. globosum). In addition, D. radiatum and D. globosum were newly recorded in Henan Province and the Inner Mongolia Autonomous Region, respectively. The paper includes comprehensive descriptions, detailed micrographs, and the outcomes of phylogenetic analyses for both the newly discovered and known species. Additionally, it offers morpho-logical comparisons between the new species and similar ones.

DNA barcodes reliably differentiate between nivicolous species of Diderma (Myxomycetes, Amoebozoa) and reveal regional differences within Eurasia

The nivicolous species of the genus Diderma are challenging to identify, and there are several competing views on their delimitation. We analyzed 102 accessions of nivicolous Diderma spp. that were sequenced for two or three unlinked genes to determine which of the current taxonomic treatments is better supported by molecular species delimitation methods. The results of a haplotype web analysis, Bayesian species delimitation under a multispecies coalescent model, and phylogenetic analyses on concatenated alignments support a splitting approach that distinguishes six taxa: Diderma alpinum, D. europaeum, D. kamchaticum, D. meyerae, D. microcarpum and D. niveum. The first two approaches also support the separation of Diderma alpinum into two species with allopatric distribution. An extended dataset of 800 specimens (mainly from Europe) that were barcoded with 18S rDNA revealed only barcode variants similar to those in the species characterized by the first data set, and showed an uneven distribution of these species in the Northern Hemisphere: Diderma microcarpum and D. alpinum were the only species found in all seven intensively sampled mountain regions. Partial 18S rDNA sequences serving as DNA barcodes provided clear signatures that allowed for unambiguous identification of the nivicolous Diderma spp., including two putative species in D. alpinum.

Dataset of barcoded Reticulariaceae: ten years of DNA sequencing

Background

As a result of the ten years (2012-2022) work under the critical revision of the genera of Reticulariaceae, a set of papers was published. Collection data of hundreds of specimens, used as a material for these studies, were provided as supplements of corresponding papers, but remained unpublished in biodiversity databases.

New information

Here, we represent an occurrence dataset "Barcoded Reticulariaceae of the World", published in GBIF. It includes data on 523 myxomycete collections (including 36 types) gathered from five continents and spanning 24 countries. The dataset encompasses 43 distinct species and one subspecies of myxomycetes, including rare, endemic, and recently-described taxa. Species included to the database mainly belong to the genera Alwisia, Lycogala, Reticularia, Siphoptychium, Thecotubifera and Tubifera (Reticulariaceae), but as well Lindbladia and Licaethalium (Cribrariaceae). Nearly all of the research material, with the exception of several old collections, underwent molecular barcoding, primarily involving the 18S rDNA gene, but also the elongation factor 1α gene and mitochondrial cytochrome oxidase subunit I gene. For those sequences that are stored in the NCBI GenBank, accession numbers are provided in the dataset. Newly-described species make up a significant part of the studied herbarium collections; many of them can be characterised as common for their region. A particularly high level of taxonomic novelty is observed in Australia, which may be explained by the endemism of the local myxomycete biota.

Tasmaniomyxa umbilicata, a new genus and new species of myxomycete from Tasmania

A new genus and species of myxomycete, Tasmaniomyxa umbilicata, is described based on numerous observations in Tasmania and additional records from southeastern Australia and New Zealand. The new taxon is characterized by an unusual combination of characters from two families: Lamprodermataceae and Didymiaceae. With Lamprodermataceae the species shares limeless sporocarps, a shining membranous peridium, an epihypothallic stalk, and a cylindrical columella. Like Didymiaceae, it has a soft, flaccid, sparsely branched capillitium, with rough tubular threads that contain fusiform nodes and are firmly connected to the peridium. Other characters of T. umbilicata that also occur in many Didymiaceae are the peridium dehiscing into petaloid lobes, the yellow, motile plasmodium, and the spores ornamented with larger, grouped and smaller, scattered warts. The transitional position of the new taxon is reflected by a three-gene phylogeny, which places T. umbilicata at the base of the branch of all lime-containing Physarales, thus justifying its description as a monotypic genus.