Didymium pseudonivicola: A new myxomycete from the austral Andes emerges from broad-scale morphological and molecular analyses of D. nivicola collections

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.

Didymium arenosum, a myxomycete new to science from the confluence of deserts in northwestern China

A new myxomycete species, Didymium arenosum, was described based on morphological evidence and phylogenetic analyses. The species was discovered in the arid region at the confluence of the Badain Jaran desert and Tengger desert on the leaves of Betula platyphylla and was cultivated in a moist chamber culture. Morphologically, the species is distinguished by the greenish-yellow calcium carbonate crystals on the surface and the spores covered with small warts, some of which are connected into a short line. A phylogenetic analysis of D. arenosum strongly supports its classification as a separate clade. The spore to spore agar culture of D. arenosum requires 23 days, and this study provides a detailed description of its life cycle.